Thermodynamics of small mercury clusters and the role of electronically excited states: a case study on Hg-13

Abstract

Classical Monte Carlo simulations in the isothermal-isobaric ensemble have been performed for the Hg-13 cluster with the main emphasis paid to structural changes in this cluster induced by elevated temperature and pressure. Broad ranges of temperatures and pressures have been considered so that a comprehensive picture of the structural changes in Hg-13 could be obtained and represented in the form of a phase diagram constructed in the temperature-pressure plane. The effect of the complex electronic structure of the cluster on its electronic ground state potential energy surface and equilibrium thermodynamics has been studied within a semi-empirical electronic structure model based on the diatomics-in-molecules approach. The involvement of (three) lowest excited electronic states has been revealed while the higher excited states available within this model do not contribute.