Numerical methods for computing ROHF ground states. Part I: SCF algorithms

Méthodes numériques pour le calcul d'états fondamentaux ROHF. Partie I : algorithmes SCF.

Robert Benda (1, 2) , Laurent Vidal (3, 2) , Emmanuel Giner (4) , Eric Cancès (3, 2)

1 LPICM - Laboratoire de physique des interfaces et des couches minces [Palaiseau]
2 CERMICS - Centre d'Enseignement et de Recherche en Mathématiques et Calcul Scientifique
3 ENPC - École des Ponts ParisTech
4 LCT - Laboratoire de chimie théorique

In this article, we propose a simple geometrical derivation of the restricted openshell Hartree-Fock (ROHF) equations in the density matrix formalism. We then introduce a new, parameter-free, basic fixed-point method to solve these equations, that, in contrast with existing self-consistent field (SCF) schemes, is not based on the introduction of a non-physical, parameter-dependent, composite Hamiltonian. We also introduce a variant of Pulay's DIIS algorithm specific to ROHF, and extend the Optimal Damping Algorithm to the ROHF framework. We finally present numerical results on challenging systems (complexes with transition metals) demonstrating the performance of the new algorithms we propose.

Domaines: Chimie; Mathématiques [math]; Physique [physics]; Informatique [cs]

Robert Benda, Laurent Vidal, Emmanuel Giner, Eric Cancès. Numerical methods for computing ROHF ground states. Part I: SCF algorithms. inPress. ⟨hal-03228618v1⟩