Strong chemical bonds to gold. High level correlated relativistic results for diatomic AuBe+, AuC+, AuMg+, and AuSi+

Calculations are reported for the singlet ground states of the four, experimentally unknown, title species. Relativistic effects are treated at the quasirelativistic Douglas–Kroll level. AuBe+, AuSi+ and AuC+ are calculated to have at CASPT2 level the largest De values known for gold, 3.636, 3.688 and 3.815 eV, respectively. AuC+ has a short bond, Re=176.6 pm. For AuC+, CCSD(T) reference data are also provided.