Electronic structure of CaX (X = O, S, Se) compounds using Compton spectroscopy

The electronic structure of CaO, CaS and CaSe through Compton spectroscopy is reported in this work. Both directional as well as spherically averaged Compton profiles are calculated for all the three compounds employing the CRYSTAL code within the framework of density functional theory (DFT). The anisotropy [1 0 0]–[1 1 0] for CaO is in agreement with the earlier values. The spherically averaged theoretical values are compared with the first ever measurement made on polycrystalline samples using 59.54 keV gamma-rays from Am241 source. The calculations are in good agreement with measurements in all cases. Charge transfer in the three compounds has also been estimated following the ionic model. The present study suggests charge transfer from Ca to X (O, S, Se) atom. On the basis of equal-valence-electron-density (EVED) profiles, it is found that CaO is more ionic compared to CaS and CaSe. From the DFT based calculations, we have also determined the cohesive energies, which are compared with other investigations.