SKM 2023 – wissenschaftliches Programm

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 6: Poster

KFM 6.2: Poster

Dienstag, 28. März 2023, 17:00–19:00, P3

Lithium vacancies concentration in LiNbO₃ from first principles — •Christa Fink, Felix Bernhardt, and Simone Sanna — Justus-Liebig-University, Giessen, Germany

Lithium niobate is known as a crystalline material with ferroelectric, piezoelectric, photorefractive, and electro-optical properties and therefore has multiple applications. One of the intrinsic point defects of LiNbO₃, the negatively charged Lithium vacancy V_Li′, is studied in this contribution from first principles. The isolated defect is investigated using density functional theory to calculate the temperature dependency of the defect concentration of Lithium vacancies in LiNbO₃ crystals. The defect concentration can be calculated assuming an Arrhenius behavior where the activation energy is given by the Gibbs energy of defect formation. The Gibbs energy itself is a sum of several terms which are all depending on temperature. Since ab initio calculations are always performed at T=0 K, a special formalism is used which allows adding a temperature dependency to the standard ab initio calculations. This formalism includes several approaches to take temperature into account. In addition, finite-size effects due to computational limitations need to be considered during the calculation of defect formation energies and formation entropies.