title: Monte Carlo simulations of fluids whose particles interact with a logarithmic potential.
abstract: Monte Carlo simulations of a model fluid in which the particles interact via a continuous potential that has a logarithmic divergence at a pair separation of sigma, which we introduced in J. G. Powles et al., Proc. R. Soc. London, Ser. A 455, 3725 (1999), have been carried out. The potential has the form, phi(r)= -epsilon ln(fr), where epsilon sets the energy scale and fr=1-(sigma/r)m. The value of m chosen was 12 but the qualitative trends depend only weakly on the value of m, providing it is greater than 3. The potential is entirely repulsive and has a logarithmic divergence as approximately -ln(r/sigma-1) in the r-->sigma limit. Predictions of the previous paper that the internal energy can be computed at all temperatures using the standard statistical mechanics formula for continuous potentials are verified here. The pressure can be calculated using the usual virial expression for continuous potentials, although there are practical limitations in resolving the increasingly important contribution from the r-->sigma limit at reduced temperatures greater than approximately 5. The mean square force F2 and infinite frequency shear Ginfinity and bulk Kinfinity moduli are only finite for T*=kBT/epsilon<1. The logarithmic fluid's physical properties become increasingly more like that of the hard sphere fluid with increasing temperature, showing a sharp transition in the behavior of the mean square force and infinite frequency elastic constants at T*=1. The logarithmic fluid is shown to exhibit a solid-fluid phase transition.
authors.affiliation: Division of Chemical Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford GU2 7XH, United Kingdom. d.heyes@surrey.ac.uk
authors.forename: D M
authors.initials: DM
authors.lastname: Heyes
authors.forename: G
authors.initials: G
authors.lastname: Rickayzen
authors.forename: J G
authors.initials: JG
authors.lastname: Powles
mesh_terms: D003102:Colloids / Q000737:chemistry*; D003198:Computer Simulation; D004574:Electromagnetic Fields; D044085:Microfluidics / Q000379:methods*; D008956:Models, Chemical; D015233:Models, Statistical; D009010:Monte Carlo Method; D017711:Nonlinear Dynamics; D010316:Particle Size
chemical_list: D003102:Colloids