Modeling ferroelectric LiNb1-xTaxO3 solid solutions and their defect structure
The goal of the present project is the theoretical description of LNT solid solutions over the whole composition range. Macroscopic materials properties are calculated from first principles on the basis of the microscopic structure. Thereby, we combine a long-standing experience in the modelling of ferroelectrics with substantial expertise in the field of atomistic calculations. Atomistic approaches offer the possibility to model artificial or experimentally not accessible structures to disentangle the complex physical processes that simultaneously act to determine the materials properties. Moreover, we model a multitude of directly measurable quantities, which allow for the direct connection of the present proposal to each experimental project. With the determination of structural and thermodynamic properties (e.g. lattice parameters, activation energies, diffusion coefficients, excess enthalpies) as well as linear and non-linear optical signatures (e.g. optical, Raman, second- and third-harmonic-spectra) we lay the basis for the thorough understanding of the investigated model system.
The aim of this project is the prediction of the composition dependent properties of the LNT ground state and its structural and electronic excitations. This enables us to understand the influence of structure, stoichiometry and doping on the macroscopic scale, and allows thereby the interpretation of the experimental results. This, in turn, puts us in the condition to propose optimal compositions of solid solutions with tailored electro-mechanical or electro-optical properties.