Free-particle Green's function matrix elements over spherical Gaussian and plane-wave-modulated Gaussian basis functions

TL;DR

This paper develops a new analytical framework for calculating matrix elements of the free-particle Green's function using spherical Gaussian and plane-wave-modulated Gaussian basis functions, enhancing quantum scattering computations.

Contribution

It introduces a general, efficient method for evaluating Green's function matrix elements over Gaussian basis functions, addressing previous limitations in practical applications.

Findings

Derived compact closed-form expressions for matrix elements.

Established recurrence relations for efficient computation.

Analyzed asymptotic behavior for low-energy electron states.

Abstract

Free-particle Green's function plays a central role in the theoretical description of electron scattering and autoionization processes in quantum physics and chemistry. Recently, Gaussian basis set approaches have become increasingly important in applications to unbound and metastable electronic states. However, the practical use of such methods has been limited by the lack of efficient and compact analytical expressions for matrix elements of the free-particle Green's function in Gaussian-based representations. Here we present a novel, general analytical framework for the evaluation of one- and two-center matrix elements of the free-particle Green's function over spherical Gaussian basis functions and plane-wave-modulated spherical Gaussians. The derivation is based on the Fourier transform of Gaussian functions together with the addition theorem of harmonic polynomials, leading to compact closed-form expressions and efficient recurrence relations. We also analyze the asymptotic behavior of the free-particle Green's function matrix elements, which is essential in the description of low-energy continuum electrons using finite Gaussian basis sets.