AlHn(n=1—3)的分子结构和AlH3热力学稳定性

在gaussian03基础上，分别用b3lyp和qcisd方法，在6-311++g^**基组水平上研究了AlH_n(n=1—3)分子及其一价阴阳离子的几何结构和谐振频率，计算了它们中性分子的离解能，第一垂直电离能，电子亲和能. 并与可能得到的实验值及文献上的理论计算值进行了比较. 发现qcisd方法得到的数据更接近实验值. 计算发现对AlH，AlH₂和AlH₃分子及其1价阳离子的Al—H键长，随着H原子数的增多，键长越短， 关键词： 3分子')" href="#">AlH₃分子 平衡几何结构 垂直电离能 垂直电子亲和能

Molecular structure of AlHn ( n = 1-3) and thermodynamic stability of AlH3

Geometric configurations and harmonic frequencies of AlH_n(n=1—3) molecule, their univalent cation and univalent anion have been calculated by means of b3lyp and qcisd methods at 6-311++g^** level with Gaussian03 software packages. Dissociation energies, first vertical ionization energies, electron affinities of the neutral molecules are studied. We compared the above theoretical values with experimental values and other theoretical values from literatures, and found that the values from qcisd method are closer to experimental values, the bond length of AlH_n(n=1—3) and their univalent cation shorten with the H atom numbers increasing in AlH_n molecule. That is to say, the Al atom attracts H atoms stronger as the number of the H atoms increases and electronic cloud are closer to aluminum atom. The computational results show that the equilibrium pressure of AlH₃ is higher than that of NiH, but it is rather low still. For the AlH₃ molecule we have the results: D_e=9.3705eV,ΔG⁰=-163.373kJ at 298.15K, so the AlH₃ molecule is more stable thermodynamically. The problem is that AlH₃ molecule is easier to dissociate and produce hydrogen gas. It may be stable if preserved in hydrogen gas environment.