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采用不同方法、在不同基组水平上系统地对(NH3)2缔合体进行构型优化和结合能计算,并和实验值做详细比较。(1)对于弱氢键体系(NH3)2,B3LYP和HF计算结果不可靠;(2)适合(NH3)2体系的最好计算方案是MP2/6-311++G**(如果基组不低于6-31++G**水平,计算结果也可取),但是必须做BSSE校正。(3)基组中不加弥散函数只能得到一种环状构型,加入弥散函数可以得到两种构型。(4)对于弱相互作用体系,在选用计算方法和基组前应该做充分的方法验证。
Different methods were used to systematically calculate the configuration optimization and binding energy of (NH3) 2 association at different levels and to compare with experimental values in detail. (1) The calculations for B3LYP and HF are unreliable for the weakly hydrogen-bonded system (NH3) 2; (2) The best calculation for the (NH3) 2 system is MP2 / 6-311 ++ G ** Not less than 6-31 ++ G ** level, the calculation result is also desirable), but BSSE calibration must be done. (3) There is only one kind of circular configuration without diffusion function in the basis set. Two kinds of configurations can be obtained by adding dispersion function. (4) For weak interaction systems, adequate method validation should be performed before choosing the calculation method and basis set.