′�?, using a frequency of 295 cm−1, is attributed to your stretching vibration of Ga–Se bonds. The 2-phonon absorption of the 295 cm−one phonon corresponds to your crystal IR absorption edge, rather than the residual absorption peak. Density functional idea computations clearly show the residual absorption in the BGSe crystal https://martinbqfrd.shotblogs.com/not-known-factual-statements-about-baga4se7-crystal-46435210