Direct Determination of Optimal Real-Space Orbitals for Correlated Electronic Structure of Molecules

• DOI: 10.1021/acs.jctc.3c00732
• Publication Date: 2023-10-04T13:15:25Z
• Authors: Edward F. Valeev; Robert J. Harrison; Adam A. Holmes; Charles C. Peterson; Deborah A. Penchoff
• Keywords: Slater-type orbital; Localized molecular orbitals; STO-nG basis sets; Basis (linear algebra); Solver

We demonstrate how to determine numerically nearly exact orthonormal orbitals that are optimal for the evaluation of energy arbitrary (correlated) states atoms and molecules by minimization Lagrangian. Orbitals expressed in real space using a multiresolution spectral element basis is refined adaptively achieve user-specified target precision while avoiding ill-conditioning issues plague AO set expansions traditionally used correlated models molecular electronic structure. For light atoms, orbital solver, conjunction with variational structure model [selected Configuration Interaction (CI)] provides energies comparable state-of-the-art atomic CI solver. The computed significantly more accurate than counterparts obtained sets same rank expanded Gaussian bases, can be determined even when linear dependence preclude use bases. It feasible optimize 100 fully numerical on single computer node, significant room exists additional improvement. These findings suggest real-space representations might preferred alternative high-end materials.