Hybrid quantum/classical simulation of the vibrational relaxation of the bend fundamental in liquid water

Abstract

The Ehrenfest method with quantum corrections is used to describe the vibrational relaxation of the bend fundamental in liquid water. All the vibrational degrees of freedom of the water molecules are described using quantum mechanics, while the remaining translational and rotational degrees of freedom are described classically. The relaxation time obtained compares well with experiment and with relaxation times calculated using other theoretical approximations. The presence of resonant intermolecular vibrational energy (VV) transfer is established with a maximum percentage of excited molecules, different from the initial one, of 9.2%. It is found through an effective kinetic fit that two VV transfers occur before relaxation of water to the vibrational ground state.