Effects of Thermal Fluctuation on Structures of Microclusters

Abstract

The thermodynamical properties of a 4-site model microcluster are investigated. It is shown that the thermal fluctuation of the structural degrees of freedom has a large amplitude so that the melting, that is, the excitation of all the structural degrees of freedom of interests takes place easily. The large amplitude of the structural fluctuation is characteristic in a small particle because of a large portion of surface atoms which are free from the strong constraint acting on bulk atoms. On the other hand, the electronic properties at finite temperatures are very suggestive of those of a bulk solid. The effect of the quantum fluctuation on the distorted structure in the ground state is discussed in relation to the broken symmetry.