物理化学学报 >> 2000, Vol. 16 >> Issue (11): 1003-1012.doi: 10.3866/PKU.WHXB20001109

研究论文 上一篇    下一篇

G3(QCI)模型化学方法

苏克和, 魏俊, 胡小玲, 岳红, 吕玲, 王育彬, 文振翼   

  1. 西北工业大学化工系 西安 710072|西北大学现代物理所 西安 710068
  • 收稿日期:2000-03-16 修回日期:2000-06-05 发布日期:2000-11-15
  • 通讯作者: 苏克和 E-mail:sukehe@nwpu.edu.cn

G3(QCI) Model Chemistry Theoretical Procedures

Su Ke-He, Wei Jun, Hu Xiao-Ling, Yue Hong, Lv Ling, Wang Yu-Bin, Wen Zhen-Yi   

  1. Department of Chemical Engineering,Northwestern Polytechnical University,Xi'an 710072|Institute of Modern Physics,Northwest University,Xi'An 710068
  • Received:2000-03-16 Revised:2000-06-05 Published:2000-11-15
  • Contact: Su Ke-He E-mail:sukehe@nwpu.edu.cn

摘要:

建立了非微扰外推模式下的几种G3(QCI)方法:G3(QCI/fu1)、G3(QCI/fu2)、G3(QCI/ful)//B3PW91和G3(QCI/fu2)//B3PW91.其中,电子能量用QCISD(T,FC)/G3large直接计算,芯电子相关能分别在MP2/6-31G(d)和MP2/6-31G(d,p)级别上计算,对125个G2-1 test set 的计算结果表明,总体精度与G3和G3 //B3LYP相当;平均绝对偏差分别为4.370、4.389、4.061和4.022kJ mol-1,相应G3和G3//B3LYP分别为4.27和4.05kJ mol-1.文章提出的方法排除了G3中外推办法的不确定因素,且更适用于非平衡几何构型体系能量的定量计算。

关键词: 模型化学, 方法, G3(QCI/fu1) G3(QCI/fu2), G3(QCI/ful)//B3PW91, G3(QCI/fu2)//B3PW91

Abstract:

G3(QCI) model chemistry,which eliminates the uncertainties of basis sets and theoretical methods extrapolation approximations,is defined via eq.: E0[G3(QCI)]=E[QCISD(T,FC)/G3large]+Δ E(full)+ E(SO)+ E(ZPE)+ E(HLC) where the electronic energy E[QCISD(T,FC)/G3large] is directly calculated at QCISD(T,FC)/G3large level,the core electron correlation energyΔ E(full) is calculated at MP2/6-31G(d) (denoted as fu1) or MP2/6-311G(d,p) (denoted as fu2) level and the spin-orbit coupling E(SO) for atomic species is from the experiments as what has been done in the G3[2] theory.Four varieties of G2(QCI) model chemistry theoretical procedure,namely G3(qCI/fu1),G3(qCI/fu2),G3(QCI/fu1)//B3PW91;G3(QCI/fu2)//B3PW91,are proposed and tested with the G2-1 test set.The E(HLC)'s have been defined and optimized in the same manner as in G2 theory,which are -3.024na-5.397nβ on molecules and -2.085na-5.636nβ on atomic species for G3(QCI/fi1),-3.085na-5.478nβ on molecules and -1.885na-5.466nβ on atomic species for G3(QCI/fu2),-2.495na-5.478nβ on molecules and -1.70na-5.584nβ on atomic species for G3(QCI/ful)//B3PW91 and -2.670na-5.380nβ on molecules and -1.923na-5.465nβ on atomic species for G3(QCI/fu2)//B3PW91.The over-all accuracy is close to that of the G3 or G3/B3LYP method published in literature.The average absolute deviations on the G2-1 test set for these models are 4.37,4.39,4.06 and 4.02kJ mol-1,respectively,compared with 4.27 for G3 and 4.05 for G3//B3LYP on the same G2-1 test set.These results show further that the additivity or extrapolation approximation in the G3 theory is valid.However,the non-additive G3(QCI) procedures,which would be about four times of computer time consuming,in this work has been shown more reliable in the energy calculation of species at non-equiliberum geometry.Yhe maximum deveation of all of the four G3(QCI)'s occurs on the electronic affinity of the oxygen atom,e.g.-16.7 for G3(QCI/fu1) and -16.9kJ mol-1 for others compared with 17.6 for G3 and 18.4kJ mol-1 for G3//B3LYP on the electronic affinity of NH radical.In addition,this work suggests that the G3large basis sets for the first-row atoms are too small or the level of core-electronic energy calculations for the anions are too low since most of the larger errors are in the respective electronic affinities and this need to be further studied.

Key words: Model chemistry, Theoretical procedures, G3(QCI/fu1), G3(QCI/fu2), G3(QCI/fu1)//B3PW91, G3(QCI/fu2)//B3PW91