Friday, May 24, 2013

1305.5416 (Robert M. Horton et al.)

New Methods for Calculating the Free Energy of Charged Defects in Solid

Robert M. Horton, Andrew J. Haslam, Amparo Galindo, George Jackson, Michael W. Finnis
A methodology for calculating the contribution of charged defects to the configurational free energy of an ionic crystal is introduced. The temperature-independent Wang-Landau Monte Carlo technique is applied to a simple model of a solid electrolyte, consisting of charged positive and negative defects on a lattice. The electrostatic energy is computed on lattices with periodic boundary conditions, and used to calculate the density of states and statistical-thermodynamic potentials of this system. The free energy as a function of defect concentration and temperature is accurately described by a regular solution model up to concentrations of 10% of defects, well beyond the range described by the ideal solution theory. The approach, supplemented by short-ranged terms in the energy, is proposed as an alternative to free-energy methods that require a number of simulations to be carried out over a range of temperatures.
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