Uhlenbeck-Ford model: Phase diagram and corresponding-states analysis

Rodolfo Paula Leite, Pedro Antonio Santos-Flórez, and Maurice de Koning
Phys. Rev. E 96, 032115 – Published 11 September 2017

Abstract

Using molecular dynamics simulations and nonequilibrium thermodynamic-integration techniques we compute the Helmholtz free energies of the body-centered-cubic (bcc), face-centered-cubic (fcc), hexagonal close-packed, and fluid phases of the Uhlenbeck-Ford model (UFM) and use the results to construct its phase diagram. The pair interaction associated with the UFM is characterized by an ultrasoft, purely repulsive pair potential that diverges logarithmically at the origin. We find that the bcc and fcc are the only thermodynamically stable crystalline phases in the phase diagram. Furthermore, we report the existence of two reentrant transition sequences as a function of the number density, one featuring a fluid-bcc-fluid succession and another displaying a bcc-fcc-bcc sequence near the triple point. We find strong resemblances to the phase behavior of other soft, purely repulsive systems such as the Gaussian-core model (GCM), inverse-power-law, and Yukawa potentials. In particular, we find that the fcc-bcc-fluid triple point and the phase boundaries in its vicinity are in good agreement with the prediction supplied by a recently proposed corresponding-states principle [J. Chem. Phys. 134, 241101 (2011); Europhys. Lett. 100, 66004 (2012)]. The particularly strong resemblance between the behavior of the UFM and GCM models are also discussed.

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  • Received 7 April 2017
  • Revised 7 June 2017

DOI:https://doi.org/10.1103/PhysRevE.96.032115

©2017 American Physical Society

Physics Subject Headings (PhySH)

  1. Research Areas
Statistical Physics & ThermodynamicsCondensed Matter, Materials & Applied Physics

Authors & Affiliations

Rodolfo Paula Leite*, Pedro Antonio Santos-Flórez, and Maurice de Koning

  • Instituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas, UNICAMP, 13083-859 Campinas, São Paulo, Brazil

  • *rleite@ifi.unicamp.br
  • pasantos@ifi.unicamp.br
  • dekoning@ifi.unicamp.br

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Issue

Vol. 96, Iss. 3 — September 2017

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