′�?, with a frequency of 295 cm−1, is attributed on the stretching vibration of Ga–Se bonds. The two-phonon absorption in the 295 cm−1 phonon corresponds to the crystal IR absorption edge, instead of the residual absorption peak. Density functional idea computations clearly show the residual absorption in the BGSe crystal https://archersjvht.dm-blog.com/32771186/detailed-notes-on-baga4se7-crystal