Atomic structure of Si nanowires on Ag(110): A density-functional theory study

We have systematically investigated the adsorption of Si on the Ag(110) surface employing density-functional theory. Various adsorption geometries have been considered for Si coverages up to 2.0 monolayers. Our results show that the Si-Ag bonds are slightly more favorable than the Si-Si bonds at low Si coverage and an attractive interaction between the Si adatoms is also identified. From the calculated results, we identify the most possible atomic structures of Si nanowires on the Ag(110) surface and propose a reasonable mechanism for the growth of Si nanowires on the Ag(110) surface

First-principles study of the structure of methanethiolate on Ag(111)

We have systematically investigated the adsorption of methanethiolate (CH3S) on the Ag(111) surface employing density-functional theory. Various adsorption geometries have been considered and the energetically most favorable structure of CH3S/Ag(111) was identified. Though the calculated structural parameters for the layer spacing of the adsorbate relative to the nearest Ag layer and the S-Ag bond lengths are reasonable consistent with the experimental results, difference exists about the height corrugation in the S layer. Our results show that the buckling of the S layer observed in experiment might not represent the true atomic positions

Adsorption of Si on Cu(100) and (111) surfaces

Employing the density-functional theory within the generalized gradient approximation, we investigate the interaction between atomic Si and the Cu(100) and (111) surfaces. Various structures of on-surface adsorption as well as surface-substitutional adsorption for a wide range of Si coverage are considered. Our results show that both Cu(100) and (111) surfaces are active for adsorption of Si. The c(2 x 2)-Si/Cu(100) surface alloy is energetically favourable for a large range of Si chemical potential while c(2 x 2)-Si/Cu(111) is energetically favourable only under Si rich conditions

Ge adsorption on Pt(100) and Pt(111) surfaces: A density-functional study

Employing first-principles density-functional-theory generalized-gradient-approximation (DFT-GGA) calculations we have systematically investigated the adsorption of Ge on both Pt(100) and (111) surfaces, We considered both pure on-surface and surface-substitutional adsorption for a wide range of Ge coverage. Our results show that both surfaces are active towards adsorption of Ge, A significant repulsive interaction between Ge adatoms is also identified which causes the adsorption energy to decrease with increasing coverage. and on-surface adsorption becomes energetically unfavorable for coverage greater than about 0,5 monolayer on the (100) surface. At low Ge coverage both surfaces behave differently: on-surface adsorption is more preferential on (100) while substitutional adsorption is more favorable on (111), The reason for this qualitatively different behavior at the two surfaces is explained in terms of the structural and electronic effect,, that take place upon adsorption

Electronic Structure of Strained layer Superlattice GaN AlN

采用有效质量理论6带模型，计算了应变层超晶格gAnAln（001）的电子结构，具体计算不同应变状态的价带子能带色散曲线、光吸收曲线。分析了应变状态以及重轻空穴和自旋轨道分裂带相互作用对子带结构的影响。The electronic structure of strained layer superlattice GaN AlN(001) has been studied within framework of the 6 band Luttinger model in the effective mass theory. The valence band structure and the absorption spectra for different strain conditions are calculated. The effects of strain and coupling among heavy hole, light hole, and spin split off bands on valence band structure are discussed.福建省自然科学基金;厦门光电子工业部资

Calculation of Optical Properties of Zinc blende GaN,AlN and Their Alloys Ga 1 x Al x N

闪锌矿结构gAn、Aln和合金gA1-XAlXn光学性质计算何国敏王仁智郑永梅（厦门大学物理学系厦门361005）随着人们对发光二极管和半导体激光器等光电器件的深入研究，工作于蓝紫波段的半导体材料受到普遍的重视.宽带隙半导体gAn和Aln正是目前蓝紫...The nonlocal empirical pseudopotential method has been used to calculate the electronic structure of GaN, AlN and their alloys Ga 1 x Al x N .The imaginary part of the dielectric function of alloys Ga 1 x Al x N is also calculated with the virtual crystal approximation,and its trend versus Al fraction x are also discussed.国家和福建省自然科学基金;厦门大学光电子公司工业部资

The Static Properties of AlN and GaN,and the Valence-band ofFsets of AlN/GaN Heterojunction

采用lMTO能带从头计算方法，计算了闪锌矿（立方）结构AIn和gAn的静态性质；用平均键能方法，预言了Aln与gAn自由应变生长、以Aln为衬底和以gAn为衬底等三种不同应变状态下Aln/gAn应变层异质结的△EV值；最后，采用超原胞（AIn）n（gAn）n（001），（n=1，3，5）界面自洽计算方法，考察了超晶格中平均键能EM的“对齐”程度和验证了价带偏移△EV计算结果的准确性。The static properties of cubic AlN and GaN (zinc-blende structure) are calculated by ab initio LMTO method.Using average bonding energy method,the valence-band ofFsets of AlN/GaN strained layer heterojunction under three strained conditions (i.e.growing GaN layer on substrate of AlN,growing AlN layer on substrate of GaN,and AlN and GaN strained Freely to Form the hetero-junction) are predicted.Finally, the calculated results of valence-band ofFsets △Ev and the "alignment" of average bonding energy Em in strained layer superlattice (AlN )n (GaN)n (001), (n = 1,3, 5) are veriFied by supercell selF-consistent calculation.福建省自然科学基

没食子酸衍生物对蘑菇酪氨酸酶的抑制机理

蘑菇褐变过程主要是由于其酪氨酸酶的催化作用引起的,寻找该酶抑制剂在食品保鲜和储藏中的应用具有重要的意义.作者在实验中,发现没食子酸十二烷基酯和没食子酸香叶酯对蘑菇酪氨酸酶有较强的抑制作用,测定它们抑制蘑菇酪氨酸酶二酚酶的酶活力下降50%的抑制剂浓度(IC50)分别为1.55和0.25 mmol/L.显示没食子酸香叶酯的抑制作用强度是没食子酸十二烷基酯的6倍.研究了这两种抑制剂对蘑菇酪氨酸酶的抑制作用动力学,结果表明:没食子酸十二烷基酯和没食子酸香叶酯对酶的抑制作用均表现为可逆反应,前者为反竞争性,其抑制常数KIS为0.636 mmol/L;而后者为混合型,抑制常数KI和KIS分别为0.133和0.453 mmol/L

Structural and electronic properties of RuSi, RuGe and OsSi

Structural and electronic properties of RuSi, RuGe and OsSi are investigated by first-principle density-functional calculations based on ultrasoft pseudopotential and generalized gradient approximations for the exchange-correlation functional. The bulk moduli for RuGe and OsSi which have not been available from experiments are predicted to be 2.08 and 2.65 Mbar. Though all these compounds with a B20 structure are semiconductors according to the calculation, their band gaps are overestimated compared to those from experiments by a factor of about two

Valence Subband Structure and Optical Gain of InGaAs/InP Quantum Wire

采用有效质量理论 6带模型 ,计算了 In0 .53Ga0 .4 7As/ In P量子线的光学性质 ,具体计算了In0 .53Ga0 .4 7As/ In P量子线的能带结构、态密度、载流子浓度、光学跃迁矩阵元和光学增益谱 ,并把量子线的光学增益谱和量子阱的光学增益谱作了比较。福建省自然科学基金资助课题 (No.E9910 0 0 5