Optical band gap of the ordered filled-tetrahedral semiconductor LiMgP

The optical band gap (E-g) of the ordered filled-tetrahedral semiconductor LiMgP [viewed as a hypothetical zinc-blende (MgP)(-) lattice partially filled with He-like Li+ interstitials] was studied. X-ray diffraction studies of LiMgP show the antifluorite structure (space group F (4) over bar 3m) with the ordered arrangement between Li and Mg rather than the disordered structure reported previously. The band-gap of LiMgP is found to be direct, with a forbidden gap of 2.43 eV at room temperature as LiZnP predicted theoretically by an "interstitial insertion rule". As a result of the replacement of Zn by the light element Mg, the band-gap of LiMgP is larger than that of LiZnP (E-g similar to 2.04 eV). (C) 1998 Elsevier Science Ltd. All rights reserved.