Lattice dynamics

Phonon spectrum of La$_2$Ge$_2$O$_7$: ab initio calculation

V. A. Chernyshev, V. P. Petrov

Ural Federal University named after the First President of Russia B. N. Yeltsin, Yekaterinburg, Russia

Abstract: Within the framework of the density functional theory ab initio calculation of the crystal structure, phonon spectrum, and elastic properties of lanthanum germanate La$_2$Ge$_2$O$_7$ with a triclinic structure (sp. gr. $P\bar{1}$, no. 2) was carried out. The frequencies and types of fundamental modes are determined. From the analysis of the displacement vectors obtained from the calculation, the degree of participation of ions in each mode was determined. The calculations were performed for the first time. Experimental data on the IR and Raman spectra, as well as the elastic constants of La$_2$Ge$_2$O$_7$, are absent in the scientific press. We used the CRYSTAL17 program designed for ab initio calculations of periodic structures within the framework of the MO LCAO approach.

Keywords: rare-earth germanates, phonons, elastic constants, hybrid functionals.

Received: 22.04.2022
Revised: 22.04.2022
Accepted: 28.04.2022

DOI: 10.21883/FTT.2022.08.52707.301

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