(197bs) Prediction of Isomorphs By Using Configurational Temperature

When performing molecular dynamic simulations, lowering the time and energy spent on calculations can be very valuable. One way of reducing time spent on simulations is by eliminating the need of simulating systems at different conditions, which can be accomplished by identification of isomorphs¹. Isomorphs refer to a set of equivalent state points in which structure and dynamics are invariant. They effectively reduce a two-dimensional thermodynamic phase diagram to one dimension; this allows for the mapping of properties of a system at one point to another point without need of running a simulation at the other point. Currently, there are a number of methods used for isomorph identification, but the focus of the presented work is on the potential of using configurational temperature, T_conf², for isomorph identification.

The most fool-proof method of isomorph identification is the gamma (γ) method, in which the main property of an isomorph is employed – constant excess entropy along the isomorph. Although reliable, this method is expensive as it requires a simulation from which γ can be calculated, γ being the correlation coefficient between the potential energy function and the instantaneous virial¹. There are other methods for isomorph identification, all of which have varying degrees of speed compared to the γ method, but the focus of this work is on exploring the viability of using configurational temperature, T_conf, for isomorph identification, which requires only one equilibrated configuration from one simulation. To this end, we have seen success with single-particle Lennard-Jones systems, but the presented work expands to include one, two, and three component systems.

1. Chem. Phys. 131, 234504 (2009)
2. Phys. 103:10, 1361-1373 (2005)