Free-energy correction due to center-of-mass constraint in crystals.
The evaluation of the free-energy correction DeltaF(CM) involved in lifting the center-of-mass constraint to compute the free energy of crystalline solids is discussed. The key quantity in this correction, the probability density of the center of mass, p(0), is computed for a few model systems, and its main features are discussed. We argue that previous works on this problem, based on the Frenkel and Ladd method, have misinterpreted the correction, leading to an incorrect thermodynamic limit for the free energy. The impact of this error is quantitatively small. However, the unknown functional dependence of p(0) on density, number of particles, and geometry of simulation box makes problematic the correct evaluation of the thermodynamic limit.
Navascués
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Departamento de Física Teórica de la Materia Condensada and Instituto de Ciencia de Materiales Nicolás Cabrera, Universidad Autónoma de Madrid, E-28049 Madrid, Spain. guillermo.navascues@uam.es
Velasco
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