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Relativistic Complete Active Space Self-consistent-Field Method with a Hierarchy of Exact Two-Component Hamiltonians

Xubo Wang, Sen Wang, Yixuan Wu, Lan Cheng

Abstract

The development of a novel exact two-component (X2C) scheme with the inclusion of the picture-change correction for the fluctuation potential, the X2Ccorr scheme, is reported, hereby establishing a hierarchy of X2C schemes with systematic improvement for the treatments of relativistic two-electron contributions. Using benchmark X2C complete active space self-consistent-field (CASSCF) calculations for zero-field splittings in chalcogen diatomics, the contributions of two-electron spin-orbit coupling, electron spin-spin coupling, and quantum electrodynamics are carefully analyzed. The capability of the new Cholesky decomposition-based implementation for relativistic two-component CASSCF method using super-configuration-interaction algorithms is further demonstrated with calculations for the low-lying electronic states of neodymium aqua-ions with up to the second coordination shells.

Relativistic Complete Active Space Self-consistent-Field Method with a Hierarchy of Exact Two-Component Hamiltonians

Abstract

The development of a novel exact two-component (X2C) scheme with the inclusion of the picture-change correction for the fluctuation potential, the X2Ccorr scheme, is reported, hereby establishing a hierarchy of X2C schemes with systematic improvement for the treatments of relativistic two-electron contributions. Using benchmark X2C complete active space self-consistent-field (CASSCF) calculations for zero-field splittings in chalcogen diatomics, the contributions of two-electron spin-orbit coupling, electron spin-spin coupling, and quantum electrodynamics are carefully analyzed. The capability of the new Cholesky decomposition-based implementation for relativistic two-component CASSCF method using super-configuration-interaction algorithms is further demonstrated with calculations for the low-lying electronic states of neodymium aqua-ions with up to the second coordination shells.
Paper Structure (16 sections, 33 equations, 1 figure, 6 tables)

This paper contains 16 sections, 33 equations, 1 figure, 6 tables.

Table of Contents

  1. Introduction
  2. Theory
  3. A hierarchy of exact two-component (X2C) Hamiltonians
  4. The X2C schemes without the picture change for the fluctuation potential
  5. The "X2Ccorr" scheme
  6. Cholesky decomposition based relativistic two-component CASSCF method with super-CI algorithm
  7. The SCI scheme for two-component CASSCF
  8. The CD-based implementation
  9. Computational details
  10. Results and Discussions
  11. Zero-field splitting of chalcogen diatomics
  12. Spin-orbit and ligand-field splittings in Nd aquo-ions
  13. Spin-orbit splittings in the Nd^3+ ion embedded in point charges
  14. Ligand-field splittings in the Nd^3+ aquo-ions
  15. Summary and outlook
  16. ...and 1 more sections

Figures (1)

  • Figure 1: A hierarchy of X2C schemes with systematically improved treatments of relativistic two-electron contributions.