Abstract
We measured the temperature-dependent equilibrium vacancy concentration using in situ positron annihilation spectroscopy in order to determine the enthalpy and entropy 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 and : in particular is one order of magnitude larger compared to other elemental metals, and the experimental value of is found to be more than three standard deviations off the theoretical one (our DFT calculation for La at ). A consistent explanation is given beyond the classical Arrhenius approach in terms of a temperature dependence of the vacancy formation entropy with accounting for the anharmonic potential introduced by vacancies.
- Received 22 January 2020
- Accepted 24 March 2020
DOI:https://doi.org/10.1103/PhysRevB.101.134105
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