A first-principles method to model perturbed electronic wavefunctions: the effect 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 the quantum mechanical theory and hence is rigorous within the only approximation due to the truncation of the perturbed Hamiltonian matrix used. Results show that for three different molecules in vacuo under an electric field, the proposed method provides reliable perturbed electronic wavefunctions at a low computational costs.