First principle investigation of the structural and electronic properties of the gallium clusters and their influence on the melting characteristics

First principle calculations have been performed to understand the experimentally observed size sensitive variations in the characteristics of heat capacities of gallium clusters [G. A. Breaux {\it et. al.} J. Am. Chem. Soc., {\bf 126}, 8628 (2004)]. It was reported that while some clusters exhibit a clear solid like to liquid like transition others exhibit a continuous transition with no peak in the heat capacity curve. In addition, the clusters also exhibit a variation of about 300 K (500--800 K) in the melting temperature across the size range of 20 to 46. In the present work we correlate the observed finite temperature properties to its geometry and nature of bonding in the ground state. We demonstrate that the local order (i.e., island of atoms bonded with similar strength) in the ground state geometry is responsible for the variation in the shape of the heat capacity curve. We attribute the higher melting temperature of clusters to the presence of distinct core and strong covalent bonds between the core and surface atoms.