Breakdown of Arrhenius law of temperature-dependent vacancy concentration in fcc lanthanum

Lucian Mathes, Thomas Gigl, Michael Leitner, and Christoph Hugenschmidt
Phys. Rev. B 101, 134105 – Published 15 April 2020

Abstract

We measured the temperature-dependent equilibrium vacancy concentration using in situ positron annihilation spectroscopy in order to determine the enthalpy Hf and entropy Sf of vacancy formation in elementary fcc La. The Arrhenius law applied for the data analysis, however, is shown to fail in explaining the unexpected high values for both Sf and Hf: in particular Sf=16(2)kB is one order of magnitude larger compared to other elemental metals, and the experimental value of Hf is found to be more than three standard deviations off the theoretical one Hf=1.46eV (our DFT calculation for La at T=0K). A consistent explanation is given beyond the classical Arrhenius approach in terms of a temperature dependence of the vacancy formation entropy with Sf=0.01119(13)kB/K accounting for the anharmonic potential introduced by vacancies.

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  • Received 22 January 2020
  • Accepted 24 March 2020

DOI:https://doi.org/10.1103/PhysRevB.101.134105

©2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Lucian Mathes, Thomas Gigl, Michael Leitner, and Christoph Hugenschmidt*

  • Physik-Department and Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstraße 1, 85748 Garching, Germany

  • *christoph.hugenschmidt@frm2.tum.de

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Issue

Vol. 101, Iss. 13 — 1 April 2020

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