Dresden 2014 – scientific programme

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MM: Fachverband Metall- und Materialphysik

MM 15: Computational Materials Modelling III - Bulk thermodynamics/ Phase Transitions I

MM 15.2: Talk

Monday, March 31, 2014, 16:00–16:15, IFW D

Thermomechanical properties of α-iron from first-principles — •Daniele Dragoni¹, Davide Ceresoli², and Nicola Marzari¹ — ¹THEOS - École Polytechnique Fédérale, Lausanne, Switzerland — ²ISTM - Consiglio Nazionale delle Ricerche, Milano, Italy

Compliance tensors provide a full characterization of the mechanical response of crystals in the linear regime of stress-strain. Their prediction from first-principles is of great practical utility, given the large number of elastic constants that are not known experimentally, while also providing stringent tests for validation of electronic-structure approaches in those cases where accurate experimental numbers are available. Since the intrinsic temperature dependence of the elastic constants is determined by the vibrations of the crystal (a Bose-Einstein gas of harmonic oscillators), finite-temperature results can be computed, in the quasiharmonic approximation, from the equation of state for the materials at hand and the volume- or strain-dependence of the phonon frequencies. We use ferromagnetic bcc α-iron as a case study, carefully testing pseudopotential calculations against reference all-electron results at 0K, and cubic elastic constants at finite temperatures against experimental results.