2024/11/11 by Stephen H. Yuwono, Yuwono, Stephen H., Run R. Li +7 · 4 citations
Engineering · Medicine · Physics and Astronomy · #Atomic and Molecular Physics #Chemical Physics (physics.chem-ph) #FOS: Physical sciences #Photocathodes and Microchannel Plates #Radiation Therapy and Dosimetry
paper · pdf · doi:10.48550/arxiv.2411.07341
openalex publication_date 2024/11/11 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
We present an implementation of relativistic ionization-potential (IP) equation-of-motion coupled-cluster (EOMCC) with up to 3-hole--2-particle (3h2p) excitations that makes use of the molecular mean-field exact two-component (mmfX2C) framework and the full Dirac--Coulomb--Breit Hamiltonian. The closed-shell nature of the reference state in an X2C-IP-EOMCC calculation allows for accurate predictions of spin-orbit splittings in open-shell molecules without breaking degeneracies, as would occur in an excitation-energy EOMCC calculation carried out directly on an unrestricted open-shell reference. We apply X2C-IP-EOMCC to the ground and first excited state of the HCCX+ (X = Cl, Br, I) cations, where it is demonstrated that a large basis set (i.e., quadruple-zeta quality) and 3h2p correlation effects are necessary for accurate absolute energetics. The maximum error in calculated adiabatic IPs is on the order of 0.1 eV, whereas spin-orbit splittings themselves are accurate to ≈ 0.01 eV, as compared to experimentally obtained values.