改进的EHMO理论Ⅱ.通式及其在异核双原子分子和多原子分子上的应用

本文将前文提出的对EHMO理论改进的校正因子(I_p~O-Y_p)e~(-a/2R)推广应用于异核双原子分子和多原子分子。用异核双原子分子LiH,NaH,KH,CuH,MgH,CaH,OH,HCl,HF,BeO,NaCl,NaNe和多原子分子BrCN,CH_4,CH_3F,,考核了改进EHMO理论的计算通式,得到了较满意结果。结果表明,经改进后的EHMO计算通式,用于研讨分子的稳定空间构型时,所得结果与实验值间误差不大于30％。     

STRUCTURES OF Si AND Ge CLUSTERS UNDER MODIFIED STILLINGER-WEBER POTENTIAL

Structural behaviors of silicon and germanium clusters under the recently proposed modified Stillinger-Weber (SW) potential have been studied by molecular dynamics method along with the con-jugate-gradient optimization. Since the SW potentials have been derived from the properties of bulk materials, it gives relatively large discrepancy when the cluster number is small, e.g. n=3 and 4. When n>4, the ground-state structures under the modified SW potential are close to that from the first-principle calculation. The binding energies are also improved under the modified SW potential. These results may be attributed to the relative enhancement of the two-body term over the three-body term in the modified SW potential, which leads to structures with a preferential coordination number 4. Structural behaviors of germanium clusters are similar to those of silicon.     

β-C3N4,β-Si3N4和β-Ge3N4的能带结构

采用基于密度泛函理论的线性丸盒轨道原子球近似(LMTO-ASA)从头计算方法,研究了β-C₃N₄,β-Si₃N₄和β-Ge₃N₄的能带结构,得到了它们的能隙分别为:4.1751,5.1788和4.0279eV。对于β-C₃N₄,由于N的部分2p电子占据了非键轨道,禁带宽度较窄;对于β-Si₃N_{4关键词：}     

多孔硅尺寸的理论研究

研究了球形纳米硅的振动特性及Raman谱，建立了Raman移动与尺寸的对应关系．用球形纳米硅来模拟多孔硅，发现多孔硅的尺寸比通常认为的尺度要小得多 关键词：     

H在Al(111)面上吸附的多重散射Xα自洽计算

利用多重散射X_α自洽场方法研究了H在Al(111)表面吸附的桥位和顶位模型。结果表明顶位吸附的结合能优于桥位。顶位吸附中H的1s电子与Al相互作用形成不同形式的σ键,本文分析了这些成键细节,并给出了顶位吸附的态密度。 关键词：     

A THEORETICAL MODEL FOR H2 DISSOCIATIVE ADSORPTION ON Cu SURFACES

A theoretical model for describing H₂ dissociative chemisorption on Cu surfaces is proposed. The sticking probability S is calculated as a function of vibrational state, average kinetic energy and incident angle of hydrogen molecular beam. Within the theoretical frame of this model, the different contributions to S from H₂(v = 0) and H₂(v = 1) can be clearly distinguished. The calculated results indicate that vibrational energy significantly promotes the chemisorption of H₂ on Cu surfaces in the region of low translational energy. The equations derived can be used to analyze the experimental data for both pure and seeded molecular beams.     

BAND STRUCTURES OF Si-C AND Si-C-Ge ALLOYS

Band structures of Si-C and Si-C-Ge alloys are calculated by using the ab initio LMTO (linear muffin-tin orbital) method within the framework of atomic-sphere approximation. The effects of different atomic configuration and lattice relaxation on the band structure of alloys are taken into account. The results show that for large concentrations of C in Si and Si-Ge, the band gap increases monotonically, while for small concentrations of C in Si and Si-Ge, the band gap shrinks. The lattice relaxation further reduces the band gap. The possible explanations for the reduction of band gap of Si-C and Si-C-Ge alloya are presented.     

CO和NO在CuO及Cu2O(110)表面吸附选择规律研究

采用离散变分Xα方法分别计算了CO和NO以C（或N）端顶位吸附在CuO（110）及Cu2O（110）表面上的基态势能曲线,结果表明：CO在Cu2O表面上的吸附强,而在CuO表面上的吸附弱;NO则在CuO表面上吸附强,在Cu2O表面上吸附弱．它们的吸附能的大小顺序为：CuO－NO＞Cu2O－CO＞Cu2O－NO＞CuO－CO．对于CuO－NO（或CO）吸附体系,主要是Cu的3d轨道与吸附分子的2π轨道间的相互作用;对于Cu2O－CO（或NO）吸附体系,则主要是吸附质分子的5σ及2π分子轨道与其顶位Cu1的4s及4p轨道和侧位Cu2的3d轨道相互作用．本文通过吸附势能曲线、态密度分析、成键分析及电荷转移量和方向等方面对实验现象做了合理的解释．     

我国大学计算物理教学情况

由于计算物理学科在国际和国内的迅速发展,将计算物理学列入高等学校教学内容,已作为一个迫切问题提到日程上来。计算物理学会十分重视这方面的宣传、推广和组织工作。1984年11月计算物理学会在长沙召开了计算物理教材交流会议。当时开设计算物理课程的学校还很少。     

Rh超薄膜在Mo(111)及W(111)上引起{110}小面再构的可能性

用第一性原理总能计算方法,计算了Mo和W表面吸附金属Rh薄膜前后[111],[110]方向的表面能.计算结果表明,清洁Mo和W的（111）面不会发生{111}小面再构,与实验观察一致,当Rh的覆盖厚度达到一物理单层后,Rh/Mo（111）仍不会形成{110}小面;面Rh/W（111）满足小面再构到{110}的热力学条件,在一定条件下可能形成{110}小面. 关键词：