Interactions leading to disordered ground states and unusual low-temperature behavior

Robert D. Batten, Frank H. Stillinger, Salvatore Torquato

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

We have shown that any pair potential function v (r) possessing a Fourier transform V (k) that is positive and has compact support at some finite wave number K yields classical disordered ground states for a broad density range. By tuning a constraint parameter χ (defined in the text), the ground states can traverse varying degrees of local order from fully disordered to crystalline ground states. Here, we show that in two dimensions, the " k -space overlap potential," where V (k) is proportional to the intersection area between two disks of diameter K whose centers are separated by k, yields anomalous low-temperature behavior, which we attribute to the topography of the underlying energy landscape. At T=0, for the range of densities considered, we show that there is continuous energy degeneracy among Bravais-lattice configurations. The shear elastic constant of ground-state Bravais-lattice configurations vanishes. In the harmonic regime, a significant fraction of the normal modes for both amorphous and Bravais-lattice ground states have vanishing frequencies, indicating the lack of an internal restoring force. Using molecular-dynamics simulations, we observe negative thermal-expansion behavior at low temperatures, where upon heating at constant pressure, the system goes through a density maximum. For all temperatures, isothermal compression reduces the local structure of the system unlike typical single-component systems.

Original languageEnglish (US)
Article number031105
JournalPhysical Review E - Statistical, Nonlinear, and Soft Matter Physics
Volume80
Issue number3
DOIs
StatePublished - Sep 4 2009

All Science Journal Classification (ASJC) codes

  • Statistical and Nonlinear Physics
  • Statistics and Probability
  • Condensed Matter Physics

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