Lattice dynamics and elastic properties of lanthanum monopnictides

Abstract

a b s t r a c tIn this study, first principles calculation results of the second order elastic constants and lattice dynamics of two lanthanum monopnictides, LaN and LaBi, which crystallize in rock-salt structure (B1 phase), are presented. Calculations were based on plane wave basis sets and pseudopotential methods in the framework of Density Functional Theory (DFT) with generalized gradient approximation. Elastic constants are calculated by tetragonal and orthorhombic distortions on cubic structure. Phonon dispersion spectra was constructed in the linear response approach of the Density Functional Perturbation Theory (DFPT). The complete phonon softening with negative frequencies and large elastic anisotropy were observed for LaN single crystal as a sign of the structural instability. The phonon dispersion curve for LaBi is typical for lanthanum monopnictides and does not show any anomalous physical property. The calculated structural quantities for both LaN and LaBi systems agree well with the available experimental and theoretical data.

Ab initio lattice dynamics of Ni2MnX (X=Sn, Sb) magnetic shape memory alloys

“…The details of the calculation procedure and strain tensors used have been explained in detail in Refs. [18,19]. The phonon dispersion spectra are constructed by using DFPT in the linear response approach [20][21][22], in which second order derivatives of the total energy are calculated to obtain dynamical matrix.…”

First principles study of barium chalcogenides

“…All the details of elastic constant calculation procedure including strain tensors used were explained in detail in Refs. [20,21].…”

Structural analysis of partially covalent lanthanide and actinide bismuthides with phase‐transition pressures below 14 GPa

“…The pressure derivatives of bulk modulus have been compared with theoretical [25] and experimental data [5,22]. Due to lack of experimental data for SOECs, we have compared our results with theoretical data and we found that the values of SOECs are of the same order as reported by others [15][16][17]. To the best of our knowledge no experimental data of second-order elastic constants for these rare-earth pnictides have been reported as yet.…”

“…Our present values of SOECs are close to available theoretical data [15][16][17]. The pressure derivatives of bulk modulus have been compared with theoretical [25] and experimental data [5,22].…”