Accelerating and stabilizing the convergence of vibrational self-consistent field calculations via the direct inversion of the iterative subspace (vDIIS) algorithm

Emily L Yang; Ryan J Spencer; Asylbek A Zhanserkeev; Justin J Talbot; Ryan P Steele

doi:10.1063/5.0160363

Accelerating and stabilizing the convergence of vibrational self-consistent field calculations via the direct inversion of the iterative subspace (vDIIS) algorithm

J Chem Phys. 2023 Aug 28;159(8):084103. doi: 10.1063/5.0160363.

Authors

Emily L Yang^{1

2}, Ryan J Spencer^{1

2}, Asylbek A Zhanserkeev^{1

2}, Justin J Talbot³, Ryan P Steele^{1

2}

Affiliations

¹ Department of Chemistry, The University of Utah, 315 S 1400 E, Salt Lake City, Utah 84112, USA.
² Henry Eyring Center for Theoretical Chemistry, The University of Utah, 315 S 1400 E, Salt Lake City, Utah 84112, USA.
³ Department of Chemistry, University of California-Berkeley, 420 Latimer Hall, Berkeley, California 94720, USA.

PMID: 37606324
DOI: 10.1063/5.0160363

Abstract

The vibrational self-consistent field (VSCF) method yields anharmonic states and spectra for molecular vibrations, and it serves as the starting point for more sophisticated correlated-vibration methods. Convergence of the iterative, non-linear optimization in VSCF calculations can be erratic or altogether unsuccessful, particularly for chemical systems involving low-frequency motions. In this work, a vibrational formulation of the Direct Inversion of the Iterative Subspace method of Pulay is presented and investigated. This formulation accounts for distinct attributes of the vibrational and electronic cases, including the expansion of each single-mode vibrational wavefunction in its own basis set. The resulting Direct Inversion of the Iterative Subspace method is shown to substantially accelerate VSCF convergence in all convergent cases as well as rectify many cases where Roothaan-based methods fail. Performance across systems ranging from small, rigid molecules to weakly bound molecular clusters is investigated in this analysis.