AlH_n(n=1—3)的分子结构和AlH_3热力学稳定性  

Molecular structure of AlH_n(n=1—3) and thermodynamic stability of AlH_3

作　　者：谌晓洪[1,2] 朱正和[3] 高涛[3] 罗顺忠[4] 

机构地区：[1]西华大学物理实验中心 [2]四川大学原子分子物理研究所,成都610065 [3]四川大学原子分子物理研究所 [4]中国工程物理研究院

出　　处：《物理学报》2006年第7期3420-3432,共13页Acta Physica Sinica

基　　金：中物院重大基金(批准号:2003Z0501);国家自然科学基金(批准号:10376022)资助的课题.~~

摘　　要：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AlHn(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,同分子的阳离子比中性分子的Al—H键长短,也就是说H原子数越多,Al原子对H原子吸引越强,电子云越向Al原子靠近,失去一个电子的阳离子比中性原子的电子云更靠近Al原子.但它们得到一个电子的阴离子,却没有这个规律.计算表明在低温下,AlH3的平衡压力高于NiH的平衡压力,但是AlH3的平衡压力仍然相当低,同时,AlH3的De=9.3705eV,在298.15K时的ΔG0=-163.373kJ,因此,AlH3在热力学上应是比较稳定的.问题在于AlH3易于部分离解出氢气,导致发生化学变质.可否储存在含一定氢(在爆炸极限之外)的气氛中而保持较稳.Geometric configurations and harmonic frequencies of AIH. （ n = 1-3） molecule, their univalent cation and univalent anion have been calculated by means of h31yp 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 = 1-3） and their univalent cation shorten with the H atom numbers increasing in AlH, 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： De = 9.3705eV, △G^0= - 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.

关 键 词：AlH3分子 平衡几何结构 垂直电离能 垂直电子亲和能 

分 类 号：O561.1[理学—原子与分子物理]