K.Parlinski, J.Lazewski and Y.Kawazoe,
Ab initio studies of phonons in MgO by the
direct method including LO mode,
J.Phys.Chem. Solids, 61, 87 (1999).
Crystal: Magnesium oxide MgO
Software: Ab initio Castep of MSI ver. 3.8
Space group: cubic, Fm-3m (O_h^5) (Z=1)
Lattice constants: a=4.216 angst.
Supercell: 2x2x2 and 1x1x16.
Pseudopotentials: high-precision of Castep
k-points: 1x1x1 and 3x3x1, respectively.
LO/TO splitting found in 1x1x16 supercell by
extrapolation of LO mode to k=0.
Phonon dispersion relations of MgO: