Theoretical investigation of methane under pressure

摘要: We present computer simulations of liquid and solid phases condensed methane at pressures below 25 GPa, between 150 300 K, where no appreciable molecular dissociation occurs. used dynamics (MD) metadynamics techniques, empirical potentials in the rigid molecule approximation, whose validity was confirmed a posteriori by carrying out it ab initio MD for selected pressure temperature conditions. Our results melting line are satisfactory agreement with existing measurements. find that fcc crystal transforms into hcp structure 4 molecules per unit cell (B phase) about 10 GPa B phase monoclinic high above 20 GPa. solid/solid transitions consistent those Raman studies but boundaries estimated our calculations higher than inferred from spectroscopic data.