Thermal and geometric properties of alloy clusters studied with Brownian-type isothermal molecular dynamics simulations

We report a Brownian isothermal molecular dynamics simulation study of bimetallic clusters. Beginning at their lowest energy structures which were obtained from a recently developed algorithm [P. J. Hsu and S. K. Lai, J. Chem. Phys. 124, 044711 (2006)], we investigate the effect of temperature on the thermal and geometric of CuₘAu_n-m at given nuclearity n. We study in particular the change in temperature of the relative root-mean-squared bond length fluctuation δ so-called Lindemann parameter and exploit the underlying mechanism that leads to its thermal variation. We then discuss the correlation of δ to the specific heat which is used generally to deduce the bulklike melting of bimetallic clusters. The mismatch quite often seen at the melting temperature between δ and specific heat can now be understood better.