On the evaluation of non-adiabatic coupling matrix elements for large scale CI wavefunctions

Abstract

The implementation of a recently proposed technique for evaluating matrix elements of the form 〈Ψ J ( r; R)|∂Ψ I ( r; R)/t6 R α〉 r using analytic gradient techniques is described. The Ψ K ( r; R) are developed from state-averaged multiconfiguration self-consistent-field/configuration interaction (CI) wavefunctions. The CI wavefunctions are determined using the shape driven graphical unitary group approach. The method is shown to be considerably more efficient than presently existing approaches based on divided differences. As an illustration of the potentialities of this approach non-adiabatic coupling matrix elements are determined for the collinear charge transfer reaction: Mg( 1S) + FH( 1Σ +)→MgF( 2Σ +)+H( 2S).