Equation-of-motion coupled-cluster variants in combination with perturbative triples corrections in strong magnetic fields

TL;DR

This paper implements advanced coupled-cluster methods with perturbative triples corrections to study electronic states and properties of atoms and molecules in strong magnetic fields, aiding spectral analysis of white dwarf stars.

Contribution

The authors developed and implemented EOM-CCSD and non-perturbative triples correction schemes for strong magnetic fields, enabling detailed electronic structure analysis of atoms and molecules in such environments.

Findings

Access to a wide range of electronic states in strong magnetic fields.

Analysis of ionization potentials and electron affinities for elements in magnetic fields.

Insights into the electronic structure of molecules relevant to white dwarf atmospheres.

Abstract

In this paper, we report on the implementation of the EOM spin-flip (SF), ionization-potential (IP) and electron-affinity (EA) coupled cluster singles doubles (CCSD) methods for atoms and molecules in strong magnetic fields for energies as well as one-electron properties. Moreover, non-perturbative triples corrections using the EOM-CCSD(T)(a)* scheme were implemented in the finite-field framework for the EE, SF, IP, and EA variants. These developments allow the access to a large variety of electronic states as well as the investigation of IPs and EAs in a strong magnetic field. The latter two indicate the relative stability of the different oxidation states of elements. The increased flexibility to target challenging electronic states and the access to the electronic states of the anion and cation are important for the assignment of spectra from strongly magnetic White Dwarf (WD) stars. Here, we investigate the development of the IPs and EAs in the presence of a magnetic field for the elements of the first and second row of the periodic table. In addition, we study the development of the electronic structure of Na, Mg, and Ca that aided in the assignment of metal lines in a magnetic WD. Lastly, we investigate the electronic excitations of CH in different magnetic-field orientations and strengths, a molecule that has been found in the atmospheres of WD stars.