Parametrization and validation of coarse grained force-fields derived from ab initio calculations

A novel multisite interaction potential, suitable for computer simulations of complex materials as liquid crystals or polymers, is proposed and parametrized. Its validation is achieved through Monte Carlo numerical experiments at constant temperature and pressure, performed on the p-n-phenyls series and a typical mesogenic molecule (5CB). The model is constructed by connecting an array of anisotropic Gay-Berne sites and a collection of isotropic Lennard-Jones sites. The former mimics the rigid planar six-membered rings of the molecule, while the latter represents the flexible chain, if present. Such intermolecular potential, coupled with an intramolecular part to account for molecular flexibility, is parametrized from ab initio information only, obtained through the recently proposed Fragmentation-Reconstruction Method (FRM). Computer simulations are performed on all systems by exploring phase behavior at several temperatures and by comparing the resulting thermodynamic and structural properties with the relevant experimental data. Despite the simplicity of the present models, the good agreement with the experimental measures suggests the possibility of adopting such hybrid potentials for those systems with a large number of atoms, where high computational cost does not allow the use of more accurate atomistic potentials.