Dynamics of the Negative Thermal Expansion in Tellurium Based Liquid Alloys

Céline Otjacques, Jean-Yves Raty, Marie-Vanessa Coulet, Mark Johnson, Helmut Schober, Christophe Bichara, and Jean-Pierre Gaspard
Phys. Rev. Lett. 103, 245901 – Published 7 December 2009

Abstract

Negative thermal expansion (NTE) in tellurium based liquid alloys (GeTe6 and GeTe12) is analyzed through the atomic vibrational properties. Using neutron inelastic scattering, we show that the structural evolution resulting in the NTE is due to a gain of vibrational entropy that cancels out the Peierls distortion. In the NTE temperature range, these competing effects give rise to noticeable changes in the vibrational density of states spectra. Additional first principles molecular dynamics simulations emphasize the role of the temperature dependance of the Ge atomic environment in this mechanism. For comparison, we extended our study to Ge2Sb2Te5 and Ge1Sb2Te4 phase-change materials.

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  • Received 6 March 2009

DOI:https://doi.org/10.1103/PhysRevLett.103.245901

©2009 American Physical Society

Authors & Affiliations

Céline Otjacques1,*, Jean-Yves Raty1, Marie-Vanessa Coulet2, Mark Johnson3, Helmut Schober3, Christophe Bichara4, and Jean-Pierre Gaspard1

  • 1Condensed Matter Physics Laboratory, University of Liège, B5, B-4000, Sart-Tilman, Belgium
  • 2IM2NP - CNRS and Aix-Marseille Universities, Avenue Escadrille Normandie Niemen - Case 142 - 13397 Marseille Cedex 20, France
  • 3Institut Laue Langevin, BP 38042, BP 220, Grenoble Cedex, France
  • 4CINaM - CNRS and Aix-Marseille Universities, Campus de Luminy, Case 913, F-13288, Marseille - Cedex 9, France

  • *celine.otjacques@ulg.ac.be

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Vol. 103, Iss. 24 — 11 December 2009

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