Vibrational and dielectric properties of magnesium aluminate spinel: A first-principles study

The vibrational and dielectric properties of MgAl2O4 are investigated within the framework of density functional perturbation theory. Results of phonon frequencies at the Brillouin zone center, static dielectric constant, and electronic dielectric constant are reported. In comparison with experimental results, we find that the generalized gradient approximation potential results in more accurate phonon frequencies than local density approximation potential does. Dielectric, refractive index, extinction coefficient and infrared reflectance spectra of MgAl2O4 are given, and the figures suggest that MgAl2O4 presents good transmission properties in the spectrum range above 1000 cm−11000 cm−1 and below 300 cm−1300 cm−1.

► MgAl2O4 has an electronic dielectric constant smaller than the lattice component.
► GGA potential results in more accurate phonon frequencies compared to LDA potential.
► Weak reflection peaks at 321 cm−1321 cm−1 and 596 cm−1596 cm−1 result in narrow LO-TO bands.
► Infrared spectrum suggests good transmission above 1000 cm−11000 cm−1 and below 300 cm−1300 cm−1.