Abstract Full-potential linearized augmented plane wave method has been used to study the cross luminescence of halide scintillators. The electronic structure and optical properties of alkali halides such as CsMgCl3, CsCaCl3, and CsSrCl3 are presented. One of the major criteria for the cross luminescence to happen is the energy difference between valence band and next deeper core valence band being lesser when compared to energy gap of the compound, so that radiative electronic transition may occur between core valence band and valence band which might lead to fast scintillation. We found this criterion to be satisfied in these compounds leading to cross luminescence. The presence of high energy peaks in the absorption spectra indicates the creation of holes in the core valence band, which is an essential criterion for the occurrence of cross luminescence. The electronic structure, and optical properties studies clearly indicate CsMgCl3, CsCaCl3, and CsSrCl3 to be cross luminescence materials comparable to CsCl which is one of the well known fast scintillators. In addition, CsMgCl3 is found to be better among the studied compounds with optical isotropy though the compound is structurally anisotropic. © 2015 Elsevier Inc. All rights reserved.