Advantages and limitations of Kohn-Shm orbitls as single electron basis for multireference configuration interaction and multireference perturbation theory

摘要

In the present work we study the performance of orbitals form an effective exact exchange-only optimized potential method,the localized Hartree-Fock approach,in multireference ab initio mehthods.In the first part local Hartree-Fock orbitals are used to describe the excited states of carbon monoxide,formaldehyde,and acetone in multireference configuration interaction calculations.The local Hartree-Fock orbitals are compared with standard Hartree-Fock orbitals,and those from a gradient corrected and a hybrid density functional.This part mainlytries to analyze possible deficiencies of the local Hartree-Fock orbitals.In the second part of this work the above-mentioned orbitals are testedin multireference perturbation theory second-order.We test to which extent known deficiencies of single state perturbation theory seocnd-order.We test to multireference approaches,and hten study how well local Hartree-Fock orbitals perform in multireference perturbation theory seocnd-order computations of excitd states.