We introduce a new scheme for molecular-dynamics simulation of three-dimens
ional systems exhibiting rotational motions. The procedure is based on the
Langevin dynamics method. Our paper is focused on the Lebwohl-Lasher model
in order to simulate the isotropic-nematic transition of liquid crystals. I
n contrast to previous dynamic approximations, our approach allows one to r
eproduce well the isotropic phase of these systems.