Gold-standard coupled-cluster study of the ground-state chromium dimer cation

We have first performed ‘gold-standard’ CCSD(T) calculations of the chromium dimer cation using a cc-pVQZ basis set in order to elucidate its electronic structures, especially for identification of its ground-state term. Our CCSD(T)/cc-pVQZ calculations have predicted that it is the highest-spin state, in contrast to a previous speculation of the lowest-spin state by density functional theory with semi-local functionals. The ground-state binding energy is found to be 1.49 eV, which reasonably agrees with the corresponding experimental value of 1.30 ± 0.06 eV. We have also provided several spectroscopic constants for references in future theoretical and experimental works.