A molecular dynamics study of vibrational relaxation in a diatomic molecular liquid

Abstract

In an effort to gain some insight into vibrational relaxation in liquids, a molecular dynamics investigation of a one‐dimensional model of a diatomic molecular liquid has been carried out. The model consists of 100 heteronuclear diatomics arranged head to tail. The potential energy binding the atoms of each diatomic is taken to be strictly harmonic. Only interactions between nearest atoms of neighboring diatomics are taken into account, and these are of the Lennard‐Jones (12,6) form. The vibrational lifetime τ′ and dephasing time τ have been computed for the system at various temperatures and densities. Both τ and τ′ decrease as the temperature increases at constant density or as the density increases at constant temperature. For all cases considered, τ<τ′. It is concluded that concerted collective motions apparently play a dominant role in vibrational relaxation in this system.