基于密度泛函紧束缚方法的SixGey（n=x+y，n=2~5）团簇成键条件与解离行为研究

采用基于密度泛函理论的紧束缚方法和遗传算法相结合的方法对SixGey（x+y=n，n=2~5）二元团簇的低能稳定结构进行了全局搜索，分析了包含不同原子数目、不同组分团簇的几何构型、原子间交叠电子布居数及可能发生的解离行为。研究表明，包含2~5原子团簇的Si-Si、Ge-Ge和Si-Ge键的成键距离分别为2.18 Å ~ 3.10 Å、2.32 Å ~ 3.64 Å和2.32Å ~ 3.38 Å；二元团簇的原子数目、组分对原子间键长、键角及Si/Ge原子在团簇中的占位、原子间相互作用有明显影响。通过团簇中各原子的Mülliken总交叠电子布居数分析，发现多数团簇中单独的Ge原子最容易被解离出来，随着团簇包含原子数目增多，出现了多种存在竞争机制的解离方式，可能同时存在解离出Si1Ge1、Si2Ge1和Ge原子的情况。     

Coupled Channels Optical Method Study for Elastic Scattering Process of Electron-N2 Collisions

Different cross sections for the elastic scattering of electrons by N2 at impact energies of 10, 15, 20, 30, 40eV have been calculated and compared with the experimental data and other theoretical results. The present results are obtained by the momentum space coupled channels optical method. In this method, the e-molecule system has a single centre and the interaction of e-nuclei is expanded by a multipole expansion.     

β石墨炔衍生物结构稳定性及电子结构的密度泛函理论研究

石墨炔衍生物比石墨烯具有更多样化的原子结构,因而具有潜在的更丰富的电子结构.通过第一性原理密度泛函理论研究方法系统研究了β石墨炔衍生物的结构稳定性、原子构型和电子结构.本文计算的β石墨炔衍生物系列体系由六边形碳环(各边原子数N=1—10)通过顶点相连而成.对结构与能量的计算分析表明:当N为偶数时,β石墨炔拥有单、三键交替的C—C键结构,其能量比N为奇数时,拥有连续C=C双键的石墨炔衍生物更稳定.计算的能带结构和态密度显示:根据碳环各边原子个数N的奇偶性不同,β石墨炔可呈现金属性(N为奇数时)或半导体特性(N为偶数时).该奇偶依赖的原子构型和电学性质是由Jahn-Teller畸变效应导致,与碳环各边原子碳链的实际长度无关.计算发现部分半导体β石墨炔(N=2,6,10)呈现狄拉克锥能带特征,其带隙约10 meV,且具有0.255×10~6—0.414×10~6m/s的高电子速度,约为石墨烯电子速度的30%—50%.本密度泛函理论研究表明,将sp杂化碳原子引入石墨烯六边形碳环的边上,可通过控制六边形各边原子个数的奇偶性调制其金属和半导体电子特性或狄拉克锥的形成,为免掺杂和缺陷调控纳米碳材料的电学性质和设计碳基纳米电子器件提供了理论依据.     

Calculations of state-selective differential cross sections for charge transfer in collisions between O3+ and H2

The non-dissociative charge-transfer processes in collisions between O^3＋ and H2 are investigated by using the quantum-mechanical molecular-orbital coupled-channel （QMOCC） method. The adiabatic potentials and radial coupling matrix elements utilized in the QMOCC calculations are obtained with the spin-coupled valence-bond approach. Electronic and vibrational state-selective differential cross sections are presented for projectile energies of 0.1, 1.0 and 10.0eV/u in the H2 orientation angles of 45° and 89°. The electronic and the vibrational state-selective differential cross sections show similar behaviours： they decrease as the scattering angle increases, and beyond a specific angle the oscillating structures appear. Moreover, it is also found that the vibrational state-selective differential cross sections are strongly orientation-dependent, which provides a possibility to determine the orientations of molecule H2 by identifying the vibrational state-selective differential scattering processes.