Thermodynamics of carbon-doped Al and Ga clusters: ab initio molecular dynamics simulations

We have carried out extensive first principles thermodynamic simulations for Al13, Ga13, Al12C, and Ga12C. The results are based on the simulation time of 2.4 ns for each of the clusters, and the heat capacity curves have been calculated using multiple-histogram technique. Both clusters Al13 and Ga13 show higher than bulk melting temperatures. Upon doping, there is a substantial reduction in the melting temperatures of the host clusters. In the case of Ga, the carbon atom changes the geometry from decahedral to icosahedral. This change in the geometry changes the heat capacity curve significantly, making the solidlike to liquidlike transition sharper. Our results bring out the fact that an impurity can be used to tune the finite temperature properties of small clusters