The structural and electronic properties of TiC（110） surfaces are calculated using the first-principles total-energy plane-wave pseudopotential method based on density functional theory. The calculated results of st...The structural and electronic properties of TiC（110） surfaces are calculated using the first-principles total-energy plane-wave pseudopotential method based on density functional theory. The calculated results of structural relaxation and surface energy for TiC（110） slab indicate that slab with 7 layers shows bulk-like characteristic interiors, and the changes of slab occur on the outmost three layers, which shows that the relaxation only influences the top three layers. Meanwhile, the strong Ti—C covalent bonding can be found in the distribution of charge density on the （100） plane. The interlayer Ti—C chemical bonds are reinforced and the outermost interlayer distance is reduced as a result of the charge depletion in the vacuum and the charge accumulations in the interlayer region between the first and second layers. The surface energy of TiC（110） is calculated to be 3.53 J/m2.展开更多
The structural and electronic properties of bulk and (001) plane of TiC were investigated by the first-principles total-energy pseudopotential method based on density functional theory.The calculated bulk properties i...The structural and electronic properties of bulk and (001) plane of TiC were investigated by the first-principles total-energy pseudopotential method based on density functional theory.The calculated bulk properties indicate that bonding nature in TiC is a combination of ionicity,covalency and metallicity,in which the Ti-C covalent bonding is the predominate one.The calculated results of structural relaxation and surface energy for TiC(001) slab indicate that slab with 7 layers shows bulk-like characteristic interiors,and the changes of slab occur on the outmost three layers,which shows that the relaxation only influences the top three layers.Meanwhile,the strong Ti-C covalent bonding can be found in the distribution of charge density on the (110) and (001) planes.Ti-C covalent bonding is enhanced by the charge depletion and accumulation in the vacuum and the interlayer region between top two atomic layers.展开更多
For a low surface barrier, the energy band, barrier height and width of the space charge region at the surface of relatively large grains of ZnO are presented analytically on condition that the electron distribution o...For a low surface barrier, the energy band, barrier height and width of the space charge region at the surface of relatively large grains of ZnO are presented analytically on condition that the electron distribution obeys the Boltzmann statistics. It is shown that the temperature in the space charge distribution factor has an important effect on the energy band, barrier height and width of the space charge region. The depletion approximation is a model in which the temperature in the space charge distribution factor is zero. Our results are better than the depletion approximation.展开更多
Surface charge distribution of particles is the fundamental problem for adsorption and desorption between sediment and contaminant. In this paper, we take quartz sand for example to measure its micro-morphology and su...Surface charge distribution of particles is the fundamental problem for adsorption and desorption between sediment and contaminant. In this paper, we take quartz sand for example to measure its micro-morphology and surface charge distribution using the phase mode of the electrical force microscope. Then the statistical relation of micro-morphology and surface charge distribution is obtained. Results show that quartz sand possesses complex surface morphology, which has great impact on the charge distribution. Positive and negative charges mostly concentrate on the saddle, convex and concave parts of the surface, while distribute less in the groove, ridge and flat parts. This experiment provides a new method for understanding the process of flocculation in coastal and estuarine zone.展开更多
Ion specificity of Na＋ and C1- ions for NaCI solution confined in silicon nanochannels is investigated with molecular dynamics （MD） simulations. The MD simulation results demonstrate that ion specificity for Na＋ a...Ion specificity of Na＋ and C1- ions for NaCI solution confined in silicon nanochannels is investigated with molecular dynamics （MD） simulations. The MD simulation results demonstrate that ion specificity for Na＋ and C1- ions exhibits clearly in na- nochannels with high surface charge density. The two types of ions show different density distributions perpendicular to the channel surface due to the ion specificity when they act as countefions near negatively and positively charged surfaces, respec- tively. Both the two counterion distributions cannot be predicted by Poisson-Boltzmann equation within 0.75 nm near the sur- face. In addition, the ion specificity is also demonstrated through affecting the water density distributions. In the nanochannel with negatively charged surfaces, the presence of the Na＋ ions reduces the number of water peaks in water density distribution profile. In comparison, when the C1- ions act as counterions near positively charged surfaces, they do not affect the number of the water peaks. Besides the influence on the water density distribution, ion specificity also exhibits through affecting the wa- ter molecule orientation in the adsorbed layer. It is found that C1- ions make the water molecules in the adsorbed layer align more orderly than Na~ ions do when the two types of ions act as the counterions near the positively and negatively charged surfaces with the same surface charge density.展开更多
基金Project (200902554) supported by National Post-doctor Foundation, ChinaProject (200802015) supported by the Post-Doctor Foundation of Shandong Province, China
文摘The structural and electronic properties of TiC（110） surfaces are calculated using the first-principles total-energy plane-wave pseudopotential method based on density functional theory. The calculated results of structural relaxation and surface energy for TiC（110） slab indicate that slab with 7 layers shows bulk-like characteristic interiors, and the changes of slab occur on the outmost three layers, which shows that the relaxation only influences the top three layers. Meanwhile, the strong Ti—C covalent bonding can be found in the distribution of charge density on the （100） plane. The interlayer Ti—C chemical bonds are reinforced and the outermost interlayer distance is reduced as a result of the charge depletion in the vacuum and the charge accumulations in the interlayer region between the first and second layers. The surface energy of TiC（110） is calculated to be 3.53 J/m2.
基金Project(200802015) supported by Post-doctoral Foundation of Shandong Province,ChinaProject(50625101) supported by the National Natural Science Foundation for Distinguished Young Scholars of China
文摘The structural and electronic properties of bulk and (001) plane of TiC were investigated by the first-principles total-energy pseudopotential method based on density functional theory.The calculated bulk properties indicate that bonding nature in TiC is a combination of ionicity,covalency and metallicity,in which the Ti-C covalent bonding is the predominate one.The calculated results of structural relaxation and surface energy for TiC(001) slab indicate that slab with 7 layers shows bulk-like characteristic interiors,and the changes of slab occur on the outmost three layers,which shows that the relaxation only influences the top three layers.Meanwhile,the strong Ti-C covalent bonding can be found in the distribution of charge density on the (110) and (001) planes.Ti-C covalent bonding is enhanced by the charge depletion and accumulation in the vacuum and the interlayer region between top two atomic layers.
文摘For a low surface barrier, the energy band, barrier height and width of the space charge region at the surface of relatively large grains of ZnO are presented analytically on condition that the electron distribution obeys the Boltzmann statistics. It is shown that the temperature in the space charge distribution factor has an important effect on the energy band, barrier height and width of the space charge region. The depletion approximation is a model in which the temperature in the space charge distribution factor is zero. Our results are better than the depletion approximation.
基金supported by the National Natural Science Foundation of China (Grant No. 50909095)Chinese Universities Scientific Fund (Grant No. 2011JS131)
文摘Surface charge distribution of particles is the fundamental problem for adsorption and desorption between sediment and contaminant. In this paper, we take quartz sand for example to measure its micro-morphology and surface charge distribution using the phase mode of the electrical force microscope. Then the statistical relation of micro-morphology and surface charge distribution is obtained. Results show that quartz sand possesses complex surface morphology, which has great impact on the charge distribution. Positive and negative charges mostly concentrate on the saddle, convex and concave parts of the surface, while distribute less in the groove, ridge and flat parts. This experiment provides a new method for understanding the process of flocculation in coastal and estuarine zone.
基金supported by the National Basic Research Program of Chi-na(Grant Nos.2011CB707601,2011CB707605)the National Natural Science Foundation of China(Grant No.50925519)+3 种基金the Research Funding for the Doctor Program from China Educational Ministry(Grant No.20100092110051)the Innovative Project for Graduate Students of Jiangsu Province(Grant No.CXZZ13_0087)the Scientific Research Founda-tion of Graduate School of Southeast University(Grant No.YBJJ1322)The calculations were performed on Tianhe-1A at National Supercomputing Center in Tianjin,China
文摘Ion specificity of Na＋ and C1- ions for NaCI solution confined in silicon nanochannels is investigated with molecular dynamics （MD） simulations. The MD simulation results demonstrate that ion specificity for Na＋ and C1- ions exhibits clearly in na- nochannels with high surface charge density. The two types of ions show different density distributions perpendicular to the channel surface due to the ion specificity when they act as countefions near negatively and positively charged surfaces, respec- tively. Both the two counterion distributions cannot be predicted by Poisson-Boltzmann equation within 0.75 nm near the sur- face. In addition, the ion specificity is also demonstrated through affecting the water density distributions. In the nanochannel with negatively charged surfaces, the presence of the Na＋ ions reduces the number of water peaks in water density distribution profile. In comparison, when the C1- ions act as counterions near positively charged surfaces, they do not affect the number of the water peaks. Besides the influence on the water density distribution, ion specificity also exhibits through affecting the wa- ter molecule orientation in the adsorbed layer. It is found that C1- ions make the water molecules in the adsorbed layer align more orderly than Na~ ions do when the two types of ions act as the counterions near the positively and negatively charged surfaces with the same surface charge density.
