Molecular dynamics simulation of the fragile glass former orthoterphenyl: A flexible molecule model. II. Collective dynamics - art. no. 021511

We present a molecular dynamics study of the collective dynamics of a model for the fragile glass former orthoterphenyl. In this model, introduced by Mossa, Di Leonardo, Ruocco, and Sampoli [Phys. Rev. E 62, 612 (2000)], the intramolecular interaction among the three rigid phenyl rings is described by a set of force constants whose value has been fixed in order to obtain a realistic isolated molecule spectrum. The interaction between different mo lecules is described by a Lennard Jones site-site potential. We study the b ehavior of the coherent scattering functions F-t(q,t), considering the dens ity fluctuations of both molecular and phenyl-ring centers of mass; moreove r we directly simulate the neutron scattering spectra taking into account b oth the contributions due to carbon and hydrogens atoms. We compare our res ults with the main predictions of the mode-coupling theory and with the ava ilable coherent neutron scattering experimental data.