The Generalized Occupation-Restricted-Multiple-Active-Space Concept in Multiconfigurational Self-Consistent Field Methods

TL;DR

The paper introduces GORMAS, a flexible multiconfigurational method that reduces computational complexity while maintaining accuracy, demonstrated on various molecular systems.

Contribution

GORMAS extends ORMAS by allowing pre- or post-restrictions, enabling more efficient active space selection in multiconfigurational calculations.

Findings

GORMAS achieves similar accuracy with significantly smaller reference spaces.

Test calculations on molecules show reduced computational cost.

GORMAS effectively manages active space selection for complex systems.

Abstract

A novel concept of multiconfigurational self-consistent field method, the generalized occupation-restricted-multiple-active-space (GORMAS) is presented. GORMAS wave functions are defined by substituting the complete active space (CAS) in ORMAS, given a pre- or a post-restriction. The GORMAS approach shows a flexible selection of active space, reduce the ineffective reference configurations from CAS dramatically. Test calculations in molecule or complex systems, CH$_2$O, (H$_2$O)$_2$ molecule, and oxoMn(salen) are presented. They show the GORMAS wave functions achieve the similar accuracy with under 15\% dimension of reference spaces.