We present molecular dynamics simulations of the absorption spectra of the Hg-2 molecule in solid neon, argon, and xenon. The simulations were performed using classical molecular dynamics (MD) and a diatomic-in-molecules (DIM) treatment of the mixing of the different states of Hg-2 induced by the environment. The experimental relative shifts of the X0(g)(+)-D1(u) transition band are qualitatively well reproduced. The origin of these shifts is identified as the result of two combined factors: the effect of the host onto the Hg-Hg equilibrium distances and the different interaction of each matrix with the Hg-2 electronic states. (C) 2002 Elsevier Science B.V. All rights reserved.