Modeling of supramolecular structure and dielectric properties of methanol from melting point to supercritical state

The supramolecular structure and dielectric properties of pure fluid methanol are modeled in the temperature range from melting point to supercritical state using the Quasichemical Model of the Nonideal Associated Solution (QCNAS). Two models of supramolecular structure are compared as regards their performance to reproduce experimental data on dielectric permittivity of methanol. The first model includes only chain-like aggregation while the second one takes into account both chain-like and cyclic methanol aggregates. Dielectric permittivity and dipole correlation factor of methanol are calculated in the temperature interval 177-593 K with pressure ranging from 0.1 to 20 MPa. Both models proved quite adequate in reproducing experimental data for pure methanol, but including cyclic aggregates of methanol is essential for consistency with the models for methanol mixtures. The thermodynamic and structural parameters of supramolecular aggregates are reported. Distribution functions of aggregates over size and structure are evaluated in the entire temperature range. Long supramolecular aggregates with long range molecular correlations extending far beyond the nearest coordination shells are revealed.