NH3…H2O体系氢键团簇结构的从头计算方案比较

对H2O，NH3单分子以及反式线性NH3…H2O双分子团簇应用HF，DFT，MR2，CCD ，QCISD等从头计算方法在不同的基组水平上进行几何结构优化和氨—水分子间相 互作用能计算。比较实验值和计算结果表明：对氨—水体系，MP2／6-31+G^**方法 能够满足氢键N-0键长误差为0．004nm，键角∠NOH误差为1°，NH3…H2O相互作用 能△E与CCD和QCISD偏差2．1kJ／mol计算精度的要求，并有较合理的计算代价。

A Comparison of ab initio Calculation Methods on the Structure of NH3-"H2O Hydrogen- bonded Cluster

The ammonia, water monomer and the trans- linear NO hydrogen- bonded cluster have been studied using ab initio calculations. The geometries of these molecules are optimized at HF, DFT, MP2, CCD and QCISD levels with several basis sets, and the interaction energies are compared to the experimental and high level computational results. The results show that, to ammonia- water cluster, calculations at the MP2/6-31 + G level bring a reasonable computational consumed cost and can give a reliable result : the errors of NH hydrogen- bond length and bond angle ^/NOH are less than 0.4 nm and 1°, respectively; the NH3'*-H20 interaction energy differs only 2.1 kj/mol from CCD and QCISD methods