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Four recently proposed intermolecular-potential models have been used in molecular-dynamics simulations of liquid methanol over a temperature range of approximately70K. Results are reported for thermodynamic and structural properties, self-diffusion coefficients, and reorientational correlation times. Two of the models are shown to give results in fair agreement with a wide variety of experimental data. The pattern of hydrogen bonding and the distribution of hydrogen-bond lifetimes in the simulated liquids have been investigated. The structure in each case is found to be dominated by winding chains, in agreement with earlier work. For the more realistic models, the mean hydrogen-bond lifetime at room temperature is approximately 1 to 2 ps, which is several times larger than the corresponding time for liquid water

We have been concerned thus far primarily with fluids in which the range of the interparticle forces is of the order of a few atomic radii. This chapter is devoted to systems in which the particles carry an electric charge. Ionic liquids have certain properties that are absent in fluids composed of neutral particles and many of their distinguishing features are associated in some way with the slow decay of the Coulomb potential. Our attention will be focused on three types of system: molten salts, ionic solutions and liquid metals. Molten salts are in many respects the simplest class of ionic liquids. We shall concentrate mostly on the case in which there is a single cation and a single anion species, of which the alkali halides are the best understood examples. Molten salts are characterised by large cohesive energies and high temperatures, and by ionic conductivities of the order of 1 −1 cm −1 . There exist also certain crystalline salts that have conductivities comparable with those of the molten phase. These are the so-called 'fast-ion' conductors, or 'solid electrolytes', in which one of the ionic species becomes liquid-like in behaviour above a certain temperature. Ionic solutions are liquids consisting of a solvent formed from neutral, polar molecules and a solute that dissociates into positive and negative ions. They vary widely in complexity. In the classic electrolyte solutions the cations and anions are of comparable size and absolute charge, whereas macromolecular ionic solutions contain both macroions (charged polymer chains, micelles, charged colloidal particles, etc.) and microscopic counterions. Despite their complexity some systems of the latter type, including charged colloidal suspensions, can be treated quantitatively by standard methods of liquid state theory, as we shall see in Chapter 12. Finally, liquid metals are similar in composition to molten salts, the anion of the salt being replaced by electrons from the valence or conduction bands of the metal. The analogy is a superficial one, however, because the small mass of the electron leads to a pronounced asymmetry between the two chargecarrying species. Whereas the behaviour of the ions can be discussed within the framework of classical statistical mechanics, the electrons form a degenerate Fermi gas for which a quantum mechanical treatment is required. The presence Theory of Simple Liquids, Fourth Edition. http://dx.