We have examined the theoretical implications of combining two main and three auxiliary ligands to form several Ir(Ⅲ)complexes featuring a transition metal as their core atom to identify some appropriate organic ligh...We have examined the theoretical implications of combining two main and three auxiliary ligands to form several Ir(Ⅲ)complexes featuring a transition metal as their core atom to identify some appropriate organic lightemitting diode(OLED)materials.By utilizing electronic structure,frontier molecular orbitals,minimum single-line absorption,triplet excited states,and emission spectral data derived from the density functional theory,the usefulness of these Ir(Ⅲ)complexes,including(piq)_(2)Ir(acac),(piq)_(2)Ir(tmd),(piq)_(2)Ir(tpip),(fpiq)_(2)Ir(acac),(fpiq)_(2)Ir(tmd),and(fpiq)_(2)Ir(tpip),in OLEDs was examined,where piq=1-phenylisoquinoline,fpiq=1-(4-fluorophenyl)isoquinoline,acac=(3Z)-4-hydroxypent-3-en-2-one,tmd=(4Z)-5-hydroxy-2,2,6,6-tetramethylhept-4-en-3-one,and tpip=tetraphenylimido-diphosphonate.These complexes all have low-efficiency roll-off properties,especially(fpiq)_(2)Ir(tpip).Some researchers have successfully synthesized complexes extremely similar to(piq)_(2)Ir(acac)through the Suzuki-Miyaura coupling reaction.展开更多
Polarons are widely considered to play a crucial role in the charge transport and photocatalytic performance of materials,but the mechanisms of their formation and the underlying driving factors remain a matter of con...Polarons are widely considered to play a crucial role in the charge transport and photocatalytic performance of materials,but the mechanisms of their formation and the underlying driving factors remain a matter of controversy.This study delves into the formation of polarons in different crystalline forms of TiO_(2) and their connection with the materials'structure.By employing density functional theory calculations with on-site Coulomb interaction correction(DFT+U),we provide a detailed analysis of the electronic polarization behavior in the anatase and rutile forms of TiO_(2).We focus on the polarization properties of defect-induced and photoexcited excess electrons on various TiO_(2) surfaces.The results reveal that the defect electrons can form small polarons on the anatase TiO_(2)(101)surface,while on the rutile TiO_(2)(110)surface,both small and large polarons(hybrid-state polarons)are formed.Photoexcited electrons are capable of forming both small and large polarons on the surfaces of both crystal types.The analysis indicates that the differences in polaron distribution are primarily determined by the intrinsic properties of the crystals;the structural and symmetry differences between anatase and rutile TiO_(2) lead to the distinct polaron behaviors.Further investigation suggests that the polarization behavior of defect electrons is also related to the arrangement of electron orbitals around the Ti atoms,while the polarization of photoexcited electrons is mainly facilitated by the lattice distortions.These findings elucidate the formation mechanisms of different types of polarons and may contribute to understanding the performance of TiO_(2)in different fields.展开更多
Pyrite （FeS2） bulk and （100） surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2 （100） surface, the...Pyrite （FeS2） bulk and （100） surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2 （100） surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe2+ and S2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference. The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.展开更多
Based on the pseudo potential plane-wave method of density functional theory （DFT）, Ti1-xNbxAk （x=0, 0.062 5, 0.083 3, 0.125, 0.250） crystals＇ geometry structure, elastic constants, electronic structure and Mulli...Based on the pseudo potential plane-wave method of density functional theory （DFT）, Ti1-xNbxAk （x=0, 0.062 5, 0.083 3, 0.125, 0.250） crystals＇ geometry structure, elastic constants, electronic structure and Mulliken populations were calculated, and the effects of doping on the geometric structure, electronic structure and bond strength were systematically analyzed. The results show that the influence of Nb on the geometric structure is little in terms of the plasticity, and with the increase of Nb content, the covalent bond strength remarkably reduces, and Ti-Al, Nb-M （M=Ti, Al） and other hybrid bonds enhance; meanwhile, the peak district increases and the pseudo-energy gap first decreases and then increases, the overall band structure narrows, the covalent bond and direction of bonds reduce. The population analysis also shows that the results are consistent with the electronic structure analysis. The density of states of TiAINb shows that Nb doping can enhance the activity of Al and benefit the form of Al2O3 film. All the calculations reveal that the room temperature plasticity and the antioxidation properties of the compounds can be improved with the Nb content of 8.33%-12.5% （mole fraction）.展开更多
Structural and electronic properties of Pb_(n)Ag_(n)(n=2–12)clusters were investigated by density functional theory with generalized gradient approximation at BLYP level in DMol3 program package.The optimized bimetal...Structural and electronic properties of Pb_(n)Ag_(n)(n=2–12)clusters were investigated by density functional theory with generalized gradient approximation at BLYP level in DMol3 program package.The optimized bimetallic Pb_(n)Ag_(n)(n=2–12)clusters were viewed as the initial structures,then,those were calculated by ab initio molecular dynamics(AIMD)to search possible global minimum energy structures of Pb_(n)Ag_(n)clusters,finally,the ground state structures of Pb_(n)Ag_(n)(n=2–12)clusters were achieved.According to the structural evolution of lowest energy structures,Ag atoms prefer gather in the central sites while Pb atoms prefer external positions in Pb_(n)Ag_(n)(n=2–12)clusters,which is in excellent agreement with experimental results from literature and the application in metallurgy.The average binding energies,HOMO-LUMO gaps,vertical ionization potentials,vertical electron affinities,chemical hardnessη,HOMO orbits,LUMO orbits and density of states of Pb_(n)Ag_(n)(n=2–12)clusters were calculated.The results indicate that the values of HOMO-LUMO gaps,vertical ionization potentials,vertical electron affinities and chemical hardnessηshow obvious odd-even oscillations when n≤5,Pb_(n)Ag_(n)(n=2–12)clusters become less chemically stable and show insulator-to-metal transition with the variation of cluster size n,Pb_(n)Ag_(n)(n≥9)cluster are good candidates to study the properties of PbAg alloys.Those can be well explained by the density of states(DOS)distributions of Pb atoms and Ag atoms between–0.5 Ha and 0.25 Ha in Pb_(n)Ag_(n)(n=2–12)clusters.展开更多
The structures, infrared spectra and cation stability of seven 5,5′-azotetrazolate nonmetallic salts are investigated by using B3LYP method with 6-311+G (d) basis set. The salts are guanidinium (GZT), aminoguanidiniu...The structures, infrared spectra and cation stability of seven 5,5′-azotetrazolate nonmetallic salts are investigated by using B3LYP method with 6-311+G (d) basis set. The salts are guanidinium (GZT), aminoguanidinium (AGZT), diaminoguanidinium (DAGZT), triaminoguanidinium (TAGZT), azidoformamidinium (AFZT), ammonium (AZT), and hydrazinium (HZT), respectively. The calculated results indicate that the carbon and nitrogen atoms of the cations in seven nonmetallic salts are characterized to be sp2 hybrid atoms, and the ranges of characteristic absorption peaks in IR spectra of the seven nonmetallic salts are approximative consistent. All their cations are stable and their stabilities decrease with the increase in their nitrogen contents.展开更多
Malachite,being highly hydrophilic and difficult to be floated conventionally,is usually beneficiated by sulfidation flotation in industry.However,the complex crystal structure of malachite leads to the formation of v...Malachite,being highly hydrophilic and difficult to be floated conventionally,is usually beneficiated by sulfidation flotation in industry.However,the complex crystal structure of malachite leads to the formation of various fracture surfaces with distinct properties during crushing and grinding,resulting in surface anisotropy.In this study,we explored the surface anisotropy of malachite and further investigated its sulfidation mechanism from the coordination chemistry perspective,considering the influence of the Jahn-Teller effect on malachite sulfidation.Computational results reveal that the penta-coordinated Cu ions on the malachite(201)and(010)surfaces exhibit stronger activity compared to those on the malachite(201)surface.Additionally,the tetra-coordinated structure formed by HS^(−)adsorption on the malachite(010)and(201)surfaces is more stable,with more negative adsorption energy,compared to the hexa coordinated structure formed by HS−adsorption on the(201)surface.The sulfidized malachite surface has an additional pair ofπelectron and smaller HOMO(highest occupied molecular orbital)-LUMO(lowest unoccupied molecular orbital)gap with xanthate molecules,causing strongerπbackbonding with xanthate.This study provides new insights into the surface sulfidation mechanism of malachite and offers a theoretical reference for the design of targeted flotation reagents.展开更多
The intricate grinding process exposes various cleavage surfaces of mineral particles.This paper systematically investigates the structural characteristics of exposed malachite crystal surfaces and the adsorption beha...The intricate grinding process exposes various cleavage surfaces of mineral particles.This paper systematically investigates the structural characteristics of exposed malachite crystal surfaces and the adsorption behavior and mechanism of hydroxamic acid and water molecules using first-principle density functional theory.The study reveals anisotropic surface energies among crystal surfaces,ranked as(201)>(100)>(110)>(001)>(010)>(201).The adsorption of hydroxamic acid and water molecules on malachite surfaces also exhibited anisotropy.The difference in adsorption strength between hydroxamic acid and water molecules on the six exposed surfaces followed the order of(110)>(100)>(010)>(001)>(201)>(201),and the resistance of water molecules to the adsorption of hydroxamic acid on the six exposed surfaces was(110)>(201)>(010)>(201)>(001)>(100).It indicates that the reagent exhibits a strong competitive advantage in adsorption on the(100)surface,and the hindrance of water molecules to reagent adsorption is relatively small,which is favorable for flotation.This study provides theoretical references and innovative insights for the precise design of flotation reagents,as well as for the meticulous optimization of mineral surface interfaces,with the objective of enhancing flotation separation.展开更多
The ReaxFF can describe the properties of energetic materials(EMs)at equilibrium state,but does not work properly in simulating high-energy particle irradiation process because of its weak short-range interaction.In t...The ReaxFF can describe the properties of energetic materials(EMs)at equilibrium state,but does not work properly in simulating high-energy particle irradiation process because of its weak short-range interaction.In this paper,a modification was made for such a potential by connecting ZieglerBiersack-Littmark(ZBL)potential to ReaxFF-lg through comparing to Density Functional Theory(DFT)results to accurately describe short-range interactions.After modification,the newly fitted ReaxFF-lg/ZBL potential predicts better the equation of state for EMs In displacement cascade simulations,comparing to results from ab initio molecular dynamics(AIMD),ReaxFF-lg/ZBL presented the similar transferred energy from a primary knock-on atom to surrounding atoms,better than the original ReaxFF-lg potential.Further large-scale displacement cascade simulations indicated ReaxFF-lg/ZBL could be applied for cascade simulations with PKA energy from less than 1 keV to high energy(e.g.35 keV)cases,which is suitable for effectively simulating high-energy displacement cascades in EMs using molecular dynamics method.展开更多
Traditional selection of combustion catalysis is time-consuming and labor-intensive.Theoretical calculation is expected to resolve this problem.The adsorption energy of HMX and O atoms on 13 metal oxides was calculate...Traditional selection of combustion catalysis is time-consuming and labor-intensive.Theoretical calculation is expected to resolve this problem.The adsorption energy of HMX and O atoms on 13 metal oxides was calculated using DMol3,since HMX and O are key substances in decomposition process.And the relationship between the adsorption energy of HMX,O on metal oxides(TiO_(2),Al_(2)O_(3),PbO,CuO,Fe_(2)O_(3),Co_(3)O_(4),Bi_(2)O_(3),NiO)and experimental T30 values(time required for the decomposition depth of HMX to reach 30%)was depicted as volcano plot.Thus,the T30 values of other metal oxides was predicted based on their adsorption energy on volcano plot and validated by previous experimental data.Further,the adsorption energy of HMX on ZrO_(2)and MnO_(2)was predicted based on the linear relationship between surface energy and adsorption energy,and T30 values were estimated based on volcano plot.The apparent activation energy data of HMX/MgO,HMX/SnO_(2),HMX/ZrO_(2),and HMX/MnO_(2)obtained from DSC experiments are basically consistent with our predicted T30 values,indicating that it is feasible to predict the catalytic activity based on the adsorption calculation,and it is expected that these simple structural properties can predict adsorption energy to reduce the large quantities of computation and experiment cost.展开更多
Platinum(Pt)-based noble metal catalysts(PGMs)are the most widely used commercial catalysts,but they have the problems of high cost,low reserves,and susceptibility to small-molecule toxicity.Transition metal oxides(TM...Platinum(Pt)-based noble metal catalysts(PGMs)are the most widely used commercial catalysts,but they have the problems of high cost,low reserves,and susceptibility to small-molecule toxicity.Transition metal oxides(TMOs)are regarded as potential substitutes for PGMs because of their stability in oxidizing environments and excellent catalytic performance.In this study,comprehensive investigation into the influence of elastic strains on the adsorption energies of carbon(C),hydrogen(H)and oxygen(O)on TMOs was conducted.Based on density functional theory(DFT)calculations,these effects in both tetragonal structures(PtO_(2),PdO_(2))and hexagonal structures(ZnO,CdO),along with their respective transition metals were systematically explored.It was identified that the optimal adsorption sites on metal oxides pinpointed the top of oxygen or the top of metal atom,while face-centered cubic(FCC)and hexagonal close-packed(HCP)holes were preferred for the transition metals.Furthermore,under the influence of elastic strains,the results demonstrated significant disparities in the adsorption energies of H and O between oxides and transition metals.Despite these differences,the effect of elastic strains on the adsorption energies of C,H and O on TMOs mirrored those on transition metals:adsorption energies increased under compressive strains,indicating weaker adsorption,and decreased under tension strains,indicating stronger adsorption.This behavior was rationalized based on the d-band model for adsorption atop a metallic atom or the p-band model for adsorption atop an oxygen atom.Consequently,elastic strains present a promising avenue for tailoring the catalytic properties of TMOs.展开更多
To enhance the separation selectivity of Mg-MOF-74 towards CO_(2) in a CO_(2)/N_(2) mixture,a series of Mg-MOF-74 and Ni_(x)/Mg_(1-x)-MOF-74 adsorbents were prepared by solvothermal synthesis in this paper.It was foun...To enhance the separation selectivity of Mg-MOF-74 towards CO_(2) in a CO_(2)/N_(2) mixture,a series of Mg-MOF-74 and Ni_(x)/Mg_(1-x)-MOF-74 adsorbents were prepared by solvothermal synthesis in this paper.It was found that the adsorption capacity of Mg-MOF-74 for CO_(2) could be effectively increased by optimizing the amount of acetic acid.On this basis,the bimetal MOF-74 adsorbent was prepared by metal modification.The multi-component dynamic adsorption penetration analysis was utilized to examine the CO_(2) adsorption capacity and CO_(2)/N_(2) selectivity of the diverse adsorbent materials.The results showed that Ni0.11/Mg0.89-MOF-74 showed a CO_(2) adsorption capacity of 7.02 mmol/g under pure CO_(2) atmosphere and had a selectivity of 20.50 for CO_(2)/N_(2) under 15% CO_(2)/85%N_(2) conditions,which was 10.2% and 18.02% higher than that of Mg-MOF-74 respectively.Combining XPS,SEM and N_(2) adsorption-desorption characterization analysis,it was attributed to the effect of the more stable unsaturated metal sites Ni into the Mg-MOF-74 on the pore structure and the synergistic interaction between the two metals.Density Functional Theory(DFT)simulations revealed that the synergistic interaction between modulated the electrostatic potential strength and gradient of the material,which was more favorable for the adsorption of CO_(2) molecules with small diameters and large quadrupole moment.In addition,the Ni0.11/Mg0.89-MOF-74 showed commendable cyclic stability,underscoring its promising potential for practical applications.展开更多
The spin caloritronic properties of the Janus VSTe monolayer were investigated using density functional theory(DFT)and the non-equilibrium Green’s function(NEGF)method,implemented in the Atomistix Toolkit(ATK)package...The spin caloritronic properties of the Janus VSTe monolayer were investigated using density functional theory(DFT)and the non-equilibrium Green’s function(NEGF)method,implemented in the Atomistix Toolkit(ATK)package.Our study revealed significant spin-splitting within the Janus VSTe monolayer,which induced spin currents under a temperature gradient across the device.By applying a 1%tensile strain,the Janus VSTe monolayer exhibited a perfect thermal spin filtering effect(SFE),with the spin-up current nearly suppressed to zero.Both the unstrained and strained Janus VSTe monolayers demonstrated excellent spin caloritronic properties,with spin figures of merit of 10.915 and 8.432 at an average temperature of 100 K,respectively.Notably,these properties were found to be sensitive to temperature,performing optimally at lower temperatures.These results suggest a promising avenue for designing spin caloritronic devices aimed at efficient waste heat recovery.展开更多
Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe...Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe 3d, while that of hexagonal pyrrhotite is from Fe 3d, Fe 3p and S 3s. The hexagonal pyrrhotite is more reactive than monoclinic pyrrhotite because of large density of states near the Fermi level. The hexagonal pyrrhotite shows antiferromagnetism. S—Fe bonds mainly exist in monoclinic pyrrhotite as the covalent bonds, while hexagonal pyrrhotite has no covalency. The main contributions of higest occupied molecular orbital(HOMO) and lowest unoccupied molecular obital(LUMO) for monoclinic pyrrhotite come from S and Fe. The main contribution of HOMO for hexagonal pyrrhotite comes from Fe, while that of LUMO comes from S. The coefficient of Fe atom is much larger than that of S atom of HOMO for hexagonal pyrrhotite, which contributes to the adsorption of Ca OH+ on the surface of hexagonal pyrrhotite when there is lime. As a result, lime has the inhibitory effect on the floatation of hexagonal pyrrhotite and the coefficient of Fe is very close to that of S for monoclinic pyrrhotite. Therefore, the existence of S prevents the adsorption of Ca OH+on the surface of monoclinic pyrrhotite, which leads to less inhibitory effect on the flotation of monoclinic pyrrhotite.展开更多
Na-ion diffusion kinetics is a key factor that decided the charge/discharge rate of the electrode materials in Na-ion batteries.In this work,two extreme concentrations of NaMnO_(2) and Na_(2/3)Li_(1/6)Mn_(5/6)O_(2) ar...Na-ion diffusion kinetics is a key factor that decided the charge/discharge rate of the electrode materials in Na-ion batteries.In this work,two extreme concentrations of NaMnO_(2) and Na_(2/3)Li_(1/6)Mn_(5/6)O_(2) are considered,namely,the vacancy migration of Na ions in the fully intercalated and the migration of Na ions in the fully de-intercalated.The Na-vacancy and Na^(+)distribution in NaMnO_(2) migrated along oxygen dumbbell hop(ODH)and tetrahedral site hop(TSH),and the migration energy barriers were 0.374 and 0.296 eV,respectively.In NaLi_(1/6)Mn_(5/6)O_(2),the inhomogeneity of Li doping leads to the narrowing of the interlayer spacing by 0.9%and the increase of the energy barrier by 53.8%.On the other hand,due to the alleviation of Jahn-Teller effect of neighboring Mn,the bonding strength of Mn-O was enhanced,so that the energy barrier of path 2-3 in Mn-L1 and Mn-L2 was the lowest,which was 0.234 and 0.424 eV,respectively.In Na_(1/6)Li_(1/6)Mn_(5/6)O_(2),the migration energy barriers of Na-L2 and Na-L3 are 1.233 and 0.779 eV,respectively,because Li+migrates from the transition(TM)layer to the alkali metal(AM)layer with Na^(+)migration,which requires additional energy.展开更多
In this work,the Fukui functions of the two ~2P resonance states of Be,a ~2P resonance state of Mg~–,and a ~2D resonance state of Ca~– have been determined.The trajectories of these resonance states,in conjunction w...In this work,the Fukui functions of the two ~2P resonance states of Be,a ~2P resonance state of Mg~–,and a ~2D resonance state of Ca~– have been determined.The trajectories of these resonance states,in conjunction with the complex rotation of the Hamiltonian,were used to determine their wave functions.The electron densities,Fukui functions,and values of the hyper-radius<r^2>were computed from these wave functions.The Fukui functions have negative regions in the valence shell in addition to the inner shell regions,indicating screening effects of the outer temporary electron.Selected configuration interactions with up to quadruple excitations were used along the trajectories and for computing the final wave function.Based on this data,the densities,Fukui functions,and<r^2>were calculated.展开更多
Quantitative correlation of several theoretical electrophilicity measures over different families of organic compounds are examined relative to the experimental values of Mayr et al.Notably,the ability to predict thes...Quantitative correlation of several theoretical electrophilicity measures over different families of organic compounds are examined relative to the experimental values of Mayr et al.Notably,the ability to predict these values accurately will help to elucidate the reactivity and selectivity trends observed in charge-transfer reactions.A crucial advantage of this theoretical approach is that itprovides this information without the need of experiments,which are often demanding and time-consuming.Here,two different types of electrophilicity measures were analyzed.First,models derived from conceptual density functional theory(c-DFT),including Parr's original proposal and further generalizations of this index,are investigated.For instance,the approaches of Gázquez et al.and Chamorro et al.are considered,whereby it is possible to distinguish between processes in which a molecule gains or loses electrons.Further,we also explored two novel electrophilicity definitions.On one hand,the potential of environmental perturbations to affect electron incorporation into a system is analyzed in terms of recent developments in c-DFT.These studies highlight the importance of considering the molecular surroundings when a consistent description of chemical reactivity is needed.On the other hand,we test a new definition of electrophilicity that is free from inconsistencies(so-called thermodynamic electrophilicity).This approach is based on Parr's pioneering insights,though it corrects issues present in the standard working expression for the calculation of electrophilicity.Additionally,we use machine-learning tools(i.e.,symbolic regression)to identify the models that best fit the experimental values.In this way,the best possible description of the electrophilicity values in terms of different electronic structure quantities is obtained.Overall,this straightforward approach enables one to obtain good correlations between the theoretical and experimental quantities by using the simple,yet powerful,interpretative advantage of c-DFT methods.In general,we observed that the correlations found at the HF/6-31 G(d)level of theory are of semi-quantitative value.To obtain more accurate results,we showed that working with families of compounds with similar functional groups is indispensable.展开更多
The equilibrium lattice parameters, electronic structure, bulk modulus, Debye temperature, heat capacity and Gibbs energy of TiB and TiB2 were investigated using the pseudopotential plane-wave method based on density ...The equilibrium lattice parameters, electronic structure, bulk modulus, Debye temperature, heat capacity and Gibbs energy of TiB and TiB2 were investigated using the pseudopotential plane-wave method based on density functional theory (DFT) and the improved quasi-harmonic Debye method. The results show that the total density of states (DOS) of TiB2 is mainly provided by the orbit hybridization of Ti-3d and B-2p states, and the total DOS of TiB is mainly provided by the hybrids bond of Ti-3d and B-2p below the Fermi level and Ti—Ti bond up to the Fermi level. The Ti—B hybrid bond in TiB2 is stronger than that in TiB. Finally, the enthalpy of formation at 0 K, heat capacity and Gibbs free energy of formation at various temperatures were determined. The calculated results are in excellent agreement with the available experimental data.展开更多
The molecular structure of cyclohexanone was calculated by the B3LYP density functional model with 6-31G(d,p)and 6-311++G(d,p)basis set by Gaussian program.The results from natural bond orbital(NBO)analysis have been ...The molecular structure of cyclohexanone was calculated by the B3LYP density functional model with 6-31G(d,p)and 6-311++G(d,p)basis set by Gaussian program.The results from natural bond orbital(NBO)analysis have been analyzed in terms of the hybridization of atoms and the electronic structure of the title molecule.The electron density based local reactivity descriptors such as Fukui functions were calculated.The dipole moment(μ)and polarizability(α),anisotropy polarizability(Δα)and first order hyperpolarizability(βtot)of the molecule have been reported.Thermodynamic properties of the title compound were calculated at different temperatures.展开更多
文摘We have examined the theoretical implications of combining two main and three auxiliary ligands to form several Ir(Ⅲ)complexes featuring a transition metal as their core atom to identify some appropriate organic lightemitting diode(OLED)materials.By utilizing electronic structure,frontier molecular orbitals,minimum single-line absorption,triplet excited states,and emission spectral data derived from the density functional theory,the usefulness of these Ir(Ⅲ)complexes,including(piq)_(2)Ir(acac),(piq)_(2)Ir(tmd),(piq)_(2)Ir(tpip),(fpiq)_(2)Ir(acac),(fpiq)_(2)Ir(tmd),and(fpiq)_(2)Ir(tpip),in OLEDs was examined,where piq=1-phenylisoquinoline,fpiq=1-(4-fluorophenyl)isoquinoline,acac=(3Z)-4-hydroxypent-3-en-2-one,tmd=(4Z)-5-hydroxy-2,2,6,6-tetramethylhept-4-en-3-one,and tpip=tetraphenylimido-diphosphonate.These complexes all have low-efficiency roll-off properties,especially(fpiq)_(2)Ir(tpip).Some researchers have successfully synthesized complexes extremely similar to(piq)_(2)Ir(acac)through the Suzuki-Miyaura coupling reaction.
文摘Polarons are widely considered to play a crucial role in the charge transport and photocatalytic performance of materials,but the mechanisms of their formation and the underlying driving factors remain a matter of controversy.This study delves into the formation of polarons in different crystalline forms of TiO_(2) and their connection with the materials'structure.By employing density functional theory calculations with on-site Coulomb interaction correction(DFT+U),we provide a detailed analysis of the electronic polarization behavior in the anatase and rutile forms of TiO_(2).We focus on the polarization properties of defect-induced and photoexcited excess electrons on various TiO_(2) surfaces.The results reveal that the defect electrons can form small polarons on the anatase TiO_(2)(101)surface,while on the rutile TiO_(2)(110)surface,both small and large polarons(hybrid-state polarons)are formed.Photoexcited electrons are capable of forming both small and large polarons on the surfaces of both crystal types.The analysis indicates that the differences in polaron distribution are primarily determined by the intrinsic properties of the crystals;the structural and symmetry differences between anatase and rutile TiO_(2) lead to the distinct polaron behaviors.Further investigation suggests that the polarization behavior of defect electrons is also related to the arrangement of electron orbitals around the Ti atoms,while the polarization of photoexcited electrons is mainly facilitated by the lattice distortions.These findings elucidate the formation mechanisms of different types of polarons and may contribute to understanding the performance of TiO_(2)in different fields.
文摘Pyrite （FeS2） bulk and （100） surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2 （100） surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe2+ and S2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference. The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.
基金Project(07JJ3102) supported by Hunan Provincial Natural Science Foundation,ChinaProject(k0902132-11) supported by Changsha Municipal Science and Technology,China
文摘Based on the pseudo potential plane-wave method of density functional theory （DFT）, Ti1-xNbxAk （x=0, 0.062 5, 0.083 3, 0.125, 0.250） crystals＇ geometry structure, elastic constants, electronic structure and Mulliken populations were calculated, and the effects of doping on the geometric structure, electronic structure and bond strength were systematically analyzed. The results show that the influence of Nb on the geometric structure is little in terms of the plasticity, and with the increase of Nb content, the covalent bond strength remarkably reduces, and Ti-Al, Nb-M （M=Ti, Al） and other hybrid bonds enhance; meanwhile, the peak district increases and the pseudo-energy gap first decreases and then increases, the overall band structure narrows, the covalent bond and direction of bonds reduce. The population analysis also shows that the results are consistent with the electronic structure analysis. The density of states of TiAINb shows that Nb doping can enhance the activity of Al and benefit the form of Al2O3 film. All the calculations reveal that the room temperature plasticity and the antioxidation properties of the compounds can be improved with the Nb content of 8.33%-12.5% （mole fraction）.
基金Project(51664032)supported by the Regional Foundation of the National Natural Science Foundation of ChinaProject(51474116)supported by the General Program of the National Natural Science Foundation of China+5 种基金Project(U1502271)supported by the Joint Foundation of the NSFC-Yunnan Province,ChinaProject(2014HA003)supported by the Cultivating Plan Program for the Leader in Science and Technology of Yunnan Province,ChinaProject(2014RA4018)supported by the Program for Nonferrous Metals Vacuum Metallurgy Innovation Team of Ministry of Science and Technology,ChinaProject(2016YFC0400404)supported by the National Key Research and Development Program of ChinaProject(51504115)supported by the Youth Program of National Natural Science Foundation of ChinaProject(IRT_17R48)supported by the Program for Innovative Research Team in University of Ministry of Education of China
文摘Structural and electronic properties of Pb_(n)Ag_(n)(n=2–12)clusters were investigated by density functional theory with generalized gradient approximation at BLYP level in DMol3 program package.The optimized bimetallic Pb_(n)Ag_(n)(n=2–12)clusters were viewed as the initial structures,then,those were calculated by ab initio molecular dynamics(AIMD)to search possible global minimum energy structures of Pb_(n)Ag_(n)clusters,finally,the ground state structures of Pb_(n)Ag_(n)(n=2–12)clusters were achieved.According to the structural evolution of lowest energy structures,Ag atoms prefer gather in the central sites while Pb atoms prefer external positions in Pb_(n)Ag_(n)(n=2–12)clusters,which is in excellent agreement with experimental results from literature and the application in metallurgy.The average binding energies,HOMO-LUMO gaps,vertical ionization potentials,vertical electron affinities,chemical hardnessη,HOMO orbits,LUMO orbits and density of states of Pb_(n)Ag_(n)(n=2–12)clusters were calculated.The results indicate that the values of HOMO-LUMO gaps,vertical ionization potentials,vertical electron affinities and chemical hardnessηshow obvious odd-even oscillations when n≤5,Pb_(n)Ag_(n)(n=2–12)clusters become less chemically stable and show insulator-to-metal transition with the variation of cluster size n,Pb_(n)Ag_(n)(n≥9)cluster are good candidates to study the properties of PbAg alloys.Those can be well explained by the density of states(DOS)distributions of Pb atoms and Ag atoms between–0.5 Ha and 0.25 Ha in Pb_(n)Ag_(n)(n=2–12)clusters.
文摘The structures, infrared spectra and cation stability of seven 5,5′-azotetrazolate nonmetallic salts are investigated by using B3LYP method with 6-311+G (d) basis set. The salts are guanidinium (GZT), aminoguanidinium (AGZT), diaminoguanidinium (DAGZT), triaminoguanidinium (TAGZT), azidoformamidinium (AFZT), ammonium (AZT), and hydrazinium (HZT), respectively. The calculated results indicate that the carbon and nitrogen atoms of the cations in seven nonmetallic salts are characterized to be sp2 hybrid atoms, and the ranges of characteristic absorption peaks in IR spectra of the seven nonmetallic salts are approximative consistent. All their cations are stable and their stabilities decrease with the increase in their nitrogen contents.
基金Projects(52074356,U22A20170)supported by the National Natural Science Foundation of ChinaProject(2022YFC2904503)supported by the National Key R&D Program of China+4 种基金Project(2023SK2061)supported by the Special Fund for the Construction of Hunan Innovative Province,ChinaProject(2023CXQD002)supported by the Innovation-driven Project of Central South University,ChinaProject(2022RC1183)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProject(kq2009005)supported by the Changsha Science and Technology Project(Changsha Outstanding Innovative Youth Training Program),ChinaProject supported by the High-performance Computing Centers of Central South University,China。
文摘Malachite,being highly hydrophilic and difficult to be floated conventionally,is usually beneficiated by sulfidation flotation in industry.However,the complex crystal structure of malachite leads to the formation of various fracture surfaces with distinct properties during crushing and grinding,resulting in surface anisotropy.In this study,we explored the surface anisotropy of malachite and further investigated its sulfidation mechanism from the coordination chemistry perspective,considering the influence of the Jahn-Teller effect on malachite sulfidation.Computational results reveal that the penta-coordinated Cu ions on the malachite(201)and(010)surfaces exhibit stronger activity compared to those on the malachite(201)surface.Additionally,the tetra-coordinated structure formed by HS^(−)adsorption on the malachite(010)and(201)surfaces is more stable,with more negative adsorption energy,compared to the hexa coordinated structure formed by HS−adsorption on the(201)surface.The sulfidized malachite surface has an additional pair ofπelectron and smaller HOMO(highest occupied molecular orbital)-LUMO(lowest unoccupied molecular orbital)gap with xanthate molecules,causing strongerπbackbonding with xanthate.This study provides new insights into the surface sulfidation mechanism of malachite and offers a theoretical reference for the design of targeted flotation reagents.
基金Project(52074356)supported by the National Natural Science Foundation of ChinaProject(BGRIMM-KJSKL-2023-06)supported by the Open Foundation of State Key Laboratory of Mineral Processing,China+4 种基金Project(2022RC1183)supported by the Science and Technology Innovation Program of Hunan Province,ChinaProject(kq2009095)supported by the Changsha Science and Technology Project(Outstanding Innovative Youth Training Program),ChinaProject(2023CXQD002)supported by the Innovation Driven Program of Central South University,ChinaProject(B14034)supported by the National“111”Project,ChinaProject(2024ZZTS0655)supported by the Independent Exploration and Innovation Project for Graduate Students of Central South University,China。
文摘The intricate grinding process exposes various cleavage surfaces of mineral particles.This paper systematically investigates the structural characteristics of exposed malachite crystal surfaces and the adsorption behavior and mechanism of hydroxamic acid and water molecules using first-principle density functional theory.The study reveals anisotropic surface energies among crystal surfaces,ranked as(201)>(100)>(110)>(001)>(010)>(201).The adsorption of hydroxamic acid and water molecules on malachite surfaces also exhibited anisotropy.The difference in adsorption strength between hydroxamic acid and water molecules on the six exposed surfaces followed the order of(110)>(100)>(010)>(001)>(201)>(201),and the resistance of water molecules to the adsorption of hydroxamic acid on the six exposed surfaces was(110)>(201)>(010)>(201)>(001)>(100).It indicates that the reagent exhibits a strong competitive advantage in adsorption on the(100)surface,and the hindrance of water molecules to reagent adsorption is relatively small,which is favorable for flotation.This study provides theoretical references and innovative insights for the precise design of flotation reagents,as well as for the meticulous optimization of mineral surface interfaces,with the objective of enhancing flotation separation.
基金the Natural Science Basic Research Program of Shaanxi(Grant No.2024JC-ZDXM-01)supported by the Youth Innovation Team of Shaanxi Universities(Title:Service Performance Evaluation of Energetic Materials)。
文摘The ReaxFF can describe the properties of energetic materials(EMs)at equilibrium state,but does not work properly in simulating high-energy particle irradiation process because of its weak short-range interaction.In this paper,a modification was made for such a potential by connecting ZieglerBiersack-Littmark(ZBL)potential to ReaxFF-lg through comparing to Density Functional Theory(DFT)results to accurately describe short-range interactions.After modification,the newly fitted ReaxFF-lg/ZBL potential predicts better the equation of state for EMs In displacement cascade simulations,comparing to results from ab initio molecular dynamics(AIMD),ReaxFF-lg/ZBL presented the similar transferred energy from a primary knock-on atom to surrounding atoms,better than the original ReaxFF-lg potential.Further large-scale displacement cascade simulations indicated ReaxFF-lg/ZBL could be applied for cascade simulations with PKA energy from less than 1 keV to high energy(e.g.35 keV)cases,which is suitable for effectively simulating high-energy displacement cascades in EMs using molecular dynamics method.
基金supported by Key Science and Technology Innovation Team of Shaanxi Province(No.2022TD-33)National Natural Science Foundation of China(Grant Nos.21373161,21504067)。
文摘Traditional selection of combustion catalysis is time-consuming and labor-intensive.Theoretical calculation is expected to resolve this problem.The adsorption energy of HMX and O atoms on 13 metal oxides was calculated using DMol3,since HMX and O are key substances in decomposition process.And the relationship between the adsorption energy of HMX,O on metal oxides(TiO_(2),Al_(2)O_(3),PbO,CuO,Fe_(2)O_(3),Co_(3)O_(4),Bi_(2)O_(3),NiO)and experimental T30 values(time required for the decomposition depth of HMX to reach 30%)was depicted as volcano plot.Thus,the T30 values of other metal oxides was predicted based on their adsorption energy on volcano plot and validated by previous experimental data.Further,the adsorption energy of HMX on ZrO_(2)and MnO_(2)was predicted based on the linear relationship between surface energy and adsorption energy,and T30 values were estimated based on volcano plot.The apparent activation energy data of HMX/MgO,HMX/SnO_(2),HMX/ZrO_(2),and HMX/MnO_(2)obtained from DSC experiments are basically consistent with our predicted T30 values,indicating that it is feasible to predict the catalytic activity based on the adsorption calculation,and it is expected that these simple structural properties can predict adsorption energy to reduce the large quantities of computation and experiment cost.
基金Science and Technology Commission of Shanghai Municipality(21ZR1472900,22ZR1471600)。
文摘Platinum(Pt)-based noble metal catalysts(PGMs)are the most widely used commercial catalysts,but they have the problems of high cost,low reserves,and susceptibility to small-molecule toxicity.Transition metal oxides(TMOs)are regarded as potential substitutes for PGMs because of their stability in oxidizing environments and excellent catalytic performance.In this study,comprehensive investigation into the influence of elastic strains on the adsorption energies of carbon(C),hydrogen(H)and oxygen(O)on TMOs was conducted.Based on density functional theory(DFT)calculations,these effects in both tetragonal structures(PtO_(2),PdO_(2))and hexagonal structures(ZnO,CdO),along with their respective transition metals were systematically explored.It was identified that the optimal adsorption sites on metal oxides pinpointed the top of oxygen or the top of metal atom,while face-centered cubic(FCC)and hexagonal close-packed(HCP)holes were preferred for the transition metals.Furthermore,under the influence of elastic strains,the results demonstrated significant disparities in the adsorption energies of H and O between oxides and transition metals.Despite these differences,the effect of elastic strains on the adsorption energies of C,H and O on TMOs mirrored those on transition metals:adsorption energies increased under compressive strains,indicating weaker adsorption,and decreased under tension strains,indicating stronger adsorption.This behavior was rationalized based on the d-band model for adsorption atop a metallic atom or the p-band model for adsorption atop an oxygen atom.Consequently,elastic strains present a promising avenue for tailoring the catalytic properties of TMOs.
基金supported by National Natural Science Foundation of China(U23A20100)the Strategic Priority Research Program(A)of the Chinese Academy of Sciences(XDA0390404)+5 种基金ICC CAS SCJC-DT-2023-03,the Foundation of State Key Laboratory of Coal Conversion(J24-25-619)Youth Innovation Promotion Association CAS(2018209,2020179)Key R&D Program of Shanxi Province(202102090301008,202202090301013)the special fund for S&T Innovation Team of Shanxi Province(202204051001012)Project of International Cooperation and Exchange NSFC-RFBR(22011530069)Tianjin Science and Technology Plan Project(22YFYSHZ00290)。
文摘To enhance the separation selectivity of Mg-MOF-74 towards CO_(2) in a CO_(2)/N_(2) mixture,a series of Mg-MOF-74 and Ni_(x)/Mg_(1-x)-MOF-74 adsorbents were prepared by solvothermal synthesis in this paper.It was found that the adsorption capacity of Mg-MOF-74 for CO_(2) could be effectively increased by optimizing the amount of acetic acid.On this basis,the bimetal MOF-74 adsorbent was prepared by metal modification.The multi-component dynamic adsorption penetration analysis was utilized to examine the CO_(2) adsorption capacity and CO_(2)/N_(2) selectivity of the diverse adsorbent materials.The results showed that Ni0.11/Mg0.89-MOF-74 showed a CO_(2) adsorption capacity of 7.02 mmol/g under pure CO_(2) atmosphere and had a selectivity of 20.50 for CO_(2)/N_(2) under 15% CO_(2)/85%N_(2) conditions,which was 10.2% and 18.02% higher than that of Mg-MOF-74 respectively.Combining XPS,SEM and N_(2) adsorption-desorption characterization analysis,it was attributed to the effect of the more stable unsaturated metal sites Ni into the Mg-MOF-74 on the pore structure and the synergistic interaction between the two metals.Density Functional Theory(DFT)simulations revealed that the synergistic interaction between modulated the electrostatic potential strength and gradient of the material,which was more favorable for the adsorption of CO_(2) molecules with small diameters and large quadrupole moment.In addition,the Ni0.11/Mg0.89-MOF-74 showed commendable cyclic stability,underscoring its promising potential for practical applications.
基金Project(2022JJ30049)supported by the Natural Science Foundation of Hunan Province,China。
文摘The spin caloritronic properties of the Janus VSTe monolayer were investigated using density functional theory(DFT)and the non-equilibrium Green’s function(NEGF)method,implemented in the Atomistix Toolkit(ATK)package.Our study revealed significant spin-splitting within the Janus VSTe monolayer,which induced spin currents under a temperature gradient across the device.By applying a 1%tensile strain,the Janus VSTe monolayer exhibited a perfect thermal spin filtering effect(SFE),with the spin-up current nearly suppressed to zero.Both the unstrained and strained Janus VSTe monolayers demonstrated excellent spin caloritronic properties,with spin figures of merit of 10.915 and 8.432 at an average temperature of 100 K,respectively.Notably,these properties were found to be sensitive to temperature,performing optimally at lower temperatures.These results suggest a promising avenue for designing spin caloritronic devices aimed at efficient waste heat recovery.
基金Project supported by the Open Foundation of Guangxi Key Laboratory for Advanced Materials and Manufacturing Technology,China
文摘Electronic structures of monoclinic and hexagonal pyrrhotite were studied using density functional theory method,together with their flotation behavior. The main contribution of monoclinic pyrrhotite is mainly from Fe 3d, while that of hexagonal pyrrhotite is from Fe 3d, Fe 3p and S 3s. The hexagonal pyrrhotite is more reactive than monoclinic pyrrhotite because of large density of states near the Fermi level. The hexagonal pyrrhotite shows antiferromagnetism. S—Fe bonds mainly exist in monoclinic pyrrhotite as the covalent bonds, while hexagonal pyrrhotite has no covalency. The main contributions of higest occupied molecular orbital(HOMO) and lowest unoccupied molecular obital(LUMO) for monoclinic pyrrhotite come from S and Fe. The main contribution of HOMO for hexagonal pyrrhotite comes from Fe, while that of LUMO comes from S. The coefficient of Fe atom is much larger than that of S atom of HOMO for hexagonal pyrrhotite, which contributes to the adsorption of Ca OH+ on the surface of hexagonal pyrrhotite when there is lime. As a result, lime has the inhibitory effect on the floatation of hexagonal pyrrhotite and the coefficient of Fe is very close to that of S for monoclinic pyrrhotite. Therefore, the existence of S prevents the adsorption of Ca OH+on the surface of monoclinic pyrrhotite, which leads to less inhibitory effect on the flotation of monoclinic pyrrhotite.
基金Projects(51602352,51974373,51874358,51772333,61533020) supported by the National Natural Science Foundation of ChinaProject(2019JZZY020123) supported by the Major Scientific and Technological Innovation Projects of Shandong Province,China。
文摘Na-ion diffusion kinetics is a key factor that decided the charge/discharge rate of the electrode materials in Na-ion batteries.In this work,two extreme concentrations of NaMnO_(2) and Na_(2/3)Li_(1/6)Mn_(5/6)O_(2) are considered,namely,the vacancy migration of Na ions in the fully intercalated and the migration of Na ions in the fully de-intercalated.The Na-vacancy and Na^(+)distribution in NaMnO_(2) migrated along oxygen dumbbell hop(ODH)and tetrahedral site hop(TSH),and the migration energy barriers were 0.374 and 0.296 eV,respectively.In NaLi_(1/6)Mn_(5/6)O_(2),the inhomogeneity of Li doping leads to the narrowing of the interlayer spacing by 0.9%and the increase of the energy barrier by 53.8%.On the other hand,due to the alleviation of Jahn-Teller effect of neighboring Mn,the bonding strength of Mn-O was enhanced,so that the energy barrier of path 2-3 in Mn-L1 and Mn-L2 was the lowest,which was 0.234 and 0.424 eV,respectively.In Na_(1/6)Li_(1/6)Mn_(5/6)O_(2),the migration energy barriers of Na-L2 and Na-L3 are 1.233 and 0.779 eV,respectively,because Li+migrates from the transition(TM)layer to the alkali metal(AM)layer with Na^(+)migration,which requires additional energy.
文摘In this work,the Fukui functions of the two ~2P resonance states of Be,a ~2P resonance state of Mg~–,and a ~2D resonance state of Ca~– have been determined.The trajectories of these resonance states,in conjunction with the complex rotation of the Hamiltonian,were used to determine their wave functions.The electron densities,Fukui functions,and values of the hyper-radius<r^2>were computed from these wave functions.The Fukui functions have negative regions in the valence shell in addition to the inner shell regions,indicating screening effects of the outer temporary electron.Selected configuration interactions with up to quadruple excitations were used along the trajectories and for computing the final wave function.Based on this data,the densities,Fukui functions,and<r^2>were calculated.
基金support by FONDECYT(1140313)Financiamiento Basal para Centros Cientificos y Tecnoldgicos de Excelencia-FB0807project RC-130006 CILLIS,Chile
文摘Quantitative correlation of several theoretical electrophilicity measures over different families of organic compounds are examined relative to the experimental values of Mayr et al.Notably,the ability to predict these values accurately will help to elucidate the reactivity and selectivity trends observed in charge-transfer reactions.A crucial advantage of this theoretical approach is that itprovides this information without the need of experiments,which are often demanding and time-consuming.Here,two different types of electrophilicity measures were analyzed.First,models derived from conceptual density functional theory(c-DFT),including Parr's original proposal and further generalizations of this index,are investigated.For instance,the approaches of Gázquez et al.and Chamorro et al.are considered,whereby it is possible to distinguish between processes in which a molecule gains or loses electrons.Further,we also explored two novel electrophilicity definitions.On one hand,the potential of environmental perturbations to affect electron incorporation into a system is analyzed in terms of recent developments in c-DFT.These studies highlight the importance of considering the molecular surroundings when a consistent description of chemical reactivity is needed.On the other hand,we test a new definition of electrophilicity that is free from inconsistencies(so-called thermodynamic electrophilicity).This approach is based on Parr's pioneering insights,though it corrects issues present in the standard working expression for the calculation of electrophilicity.Additionally,we use machine-learning tools(i.e.,symbolic regression)to identify the models that best fit the experimental values.In this way,the best possible description of the electrophilicity values in terms of different electronic structure quantities is obtained.Overall,this straightforward approach enables one to obtain good correlations between the theoretical and experimental quantities by using the simple,yet powerful,interpretative advantage of c-DFT methods.In general,we observed that the correlations found at the HF/6-31 G(d)level of theory are of semi-quantitative value.To obtain more accurate results,we showed that working with families of compounds with similar functional groups is indispensable.
基金Project(07JJ3102)supported by the Natural Science Foundation of Hunan Province,ChinaProject(k0902132-11)supported by the Changsha Municipal Science and Technology,China
文摘The equilibrium lattice parameters, electronic structure, bulk modulus, Debye temperature, heat capacity and Gibbs energy of TiB and TiB2 were investigated using the pseudopotential plane-wave method based on density functional theory (DFT) and the improved quasi-harmonic Debye method. The results show that the total density of states (DOS) of TiB2 is mainly provided by the orbit hybridization of Ti-3d and B-2p states, and the total DOS of TiB is mainly provided by the hybrids bond of Ti-3d and B-2p below the Fermi level and Ti—Ti bond up to the Fermi level. The Ti—B hybrid bond in TiB2 is stronger than that in TiB. Finally, the enthalpy of formation at 0 K, heat capacity and Gibbs free energy of formation at various temperatures were determined. The calculated results are in excellent agreement with the available experimental data.
文摘The molecular structure of cyclohexanone was calculated by the B3LYP density functional model with 6-31G(d,p)and 6-311++G(d,p)basis set by Gaussian program.The results from natural bond orbital(NBO)analysis have been analyzed in terms of the hybridization of atoms and the electronic structure of the title molecule.The electron density based local reactivity descriptors such as Fukui functions were calculated.The dipole moment(μ)and polarizability(α),anisotropy polarizability(Δα)and first order hyperpolarizability(βtot)of the molecule have been reported.Thermodynamic properties of the title compound were calculated at different temperatures.
