Theory Studies on Low-Lying States of Lead Chalcogenide Cations

In this work, we investigate the low-lying states of PbS, PbSe, and PbTe cations based on a recently developed equation-of-motion coupled-cluster approach for ionization potentials (EOMIP-CC) with spin-orbit coupling (SOC) at the CCSD level. Equilibrium bond lengths, harmonic frequencies as well as vertical and adiabatic ionization energies are calculated with EOMIP-SOC-CCSD and reasonable agreement with available experimental data is achieved. The contribution of triples is estimated by comparing results at the CCSD(T) level with those from EOMIP-CCSD when SOC is neglected. Better agreement with experimental data can be obtained if the contribution of triples is included. According to our results, the splitting between