paper

First-principle study of paraelectric and ferroelectric CsH $_{2}$ PO $_{4}$ including dispersion forces: stability and related vibrational, dielectric and elastic properties

arXiv:1801.08756 · doi:10.1103/PhysRevB.95.024112

Abstract

Using density functional theory (DFT) and density functional perturbation theory (DFPT), we investigate the stability and response functions of CsH $_{2}$ PO $_{4}$ , a ferroelectric material at low temperature. This material cannot be described properly by the usual (semi-)local approximations within DFT. The long-range e $^{-}$ -e $^{-}$ correlation needs to be properly taken into account, using, for instance, Grimme's DFT-D methods, as investigated in this work. We find that DFT-D3(BJ) performs the best for the members of the dihydrogenated alkali phosphate family (KH $_{2}$ PO $_{4}$ , RbH $_{2}$ PO $_{4}$ , CsH $_{2}$ PO $_{4}$ ), leading to experimental lattice parameters reproduced with an average deviation of 0.5 %. With these DFT-D methods, the structural, dielectric, vibrational and mechanical properties of CsH $_{2}$ PO $_{4}$ are globally in excellent agreement with the available experiments ( $<$ 2% MAPE for Raman-active phonons). Our study suggests the possible existence of a new low-temperature phase for CsH $_{2}$ PO $_{4}$ , not yet reported experimentally. Finally, we report the implementation of DFT-D contributions to elastic constants within DFPT.

This paper was published in Physical Review B the 25 January 2017 (21 pages, 4 figures)

First-principle study of paraelectric and ferroelectric CsH2​PO4​ including dispersion forces: stability and related vibrational, dielectric and elastic properties

Abstract

First-principle study of paraelectric and ferroelectric CsH $_{2}$ PO $_{4}$ including dispersion forces: stability and related vibrational, dielectric and elastic properties