Dresden 2017 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 5: Computational Materials Modelling: Materials at finite temperatures

MM 5.5: Vortrag

Montag, 20. März 2017, 11:15–11:30, IFW B

Investigation of low temperature features in the heat capacity of metals — •Ankit Gupta¹, Bengü Tas Kavakbasi², Biswanath Dutta¹, Blazej Grabowski¹, Tilmann Hickel¹, Sergiy Divinski², Gerhard Wilde², and Jörg Neugebauer¹ — ¹Max-Planck-Institut für Eisenforschung, Düsseldorf, Germany — ²Inst. of Materials Physics, Univ. of Münster, Münster, Germany

Heat capacities are often used to assess the predictive capability of computational thermodynamics, since they are experimentally directly accessible and as second derivatives very sensitive to energy changes. Finite-temperature first-principles calculations have accurately described the heat capacity of various material systems up to the melting point. In contrast, their assessment for the competition and coupling between the electronic and vibrational excitation mechanisms in the low-temperature regime is still in its infancy.

In this work, we explore this competition and coupling in the heat capacity C_p below 20 K for the example of Al and Al₃Sc. In order to enhance the sensitivity with respect to low temperature features, we analyze C_p/Tⁿ for n=0, …, 3. We show that, density functional theory successfully resolves all the features observed in the recent experimental calorimetric data, including the low-temperature limit and localization effects in the heat capacity. The relevance of peaks in the phonon density-of-states beyond the Debye level and non-adiabatic electron-phonon coupling phenomena are evaluated. All mechanisms are found to be described accurately at the level of semi-local exchange-correlation functionals.