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MM: Fachverband Metall- und Materialphysik

MM 37: Materials for Energy Storage and Conversion - Structure of Battery Materials

MM 37.4: Vortrag

Mittwoch, 18. März 2020, 12:30–12:45, IFW D

First-principles investigation of a LISICON-to-LGPS phase transition in Li₁₀GeP₂O₁₂ — •Giuliana Materzanini and Nicola Marzari — Theory and Simulations of Materials (THEOS) and National Centre for Computational Design and Discovery of Novel Materials (MARVEL), École Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland

Using ab-initio molecular dynamics, we have recently reported a remarkably high Li-ion conductivity (σ ≃ 10⁻³S/cm at 25^∘C, E_a = 0.21 eV) for the oxide analogue of Li₁₀GeP₂S₁₂ (LGPS, tetragonal P4₂/nmc). Though not being reported in the experimental literature so far, this system possesses the same density and stoichiometry of the LISICON Li_3.33Ge_0.33P_0.66O₄ (orthorhombic Pnma), that oppositely shows low conductivity (σ ≃ 10⁻⁶S/cm at 25^∘C, E_a = 0.54 eV). Aim of this work is shedding light on a possible phase transition from the existing orthorhombic phase to a tetragonal phase of Li₁₀GeP₂O₁₂ (LGPO). We use variable-cell (NPT) Car-Parrinello molecular dynamics (CP package of the QUANTUM ESPRESSO distribution) at 600K, 1200K an 1500K. Simulations are conducted starting from both the tetragonal ideal LGPS structure (t-LGPO) and the existing orthorhombic structure (o-LGPO). Although t-LGPO has higher enthalpy than o-LGPO at all temperatures, at 1200K o-LGPO undergoes phase transitions, possibly driven by the higher entropy and Li-ion conductivity of the phases formed during the dynamics. Structural similarities with t-LGPO of these phases are discussed, and their conductivities at 600K assessed through NPT and NVT simulations.