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Regular version of the site

Article

Lattice dynamics and structure of the new langasites Ln3CrGe3Be2O14 (Ln ¼ La, Pr, Nd): Vibrational spectra and ab initio calculations

Journal of Physics and Chemistry of Solids. 2020. Vol. 138. No. 109266. P. 1-6.
Кузьмин Н. Н., Климин С. А., Маврин Б. Н., Boldyrev K., Чернышев В. А., Милл Б. В., Popova M. N.

We present experimental (by means of the infrared absorption and Raman scattering measurements at room
temperature) and first-principles studies of the lattice dynamics of the recently discovered new compounds
La3CrGe3Be2O14, Pr3CrGe3Be2O14, and Nd3CrGe3Be2O14 belonging to the langasite series and constituting a new
class of low-dimensional antiferromagnets. The observed vibrational modes of all the three compounds are
consistent with the results of the group-theoretical analysis for the langasite structure (sp. gr. P321) established
earlier for La3CrGe3Be2O14 by the Rietveld refinement. Vibrational frequencies are uniformly distributed over the
spectral range ~80–840 cm􀀀 1. Frequencies and intensities of the modes were satisfactory modeled in the
framework of density functional theory and MO LKAO approach using the B3LYP hybrid functional which takes
into account the non-local exchange in the Hartree-Fock formalism. Analyzing the displacement vectors obtained
in the ab initio calculations, we estimate the degree of participation of each ion in each vibrational mode. Information
on the lattice dynamics of the title compounds is essential for a further research on the properties and
functionalities of these new low-dimensional magnets with frustrated interactions.