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：     

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.     

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％。     

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.     

形变超晶格Si/Ge的能带结构

用经验的紧束缚方法对短周期的(Si)_n/(Ge)_m形变超晶格的电子态进行了计算。结果表明,由于布里渊区折迭的要求,只有当n+m=10时超晶格才可能产生直接能隙。对周期为n+m=10的超晶格,Γ,N,△处的导带谷间的相对位置对直接能隙的形成具有决定作用,而n的大小与衬底的组分对此有极大影响。(Si)₆/(Ge)₄和(Si)₈/(Ge)₂超晶格在Si_1-xG 关键词：     

H在Al(111)面上吸附的多重散射X_α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。     

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.