等电子-等自旋与非等旋反应的G2(MP2)和G2研究

我们在前文［1－2］中分别用MP2－4／6－31G**／／MP2／6－31G**及MP4／6－311G（2df，Zpd）／／MP2／6－31G**研究了一些双原子氢化物、卤化物、硫化物和氧化物的化学反应的烂变·这些化学反应按如下类型分为四组，即（1）反应物与生成物之间为等电子一等自旋关系，（2）价层等电一等旅，（3）等施和（4）非等旅·结果表明，MP4／6－3fiG（2才，ZPd）对于（1），（2）和（3）类反应，基本上与实验误差小于士15kJ·mo－‘而对非等旋反应仍有较大误差；MPZ－4／6－31G””只对（1）类反应较好．由于PoPle等人近几年来创立的Gaussi…

G2(MP2) and G2 Study of the Energies of the Iso-electronic, Isogyric and Non-isogyric Reactions

Enthalpy changes of the reactions involved in our previous papers have been re-examined at the G2(MP2) and G2 levels. The G2(MP2) and G2 energies of Ar, Ar+,ArAr+, ArCl+, ArF+, ArH+, ArHe+, ArNe+, ArO+, ArS+, H2+, He, HeCl+, HeF+, HeO+,HeS+, Ne, NeCl+, NeF+, NeO+ and NeS+ have been calculated. The G2(MP2) and G2 results for all of the interested reactions have also been compared with those of the previous MP2/6-31G** and MP4/6-311G (2df, 2pd) calculations. All of the G2(MP2) and G2 reaction enthalpies are improved from the MP2 and MP4 level of calculations when compared with the experimental data for the four categories of reactions as (1) iso-electronic, iso-gyric; (2) valence isoelectronic, isogyric; (3) and (4)non-isogyric reactions with the average absolute deviations of 5.10, 4.60, 7.70 and 9.20 for G2(MP2) and 4.18, 5.19, 6.78 and 6.49kJ?mol-1 for G2, respectively. The individual deviation for almost all of the reactions involved in this work is not more than ±13 kJ?mol-1 for G2(MP2) and ±8.4 kJ?mol-1 for G2. In this paper, an additional number of reactions examined at the G2(MP2) and G2 levels as well as at the MP2/6-31G** and MP4/6-311G(2df, 2pd) levels of calculations have also been reported. The MP2, MP4, G2(MP2) and G2 total energies for the interested chemical species have been calculated if these energies have not been reported in literatures. All of the reaction energies at different levels have been compared with the experimental data in a number of reactions devided into the above four categories. The average absolute deviations are 25.9, 36.0, 29.2 and 40.1 for MP2; 8.41, 18.3, 17.2 and 18.3 for MP4; 9.41, 5.98, 4.85 and 6.90 for G2(MP2) and 6.69, 4.06, 3.85 and 4.60 kJ?mol-1 for G2, respectively. It is clear that the MP2 calculation did quite poor for all of the four categories of reactions and the MP4 did well only for the isoelectronic and isogyric reactions. The G2(MP2) and G2 reproduce the experimental reaction enthalpy changes very well for all reactions in the four categories. The individual deviation for almost all of the reactions involved in this work is not more than ±13 kJ?mol-1 for G2(MP2) and ±8.4 kJ?mol-1 for G2 while it may be more than ±84 kJ?mol-1 for MP2/6-31G**.