When HgI2 is photodissociated, it produces a vibrationally hot ground state HgI molecule. Pugliano et al. have reported a T-1 time of similar to 3 ps for dipolar HgI in ethanol [J. Chem. Phys. 103, 6498 (1995)]. We have carried out equilibrium molecular dynamics simulation for the above system to calculate the T-1 time theoretically and to understand the nature of solvent forces giving rise to the relaxation. The solvent friction on the vibrational coordinate was calculated for dipolar and nonpolar HgI. The vibrational decay rate obtained from the simulation is in quantitative agreement with the experimentally determined value. The dissipation of excess vibrational energy in HgI is mainly facilitated by the Lennard-Jones force fluctuations. The structure and nature of the solvent molecules giving rise to these interactions are discussed in detail. The effects of anharmonicity, the similarity between the friction spectra and the optical Kerr spectra and the validity of the Landau-Teller formula are discussed.