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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur
KFM 6: Poster
KFM 6.2: Poster
Tuesday, March 28, 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 VLi′, 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.