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

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.