Is Au6 a circular ring?

Complete active space multiconfiguration self-consistent field followed by higher-order configuration interaction calculations reveal that the ground state of Au6 is of 1A1 symmetry with a capped pentagonal structure. Similar calculations on Au−6 are also made. The 1A1g state of the neutral Au6 with a ring structure (D6h) is found to be 1.36 eV above the capped-pentagonal structure while the 3T2g state with an octahedral geometry is 1.5 eV above the capped pentagon. We conclude that Taylor et al.’s photodetachment spectra of Au−6 results from detachment of an electron from the 2E1u excited state of Au−6 with a ring structure to yield the 1A1g state of neutral Au6 with the same structure, although this is not the ground state of Au6.