Effect of disorder on the optical properties of NaNO₂

Abstract

The band structure and the optical properties of NaNO₂ in the disordered paraelectric phase are studied by the self-consistent OLCAO method. Calculations are performed on several disordered models and the configurational average is taken. The results show that the effect of polarization reversal on the electronic structure is minimal. NaNO2 basically retains the insulating properties of the ferroelectric phase with a reduction in the band gap of only 0.3 eV. The optical calculation reveals a decrease in the optical anisotropy. The disorder also leads to a normal decrease in the dielectric function, showing the dielectric screening by electrons is weakened by disorder scattering.