Geometry of methanol models investigated in this work. The diameters of the methyl group and of the oxygen atom correspond to and of model J2 reported in Table I, respectively. The distances among the interaction sites are, irrespective of the model, , , and ; .
(Color) MD (top) and RISM/HNC (bottom) site-site radial distribution functions at ambient conditions (, ) for all methanol models envisaged in this work. In the left panels, OH RDF are grouped on the left and CO RDF on the right; in the right panels, HH RDF are grouped on the left and OO RDF on the right; All distances are given in angstroms. Note the different vertical scale in the bottom-right panel.
(Color) MD (circles) and RISM/HNC (full lines) for the J2 model at ambient conditions. All distances are given in angstroms. In the top panels, the dashed lines correspond to the neutral model, i.e., with in Eq. (1). In the CC panel, the dotted line is the RDF of a LJ fluid. In the OH panel, the dotted line is obtained when the OH interaction is completely switched off. In the central panels, the running coordination numbers , see Eq. (6), are also shown (squares: MD; dashed line, RISM), with the corresponding scale on the right.
(Color online) RISM and MD equations of state (top) and free energy (bottom) for the J2 model at (left) and (right). Symbols in the legends. In the top panels smooth interpolations of the simulation data are also shown. The MD free energies are obtained by thermodynamic integration through Eq. (12) of the corresponding simulation pressures.
RISM/KH liquid-vapor coexistence points for the J1 (full squares) and J2 (full circles) models of methanol. Open symbols represent the corresponding Gibbs ensemble simulation results from Ref. 25. Interpolating curves are best fits of the theoretical predictions according to the scaling law for the densities and the law of rectilinear diameters, with the full diamonds indicating the critical points (see the text for more details).
Internal energy per particle, calculated for and various temperatures. Dotted, solid, and dashed lines are RISM predictions for models J1, J2, and H1, respectively. Squares, circles, and triangles are the corresponding MD data.14 Stars are present simulation results for the three models at .
Intermolecular potentials for liquid methanol. Parameters are taken from Ref. 15 for model J1, Ref. 16 for J2, and Refs. 14 and 24 for H1. Partial charges are given in units; in kcal/mol; in angstroms. In all models, and were originally set equal to zero; in the RISM calculations an extra repulsion is added between the O and H sites, see text.
RISM critical temperatures (in kelvins) and densities (in ) for all models envisaged in this work, together with the corresponding Gibbs ensemble Monte Carlo results of Ref. 25.
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