On the bonding of Ga2, structures of Gan clusters and the relation to the bulk structure of gallium

On the dimeric nature of gallium and gallium clusters. ► DFT and CCSD (T) calculations of the structures of small gallium clusters agree closely on their overall geometries, bond lengths, and energies. This is important in light of their generally multi-reference nature. ► The singlet quadramer, Ga4, can be described as a (Ga2)2 molecule with bond lengths corresponding to those of the ground state and first excited state of the free dimers. Moreover, these bond lengths correspond to the first and second nearest neighbour distances in the bulk. This suggests that parametrisation of an intermolecular potential to describe the melting of bulk gallium may be possible - which would clearly support the description of gallium as a 'molecular metal'. ► The successful description of small gallium clusters with coupled cluster theory, and the similarity of these clusters to the bulk, show promise for the application of wavefunction-based correlation methods to the bulk lattice structure of gallium, as has previously been possible only for closed-shell metals.