Convergence of explicitly correlated gaussian wave functions

Abstract

Results of high precision quantum-chemical calculations on selected diatomic molecular systems are reported. The wave function is expanded in the basis of exponentially correlated Gaussian functions. For each of the systems the Schr¨odinger equation is solved variationally with several lengths of this expansion, which enables the energy convergence to be studied as well as an extrapolation to infinite basis set size and an error estimation to be performed. The algorithms applied to evaluate matrix elements and the matrix diagonalization are analyzed for their scalability, and their strong and weak points are revealed.