Free energies of crystals computed using Einstein crystal with fixed center of mass and differing spring constants

Khanna, V. and Anwar, J. and Frenkel, D. and Doherty, M.F. and Peters, B. (2021) Free energies of crystals computed using Einstein crystal with fixed center of mass and differing spring constants. Journal of Chemical Physics, 154 (16): 164509. ISSN 0021-9606

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Free energies of crystals computed using a center of mass constraint require a finite-size correction, as shown in previous work by Polson et al. [J. Chem. Phys. 112, 5339-5342 (2000)]. Their reference system is an Einstein crystal with equal spring constants. In this paper, we extend the work of Polson et al. [J. Chem. Phys. 112, 5339-5342 (2000)] to the case of differing spring constants. The generalization is convenient for constraining the center of mass in crystals with atoms of differing masses, and it helps to optimize the free energy calculations. To test the theory, we compare the free energies of LiI and NaCl crystals from calculations with differing spring constants to those computed using equal spring constants. Using these center of mass finite size corrections, we compute the true free energies of these crystals for different system sizes to eliminate the intrinsic finite-size effects. These calculations help demonstrate the size of these finite-size corrections relative to other contributions to the absolute free energy of the crystals.

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Journal Article
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Journal of Chemical Physics
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Copyright 2021 American Institute of Physics. The following article appeared in The Journal of Chemical Physics 154, 2021 and may be found at This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
Uncontrolled Keywords:
?? crystalsiodine compoundslithium compoundssodium chloridesprings (components)center of masseinstein crystalfinite size effectfinite-size correctionsfree-energy calculationsnacl crystalreference systemsspring constantsfree energyphysical and theoretical che ??
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17 May 2021 09:25
Last Modified:
17 Feb 2024 01:14