Convergence of gradient-based algorithms for the Hartree-Fock equations

TL;DR

This paper proves the convergence of gradient-based algorithms for solving the Hartree-Fock equations in quantum chemistry, providing theoretical guarantees and convergence rates for several algorithms.

Contribution

It offers the first complete convergence proofs for these algorithms, including the gradient, Roothaan, and Level-Shifting methods, with convergence rate estimates.

Findings

Proved convergence of a natural gradient algorithm using Lojasiewicz inequality.

Established convergence results for Roothaan and Level-Shifting algorithms.

Provided numerical comparisons validating theoretical convergence rates.

Abstract

The numerical solution of the Hartree-Fock equations is a central problem in quantum chemistry for which numerous algorithms exist. Attempts to justify these algorithms mathematically have been made, notably in by Cances and Le Bris in 2000, but, to our knowledge, no complete convergence proof has been published. In this paper, we prove the convergence of a natural gradient algorithm, using a gradient inequality for analytic functionals due to Lojasiewicz. Then, expanding upon the analysis of Cances and Le Bris, we prove convergence results for the Roothaan and Level-Shifting algorithms. In each case, our method of proof provides estimates on the convergence rate. We compare these with numerical results for the algorithms studied.