STRUCTURAL AND ELECTRONIC-PROPERTIES OF ALKALINE-EARTH FLUOROHALIDES UNDER PRESSURE

The electronic band structure of the mixed alkaline-earth fluorohalide s-CaFCl, SrFCl, BaFCl, BaFBr, and BaFl in the PbFCl-type structure-wer e calculated using the tight-binding linear muffin-tin orbital method within the local-density approximation. The total energies calculated within the atomic sphere approximation were used to determine the grou nd-state properties of these systems. The calculated equilibrium latti ce parameters, cia ratio, the bulk modulus, and the pressure-volume re lation were found to be in good agreement with the experimental result s. The energy band-gap value at ambient conditions and the pressure de pendence of the band gap for these systems were also obtained. These s ystems are found to be direct band-gap insulators with the band gap in itially increasing with pressure which decreases upon further compress ion leading to band-overlap metallization at high pressures.