Gain Spectrum for the In$\text{}_{4}$Se$\text{}_{3}$ Crystal with a Non-Standard Dispersion Law of Charge Carriers

Based upon the ab initio band structure calculations results and the density of states function of the orthorhombic In$\text{}_{4}$ Se$\text{}_{3}$ crystal as well as the experimental data concerning its radiative recombination, it was shown that the Bernard-Durafour condition is fulfilled for this crystal. The absorption coefficient α that exhibits a negative value in the given energy range and for the given concentrations of non-equilibrium charge carriers, was calculated.