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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 14: Poster
KFM 14.16: Poster
Mittwoch, 19. März 2025, 17:00–18:30, P1
Thermodynamics of Barium Boranate using DFT — •Markus Mehlhorn1, Konrad Burkmann2, Angus Demmer2, Jakob Kraus1, Franziska Habermann2, Jürgen Seidel2, Klaus Bohmhammel2, Jens Kortus1, and Florian Mertens2 — 1Institut für Theoretische Physik, TU Bergakademie Freiberg — 2Institut für Physikalische Chemie, TU Bergakademie Freiberg
Materials containing high hydrogen content are interesting candidates for solid hydrogen storage. However, there are well-known fundamental challenges to address like the reversibility of the (de)-hydrogenation and sufficiently fast kinetics for these processes before possible applications. Here we present results on thermodynamic properties of Ba(BH4)2. Unfortunately, the isobaric heat capacity function of this material is not accessible experimentally. Ba(BH4)2 could not be synthesized in sufficient purity. Therefore we attempt to fill this gap by means of computations based on density functional theory using the PBEsol functional. The quasi harmonic approximation is used to describe volume expansion due to thermal effects assuming that for each fixed volume the harmonic approximation can be employed. For each volume the phonon density of states has been calculated via density functional perturbation theory. This procedure allows to calculate the Gibbs free energy and therefore gives access to thermodynamic properties like entropy and isobaric heat capacity. Comparing the heat capacity to other metal boranates, which have been synthesized and measured, one finds very similar behavior.
Keywords: DFT; Statistical Thermodynamics; Barium Boranate; Hydrogen Storage; Quasi Harmonic Approximation