Comment on “DFT investigation of structural, electronic and optical properties of pure and Er-doped ZnO: Modified Becke-Johnson exchange potential”

Recently, Alkahtani et al. [1] studied the structural, electronic and optical properties of pure ZnO and Er-doped ZnO using generalized gradient approximation plus modified Becke-Johnson exchange potential. They doped erbium (Er) atom to ZnO zinc-blende structure. They did not perform spin polarized calculations, so their obtained electronic and optical properties are wrong. Also, the intra-band transition has not been considered in the their optical investigations. The correct form of these properties is presented and discussed in this paper.