′�?, that has a frequency of 295 cm−1, is attributed to your stretching vibration of Ga–Se bonds. The 2-phonon absorption with the 295 cm−1 phonon corresponds to your crystal IR absorption edge, rather than the residual absorption peak. Density purposeful principle computations show the residual absorption of the BGSe crystal https://baga4se7-crystal52839.popup-blog.com/31984576/everything-about-baga4se7-crystal