First-principles evolutionary calculation was performed to search for all probable stable Ga–Te compounds at extreme pressure. In addition to the well-known structures of P6_3/mmc and Fm-3 m Ga Te and I4/m Ga_2 Te_5,...First-principles evolutionary calculation was performed to search for all probable stable Ga–Te compounds at extreme pressure. In addition to the well-known structures of P6_3/mmc and Fm-3 m Ga Te and I4/m Ga_2 Te_5, several new structures were uncovered at high pressure, namely, orthorhombic I4/mmm GaTe_2 and monoclinic C2/m Ga Te_3, and all the Ga–Te structures stabilize up to a maximum pressure of 80 GPa. The calculation of the electronic energy band indicated that the high-pressure phases of the Ga–Te system are metallic, whereas the low-pressure phases are semiconductors. The electronic localization functions(ELFs) of the Ga–Te system were also calculated to explore the bond characteristics. The results showed that a covalent bond is formed at low pressure, however, this bond disappears at high pressure, and an ionic bond is formed at extreme pressure.展开更多
The variational and diffusion Monte Carlo approaches are used to study the ground-state properties of a hydrogen molecular ion in a spheroidal box. In this work, we successfully treat the zero-point motion of protons ...The variational and diffusion Monte Carlo approaches are used to study the ground-state properties of a hydrogen molecular ion in a spheroidal box. In this work, we successfully treat the zero-point motion of protons in the same formalism with as of electrons and avoid the Born–Oppenheimer approximation in density function theory. The study shows that the total energy increases with the decrease in volume, and that the distance between protons decreases as the pressure increases.Considering the motion of protons, the kinetic energy of the electron is higher than that of the fixed model under the same conditions and increases by 5%. The kinetic energy of the proton is found to be small under high pressure, which is only a fraction of the kinetic energy of the electron.展开更多
As the previously proposed structures of C2/m and C2/c possess similar enthalpies and x-ray diffraction patterns, the space group of fluorine at ambient pressure is in controversy. We successfully obtain its thermodyn...As the previously proposed structures of C2/m and C2/c possess similar enthalpies and x-ray diffraction patterns, the space group of fluorine at ambient pressure is in controversy. We successfully obtain its thermodynamically stable lowpressure phase, which shares the same structure as the earlier known C2/c. Further investigations on phonon spectra reveal the instability of the C2/m structure with imaginary frequency in the Brillouin zone and confirm the dynamically stable property of the C2/c structure at the same time. Compressing fluorine up to 8 GPa, the C2/c phase is found to undergo a phase transition to a new structure with a space group of Cmca. Electronic energy band structures indicate the insulating feature of C2/c and Cmca with no bands across the Fermi level. The infrared（IR） and Raman spectra of C2/c and Cmca at selected pressures are calculated to provide useful information to future experiments.展开更多
We conduct extensive research into the structures of Be_(x)Zn_(1-x)OO ternary alloys in a pressure range of 0-60GPa,using the ab initio total energy evolutionary algorithm and total energy calculations,finding several...We conduct extensive research into the structures of Be_(x)Zn_(1-x)OO ternary alloys in a pressure range of 0-60GPa,using the ab initio total energy evolutionary algorithm and total energy calculations,finding several metastable structures.Our pressure-composition phase diagram is constructed using the enthalpy results.In addition,we calculate the electronic structures of the Be_(x)Zn_(1-x)OO structures and investigate the bandgap values at varying pressures and Be content.The calculated results show that the bandgap of the Be_(x)Zn_(1-x)OO ternary alloys increases with an increase in Be content at the same pressure.Moreover,the bandgap of the Be_(x)Zn_(1-x)OO ternary alloys increases with the increasing pressure with fixed Be content.At the same Be content,the formation enthalpy of the Be_(x)Zn_(1-x)OO ternary alloys first decreases,then increases with the increasing pressure.展开更多
基金Project supported by the National Key R&D Program of China(Grant Nos.2018YFA0305900 and 2016YFB0201204)the National Natural Science Foundation of China(Grant Nos.51632002,51572108,11574109,91745203,and 11634004)+1 种基金Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT 15R23)National Fund for Fostering Talents of Basic Science,China(Grant No.J1103202)
文摘First-principles evolutionary calculation was performed to search for all probable stable Ga–Te compounds at extreme pressure. In addition to the well-known structures of P6_3/mmc and Fm-3 m Ga Te and I4/m Ga_2 Te_5, several new structures were uncovered at high pressure, namely, orthorhombic I4/mmm GaTe_2 and monoclinic C2/m Ga Te_3, and all the Ga–Te structures stabilize up to a maximum pressure of 80 GPa. The calculation of the electronic energy band indicated that the high-pressure phases of the Ga–Te system are metallic, whereas the low-pressure phases are semiconductors. The electronic localization functions(ELFs) of the Ga–Te system were also calculated to explore the bond characteristics. The results showed that a covalent bond is formed at low pressure, however, this bond disappears at high pressure, and an ionic bond is formed at extreme pressure.
基金Project supported by the National Key R&D Program of China(Grant No.2018YFA0305900)the National Natural Science Foundation of China(Grant Nos.51632002,51572108,91745203,11634004,11174102,and 1174121)+2 种基金the National Key Research and Development Program of China(Grant No.2016YFB0201204)the Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT 15R23)the National Fund for Fostering Talents of Basic Science,China(Grant No.J1103202)
文摘The variational and diffusion Monte Carlo approaches are used to study the ground-state properties of a hydrogen molecular ion in a spheroidal box. In this work, we successfully treat the zero-point motion of protons in the same formalism with as of electrons and avoid the Born–Oppenheimer approximation in density function theory. The study shows that the total energy increases with the decrease in volume, and that the distance between protons decreases as the pressure increases.Considering the motion of protons, the kinetic energy of the electron is higher than that of the fixed model under the same conditions and increases by 5%. The kinetic energy of the proton is found to be small under high pressure, which is only a fraction of the kinetic energy of the electron.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51632002,51572108,11634004,and 11174102)Program for Changjiang Scholars and Innovative Research Team in University,China(Grant No.IRT 15R23)+1 种基金the National Fund for Fostering Talents of Basic Science,China(Grant No.J1103202)the Development Program of Science and Technology of Jilin Province,China(Grant No.20150312002ZG)
文摘As the previously proposed structures of C2/m and C2/c possess similar enthalpies and x-ray diffraction patterns, the space group of fluorine at ambient pressure is in controversy. We successfully obtain its thermodynamically stable lowpressure phase, which shares the same structure as the earlier known C2/c. Further investigations on phonon spectra reveal the instability of the C2/m structure with imaginary frequency in the Brillouin zone and confirm the dynamically stable property of the C2/c structure at the same time. Compressing fluorine up to 8 GPa, the C2/c phase is found to undergo a phase transition to a new structure with a space group of Cmca. Electronic energy band structures indicate the insulating feature of C2/c and Cmca with no bands across the Fermi level. The infrared（IR） and Raman spectra of C2/c and Cmca at selected pressures are calculated to provide useful information to future experiments.
基金Supported by the National Key Research and Development Program of China(Grant Nos.2016YFB0201204,2018YFA0703404,and 2017YFA0403704)the National Natural Science Foundation of China(Grant Nos.11574109 and 91745203)the Program for Changjiang Scholars and Innovative Research Team in Universities(Grant No.IRT_15R23).
文摘We conduct extensive research into the structures of Be_(x)Zn_(1-x)OO ternary alloys in a pressure range of 0-60GPa,using the ab initio total energy evolutionary algorithm and total energy calculations,finding several metastable structures.Our pressure-composition phase diagram is constructed using the enthalpy results.In addition,we calculate the electronic structures of the Be_(x)Zn_(1-x)OO structures and investigate the bandgap values at varying pressures and Be content.The calculated results show that the bandgap of the Be_(x)Zn_(1-x)OO ternary alloys increases with an increase in Be content at the same pressure.Moreover,the bandgap of the Be_(x)Zn_(1-x)OO ternary alloys increases with the increasing pressure with fixed Be content.At the same Be content,the formation enthalpy of the Be_(x)Zn_(1-x)OO ternary alloys first decreases,then increases with the increasing pressure.
