The reflection of light ions, such as H+,3He+ and 4He+, with energies of 0.1- 10 keV, from Cu and Ni surface has been studied by Monte Carlo simulation and transport theory. The Monte Carlo simulation gives the detail...The reflection of light ions, such as H+,3He+ and 4He+, with energies of 0.1- 10 keV, from Cu and Ni surface has been studied by Monte Carlo simulation and transport theory. The Monte Carlo simulation gives the detail energy spectra for the reflected particles and their angular distribution for different incident angles. It shows that the reflected particle energy spectra can be approximately described by an analytical formula for the whole energy range, all the incident angles and different ion- target combination studied here. The reflected particle energy vs its average reflection angle to the surface normal can almost be expressed by a universal curve for all cases studied here. The reflection energy spectra are used for the calculation of the reflection coefficient by transport theory including the realistic surface correction. The present work is compared with both experimental measurement and other simulation codes.展开更多
Transmission energy spectra of 530 keV H^(+) ion penetrating 140μm thick seed coat of maize and fruit peel of grape with thickness of 100μm were measured.The result indicates that these thick biological targets,as s...Transmission energy spectra of 530 keV H^(+) ion penetrating 140μm thick seed coat of maize and fruit peel of grape with thickness of 100μm were measured.The result indicates that these thick biological targets,as seen by the penetrating ions,are inhomogeneous,and there are open“channel like”paths along which the incidentions can transmit the targets easily.While most of the incident ions are stopped in the targets,some of the transmitting ions only lose a small fraction of their initial incident energy.The transmission energy spectra show a pure electronic stopping feature.Transmission electron microscope(TEM)micrographes taken from the samples of seed coat of maize and fruit peel of tomato with thickness of 60μm indicate that 150keV electron beam from the TEM can penetrate the thick samples to give very good images with clear contrasts.展开更多
The hydrogen storage capacity of （5, 5） single-walled carbon nanotubes （SWNTs） decorated chemically with benzene moieties is studied by using molecular dynamics simulations （MDSs） and density functional theory ...The hydrogen storage capacity of （5, 5） single-walled carbon nanotubes （SWNTs） decorated chemically with benzene moieties is studied by using molecular dynamics simulations （MDSs） and density functional theory （DFT） calculations. It is found that benzene molecules colliding on （5, 5） SWNTs at incident energy of 50eV form very stable configurations of benzene moiety adsorption on the wall of SWNTs. The MDSs indicate that when the benzene moiety decorated （5, 5） SWNTs and a pristine （5, 5） SWNT are put in a box in which hydrogen molecules are filled to a pressure of ～26 atm, the hydrogen storage capacity of the benzene moiety decorated （5, 5） SWNT is about 4.7wt.% and that of the pristine （5, 5） SWNT is nearly 3.9wt.%.展开更多
Electronic stopping powers for 0. 05-10 MeV protons in a group of organic materials are systematically calculated. The calculations are based on Ashley＇s dielectric model, and an evaluation approach of optical energy...Electronic stopping powers for 0. 05-10 MeV protons in a group of organic materials are systematically calculated. The calculations are based on Ashley＇s dielectric model, and an evaluation approach of optical energy loss function is incorporated into Ashley＇s model because no experimental optical data are available for most of the organic materials under consideration. The Barkas-effect correction and Bloch correction are included. The proton stopping powers for the considered organic materials except for mylar in the energy range from 0.05 to 10 MeV are presented for the first time. The results may be useful for studies of various radiation effects in these materials and for space research.展开更多
We perform the calculations on geometric and electronic structures of Si-doped heterofullerene C5oSi10 and its derivatives, a C40Si20-C40Si20 dimer and a C40Si20-based nanowire by using density-functional theory, The ...We perform the calculations on geometric and electronic structures of Si-doped heterofullerene C5oSi10 and its derivatives, a C40Si20-C40Si20 dimer and a C40Si20-based nanowire by using density-functional theory, The optimized configuration of the C40Si20-based nanowire exhibits a regular dumbbell-shaped chain nanostructure. The electronic structure calculations indicate that the HOMO-LUMO gaps of the heterofullerene-based materials can be greatly modified by substitutionally doping with Si atoms and show a decreasing trend with increase cluster size. Unlike the band structures of the conventional wide band gap silicon carbide nanomaterials, the C40Si20- based nanowire has a very narrow direct band gap of 0.087eV.展开更多
A molecular dynamics simulation method is used to study the growth of narrow single-wall carbon nanotubes.It is found that the growth temperature and the species of small carbon clusters in the feedstock are important...A molecular dynamics simulation method is used to study the growth of narrow single-wall carbon nanotubes.It is found that the growth temperature and the species of small carbon clusters in the feedstock are important for the quality of the nanotubes grown.There is a temperature range of 1000-1500 K in which the narrow armchair single-wall carbon nanotubes can grow rapidly via adduction of C2 dimers,even without the existence of catalysts.The narrow zigzag tubes cannot keep open-ended growth.If the feedstock consists of various species of carbon clusters,the tubes cannot keep open-ended growth.At higher temperatures,the narrow nanotubes close rapidly in the noncatalytic environment,and the products grown are fullerene-like capsules.展开更多
Experimental evidence of abnormally deep penetration in some botanical targets by low-energy ion beams is presented.The energy spectra of 818 keV He^(+)ions penetrating a 70μm thick seed coat of maize,fruit peel of g...Experimental evidence of abnormally deep penetration in some botanical targets by low-energy ion beams is presented.The energy spectra of 818 keV He^(+)ions penetrating a 70μm thick seed coat of maize,fruit peel of grape and of tomato all have a common feature.The leading edges of these broad spectra indicate that some of the penetrating ions pass through the thick targets easily and only lose a small fraction of their initial incident energy.Rutherford backscattering spectrometry and electron microprobe measurements are used to determine the argon concentration in multilayer samples of the seed coat of maize implanted by 200 keV Ar^(+)ions.The results show that about 10%of the Ar^(+)ions can penetrate deeper than~100μm in these samples.展开更多
The depth profile of Br in ^(79)Br^(+) ion implanted lead-tin-telluride,Pb_(1-x)Sn_(x),was obtained by secondary ion mass spectrometry(SIMS).The SIMS profile has been compared with that obtained by our theoretical cal...The depth profile of Br in ^(79)Br^(+) ion implanted lead-tin-telluride,Pb_(1-x)Sn_(x),was obtained by secondary ion mass spectrometry(SIMS).The SIMS profile has been compared with that obtained by our theoretical calculation,in which a more realistic interatomic potential and reasonable electronic stopping power were used.The SIMS result agrees well with the theoretical calculation.展开更多
We theoretically show that H atoms can be chemically adsorbed onto the surface of the Si-C heterofullerene- based nanotubes. The adsorbing energy of the H atom on Si-C heterofullerene-based nanotubes is in the range o...We theoretically show that H atoms can be chemically adsorbed onto the surface of the Si-C heterofullerene- based nanotubes. The adsorbing energy of the H atom on Si-C heterofullerene-based nanotubes is in the range of 4.28-5.66 eV without any barrier for the H atom to approach to the Si-C heterofullerene-based nanotubes. The band-gap of Si-C heterofullerene-based nanotubes can be dramatically modified by introducing dopant states, i.e., there is a transition from semiconductor to conductor of the Si-C heterofullerene-based nanotubes induced by the adsorption of the H atom. These results actually open a way to tune electronic properties of heterofullerene-based nanotubes and thus may propose an efficient pathway for band structure engineering.展开更多
Inelastic mean free paths （MFPs） of 0.05-10 MeV protons in a group of 10 organic compounds are systematically calculated. The calculations are based on the method newly derived from the Ashley optical-data model and...Inelastic mean free paths （MFPs） of 0.05-10 MeV protons in a group of 10 organic compounds are systematically calculated. The calculations are based on the method newly derived from the Ashley optical-data model and from the higher-order correction terms in stopping power calculations. Especially, in this method the new and empirical Bloch correction for the inelastic MFP is given. An evaluation for the optical energy loss function is incorporated into the present calculations because of the lack of available experimental optical data for the considered organic compounds expect for kapton. The proton inelastic MFPs for these 10 organic compounds in the energy range from 0.05 to 10 MeV are presented here for the first time, and the combination of these inelastic MFP data and our previous data of stopping power calculation for these bioorganic compounds may form a useful database for Monte Carlo track-structure studies of various radiation effects on these materials.展开更多
基金The Project Supported by the National Natural Science Foundation of China
文摘The reflection of light ions, such as H+,3He+ and 4He+, with energies of 0.1- 10 keV, from Cu and Ni surface has been studied by Monte Carlo simulation and transport theory. The Monte Carlo simulation gives the detail energy spectra for the reflected particles and their angular distribution for different incident angles. It shows that the reflected particle energy spectra can be approximately described by an analytical formula for the whole energy range, all the incident angles and different ion- target combination studied here. The reflected particle energy vs its average reflection angle to the surface normal can almost be expressed by a universal curve for all cases studied here. The reflection energy spectra are used for the calculation of the reflection coefficient by transport theory including the realistic surface correction. The present work is compared with both experimental measurement and other simulation codes.
基金Supported by the National Natural Science Foundation of China under Grant No.19890300in part by the Foundation for Ph.D.Education Programs from the National Education Commission of China under Grant No.96042208.
文摘Transmission energy spectra of 530 keV H^(+) ion penetrating 140μm thick seed coat of maize and fruit peel of grape with thickness of 100μm were measured.The result indicates that these thick biological targets,as seen by the penetrating ions,are inhomogeneous,and there are open“channel like”paths along which the incidentions can transmit the targets easily.While most of the incident ions are stopped in the targets,some of the transmitting ions only lose a small fraction of their initial incident energy.The transmission energy spectra show a pure electronic stopping feature.Transmission electron microscope(TEM)micrographes taken from the samples of seed coat of maize and fruit peel of tomato with thickness of 60μm indicate that 150keV electron beam from the TEM can penetrate the thick samples to give very good images with clear contrasts.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10374059 and 50402017, and the National Basic Research Programme of China under Grant No 2005CB623602.
文摘The hydrogen storage capacity of （5, 5） single-walled carbon nanotubes （SWNTs） decorated chemically with benzene moieties is studied by using molecular dynamics simulations （MDSs） and density functional theory （DFT） calculations. It is found that benzene molecules colliding on （5, 5） SWNTs at incident energy of 50eV form very stable configurations of benzene moiety adsorption on the wall of SWNTs. The MDSs indicate that when the benzene moiety decorated （5, 5） SWNTs and a pristine （5, 5） SWNT are put in a box in which hydrogen molecules are filled to a pressure of ～26 atm, the hydrogen storage capacity of the benzene moiety decorated （5, 5） SWNT is about 4.7wt.% and that of the pristine （5, 5） SWNT is nearly 3.9wt.%.
基金Supported by the Specialized Research Fund for the Doctoral Programme of Higher Education of China under Grant No 20050422038, and the Natural Science Foundation of Shandong Province under Grant No Y2005D02.
文摘Electronic stopping powers for 0. 05-10 MeV protons in a group of organic materials are systematically calculated. The calculations are based on Ashley＇s dielectric model, and an evaluation approach of optical energy loss function is incorporated into Ashley＇s model because no experimental optical data are available for most of the organic materials under consideration. The Barkas-effect correction and Bloch correction are included. The proton stopping powers for the considered organic materials except for mylar in the energy range from 0.05 to 10 MeV are presented for the first time. The results may be useful for studies of various radiation effects in these materials and for space research.
基金Supported by the National Natural Science Foundation of China under Grant Nos 10675075, 50402017 and 10604039, the National Basic Research Programme of China under Grant No 2005CB623602, the Program for New Century Excellent Talents in University of China, the Outstanding Youth Scientist Research Foundation of Shandong Province, and the Foundation of Ministry of Education of China under Grant Nos 2006BS04012 and 20050422006, and the Excellent Middle-Aged and Young Scientist Award Foundation of Shandong Province under Grant No 2004BS5007.
文摘We perform the calculations on geometric and electronic structures of Si-doped heterofullerene C5oSi10 and its derivatives, a C40Si20-C40Si20 dimer and a C40Si20-based nanowire by using density-functional theory, The optimized configuration of the C40Si20-based nanowire exhibits a regular dumbbell-shaped chain nanostructure. The electronic structure calculations indicate that the HOMO-LUMO gaps of the heterofullerene-based materials can be greatly modified by substitutionally doping with Si atoms and show a decreasing trend with increase cluster size. Unlike the band structures of the conventional wide band gap silicon carbide nanomaterials, the C40Si20- based nanowire has a very narrow direct band gap of 0.087eV.
基金Supported by the National Natural Science Foundation of China under Grant No.59972017the Education Ministry of China.
文摘A molecular dynamics simulation method is used to study the growth of narrow single-wall carbon nanotubes.It is found that the growth temperature and the species of small carbon clusters in the feedstock are important for the quality of the nanotubes grown.There is a temperature range of 1000-1500 K in which the narrow armchair single-wall carbon nanotubes can grow rapidly via adduction of C2 dimers,even without the existence of catalysts.The narrow zigzag tubes cannot keep open-ended growth.If the feedstock consists of various species of carbon clusters,the tubes cannot keep open-ended growth.At higher temperatures,the narrow nanotubes close rapidly in the noncatalytic environment,and the products grown are fullerene-like capsules.
基金Supported by the National Natural Science Foundation of China under Grant No.19890300by the Foundation for Doctoral Education Programs from the Education Ministry of China under Grant No.96042208.
文摘Experimental evidence of abnormally deep penetration in some botanical targets by low-energy ion beams is presented.The energy spectra of 818 keV He^(+)ions penetrating a 70μm thick seed coat of maize,fruit peel of grape and of tomato all have a common feature.The leading edges of these broad spectra indicate that some of the penetrating ions pass through the thick targets easily and only lose a small fraction of their initial incident energy.Rutherford backscattering spectrometry and electron microprobe measurements are used to determine the argon concentration in multilayer samples of the seed coat of maize implanted by 200 keV Ar^(+)ions.The results show that about 10%of the Ar^(+)ions can penetrate deeper than~100μm in these samples.
基金Projects supported by the Science Fund of the Chinese Academy of Sciences。
文摘The depth profile of Br in ^(79)Br^(+) ion implanted lead-tin-telluride,Pb_(1-x)Sn_(x),was obtained by secondary ion mass spectrometry(SIMS).The SIMS profile has been compared with that obtained by our theoretical calculation,in which a more realistic interatomic potential and reasonable electronic stopping power were used.The SIMS result agrees well with the theoretical calculation.
基金Supported by the National Natural Science Foundation of China under Grant Nos 50525206 and U0734004, and the Ministry of Education （106126）, the Postdoctoral Science Foundation of China under Grant No 20090450903, and Shanghai Supercomputer Center.
文摘We theoretically show that H atoms can be chemically adsorbed onto the surface of the Si-C heterofullerene- based nanotubes. The adsorbing energy of the H atom on Si-C heterofullerene-based nanotubes is in the range of 4.28-5.66 eV without any barrier for the H atom to approach to the Si-C heterofullerene-based nanotubes. The band-gap of Si-C heterofullerene-based nanotubes can be dramatically modified by introducing dopant states, i.e., there is a transition from semiconductor to conductor of the Si-C heterofullerene-based nanotubes induced by the adsorption of the H atom. These results actually open a way to tune electronic properties of heterofullerene-based nanotubes and thus may propose an efficient pathway for band structure engineering.
基金Supported by the Specialized Research Found for the Doctoral Program of Higher Education of China under Grant No 20050422038, and the Natural Science Foundation of Shandong Province under Grant No ZR2009DZ006.
文摘Inelastic mean free paths （MFPs） of 0.05-10 MeV protons in a group of 10 organic compounds are systematically calculated. The calculations are based on the method newly derived from the Ashley optical-data model and from the higher-order correction terms in stopping power calculations. Especially, in this method the new and empirical Bloch correction for the inelastic MFP is given. An evaluation for the optical energy loss function is incorporated into the present calculations because of the lack of available experimental optical data for the considered organic compounds expect for kapton. The proton inelastic MFPs for these 10 organic compounds in the energy range from 0.05 to 10 MeV are presented here for the first time, and the combination of these inelastic MFP data and our previous data of stopping power calculation for these bioorganic compounds may form a useful database for Monte Carlo track-structure studies of various radiation effects on these materials.
