Quasi harmonic lattice dynamics: the phase diagram of benzene Original Research Article

We present a quasi harmonic lattice dynamics calculation for the crystal structure and the phonon frequencies of orthorhombic and monoclinic benzene as a function of pressure and temperature. We employ a site-site potential model including Coulombic interactions, which were found necessary to obtain the correct low pressure phase. The calculations agree with the measurements in both phases and reproduce very well the experimental phase diagram. When applicable, quasi harmonic lattice dynamics is an accurate and extremely efficient method, which promises to outperform molecular dynamics and Monte Carlo simulations.