密度泛函理论研究簇合物(HFGaN3)n (n=1-6)：尺寸效应
DFT study of (HFGaN3)n (n=1-6) clusters: the size effect

用密度泛函理论DFT方法，计算研究不对称簇合物(HFGaN3)n (n=1-6)的几何构型、稳定性、IR谱和热力学性质。结果表明，簇合物(HFGaN3)n (n=2-6)的优化构型拥有一个Ga和α？N原子交替的2n元环状结构。通过计算研究(HFGaN3)n (n=1-6)的平均结合能、二阶能量差分和能隙与团簇尺寸关系，发现后两者表现出明显的“奇－偶”振荡现象。对计算获得的IR谱进行归属，获得四个特征区。讨论了团簇尺寸和温度对(HFGaN3)n (n=1-6)热力学函数的影响。由焓变和吉布斯自由能可知，200-800 K温度范围内由单体形成稳定的多聚体(HFGaN3)n (n=2-6)在热力学上有利。
The equilibrium geometries, stabilities, IR spectra, and thermodynamic properties of asymmetric clusters (HFGaN3)n (n=1-6) are studied using the density functional theory method (DFT). The optimized results suggest that the core structures of 2n-membered ring with alternating gallium and α-nitrogen atoms are observed in clusters when n≥2. The relative stabilities of (HFGaN3)n (n=1-6) clusters are analysed by means of the dependent relationships between the cluster size n and the averaged binding energies, the second-order difference of energies, the HOMO？CLUMO energy gaps, respectively, and a odd？Ceven alternation phenomenon is found for the latter two items. Four main characteristic regions are obtained and assigned for the calculated IR spectra. Trends in thermodynamic properties with temperature and cluster size n are discussed, respectively. Thermodynamic analysis of the gas-phase oligomerizations shows that formations of the most stable clusters (HFGaN3)n (n=2-6) from the monomer are thermodynamically favorable by the enthalpies and Gibbs free energies in the range of 200-800 K.