A first-principles method to model perturbed electronic wavefunctions: theeffect of an external homogeneous electric field

In this Letter, we show that with the use of matrix notation to express the time-independent Schroedinger equation, it is possible to model perturbed electronic wavefunctions. Such a method makes use of first principles of th e quantum mechanical theory and hence is rigorous within the only approxima tion due to the truncation of the perturbed Hamiltonian matrix used. Result s show that for three different molecules in vacuo under an electric field, the proposed method provides reliable perturbed electronic wavefunctions a t a low computational costs. (C) 2001 Elsevier Science B.V. All rights rese rved.