Mechanical, elastic and thermodynamic properties of crystalline lithium silicides

S Schwalbe and T Gruber and K Trepte and F Taubert and F Mertens and J Kortus, COMPUTATIONAL MATERIALS SCIENCE, 134, 48-57 (2017).

DOI: 10.1016/j.commatsci.2017.03.028

We investigated crystalline thermodynamic stable lithium silicides phases (LixSiy) with density functional theory (DFT) and a force-field method based on modified embedded atoms (MEAM) and compared our results with experimental data. Our objective is to provide a fast method besides the standard quasi harmonic approximation (QHA) utilizing DFT for large unit cells. For this purpose, we present a framework to calculate thermodynamic properties with MEAM based on molecular dynamics (MD), obtaining appropriate accuracy while significantly reducing computational cost. Mechanical properties like the bulk modulus and the elastic constants were evaluated in addition to thermodynamic properties including the phonon density of states, the vibrational free energy and the isochoric/isobaric specific heat capacity for Li, Li12Si7, Li7Si3, Li13Si4, Li15Si4, Li21Si5, Li17Si4, Li22Si5 and Si. For a selected phase (Li13Si4) we studied the effect of a temperature dependent phonon density of states and its effect on the isobaric heat capacity. (C) 2017 Elsevier B.V. All rights reserved.

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