摘要
在用KSM方法对分子相互作用能量的分解过程中由于轨道间的相互影响 ,使分解的能量各分量之和不等于总的相互作用能 ,即产生偶合项 .用能级位移算符逐步改变某些特定轨道的能级 ,可以逐步解除对这些特定轨道的冻结 ,从而可以减少以至完全消除轨道间的相互影响 ,即消除偶合项 ,使能量分解结果清晰。
In the scheme of energy decomposition analysis of KSM, the interaction energy between the deformed monomers A and B, E-int, is decomposed into four components and coupling term among various interaction components E-int = ES + EX + CTPLX (A-->B) + CTPLX (B-->A) + MIX Here ES is the electrostatic interaction between the electron distributions of the isolated monomers, EX is the exchange repulsion energy, CTPLX (A-->B) is the donation interaction and the CTPLX (B-->A) is the back-donation interaction. For some strong interactions, the coupling term MIX becomes large in magnitude. The reason of large MIX is that the donation and back-donation may influence each other, so that the combined effect of CTPLX(A-->B) and CTPLX (B-->A) is different from the sum of each taken alone. In order to eliminate the coupling tern, we define a one-electron shift operator F-k= Sigma(st)A(st)((k)) \ phi(s) > h(k) < phi(t)\ , where h(k) is a constant, A(st)((k)) are determined by < phi(i) \F-k\ phi(j) > = Sigma(st)A(st)((k)) < phi(i) \ phi(s) > h(k) < phi(t) \ phi(j) > = h(k)delta(ik)delta(jk). The operator F-k can shift the chosen orbital \ phi(k) > by h(k) only and not affect other orbitals. If h(k) is chosen as positive infinity, \phi(k) > will be deleted in molecular wavefunction at all because of its infinity high energy. When h(k) increases gradually from zero to infinity, orbital \ phi(k) > will be gradually deleted from molecular wavefunction progressively. Using this shift operator the energy levels of virtual orbitals of the fragments A and B can be gradually increased in turn, and correspondingly the virtual orbitals of A and B can be gradually deleted in turn. In this way the mutual influence between the donation and back-donation (MIX) can be decreased and finally be eliminated. The transition-metal complex Ni (PH3)(2)(C2H4) is discussed as an example.
出处
《化学学报》
SCIE
CAS
CSCD
北大核心
2003年第2期156-160,共5页
Acta Chimica Sinica
