Regensburg 2019 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 34: Methods in Computational Materials Modelling (methodological aspects, numerics)
MM 34.4: Talk
Thursday, April 4, 2019, 11:00–11:15, H44
Phase stability of dynamically disordered solids from first principles — Johan Klarbring and •Sergei Simak — IFM, Linköping University, SE-581 83, Linköping, Sweden
Dynamically disordered solid materials show immense potential in applications. In particular, superionic conductors are very promising as solid state electrolytes in batteries and fuel cells. The biggest obstacle in living up to this potential is the limited stability of the dynamically disordered phases. To obtain the free energies of disordered materials has long been a challenge. We outline a method that offers a solution [1]. It is based on a stress-strain thermodynamic integration on a deformation path between a mechanically stable ordered variant of the disordered phase, and the dynamically disordered phase itself. We show that the large entropy contribution associated with the dynamic disorder is captured in the behavior of the stress along the deformation path.We apply the method to Bi2O3, whose superionic δ-phase is the fastest known solid oxide ion conductor. We accurately reproduce the experimental transition enthalpy and the critical temperature of the phase transition from the low temperature ground state α phase to the superionic δ phase. The method can be used for a first-principles description of the phase stability of superionic conductors and other materials with dynamic disorder, when the disordered phase can be connected to a stable phase through a continuous deformation path.
[1] J. Klarbring and S. I. Simak, Phys. Rev. Lett. 121, 225702 (2018).