Free energy calculations of elemental sulphur crystals via molecular dynamics simulations

Abstract

Free energy calculations of two crystalline phases of the molecular compound S8 were performed via molecular dynamics simulations of these crystals. The elemental sulphur S8 molecule model used in our MD calculations consists of a semi-flexible closed chain, with fixed bond lengths and intra-molecular potentials for its bending and torsional angles. The intermolecular potential is of the atom-atom Lennard-Jones type. Two free energy calculation methods were implemented: the accurate thermodynamic integration method proposed by Frenkel and Ladd and an estimation that takes into account the contribution of the zero point energy and the entropy of the crystalline vibrational modes to the free energy of the crystal. The last estimation has the enormous advantage of being easily obtained from a single MD simulation. Here we compare both free energy calculation methods and analyze the reliability of the fast estimation via the vibrational density of states obtained from constrained MD simulations. New results on alpha- and alpha'- S8 crystals are discussed

arXiv comment18 pages, 2 figures, submitted to J. Chem. Phys

References in corpus (4)

• Finite-size corrections to the free energy of crystalline solids
• Test of a simple and flexible molecule model for alpha-, beta- and gamma-S8 crystals
• Toward an anisotropic atom-atom model for the crystalline phases of the molecular S8 compound
• Test of a simple and flexible S8 model molecule in alpha-s8 crystals

Cited by in corpus (3)

• Study of pressure-induced amorphization in sulfur using \textit{ab initio} molecular dynamics
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• Effective potentials and electrostatic interactions in self-assembled molecular bilayers II: the case of biological membranes