Orthogonality-constrained variational calculation of excited state wavefunctions and energies. A new strategy based on the method of simulated annealing

Abstract

A new method based on simulated annealing is developed for the variational determination of excited state wavefunctions which are constrained to remain orthogonal to the lower lying states of the same symmetry. The method is simple and effective. It does not require information about either the gradient or the Hessian matrix and is potentially capable of moving out of a local minimum and reaching a more global minimum. Encouraging results of some model calculations are reported.