Lattice Dynamics of LiH2PO4 Crystal

Lattice dynamics of hydrogen bonded representative of KH2PO4 crystal family, LiH2PO4, was investigated within the first principles density functional theory. Phonon dispersion relations along symmetry directions of Brillouin zone, density of phonon states, electron density maps and heat capacity were calculated. Experimental Raman spectra (Lee et al., 2008) are interpreted in detail based on eigen-vector analysis in Brillouin zone center. We come to the conclusion that the dynamically stable phonon spectrum and a tight electrostatic coupling between the Li ions and tetrahedrally coordinated oxygen ions are the main reasons for the crystal lattice stability and for the lack of ferroelectricity in LiH2PO4 crystal.