Simulation of the supramolecular organization and permittivity of methanol over a wide range of state parameters, including the supercritical region

Supramolecular structure models were suggested to describe the permittivity of methanol over a wide range of state parameters from the melting point to the supercritical region. The models were based on the quasi-chemical model of a nonideal associated solution. The permittivity and dipole correlation factor of methanol were calculated over the temperature range 177–593 K at pressures from 0.1 to 20 MPa for two supramolecular structure models. Methanol molecules formed chain associates according to the first model and chain and cyclic aggregates according to the second one. Both models successfully described the experimental data on pure methanol, but the inclusion of cyclic aggregates was necessary for consistency with models of methanol solutions in various solvents over the entire composition range. The thermodynamic and structural parameters of supramolecular aggregates were calculated. The particle-size distributions of aggregates and other integral and differential characteristics of association over the whole range of fluid methanol state parameters were determined for the first time.