Electronic structure of Ge3N4 possible structures

Experiments have shown that Ge3N4 is a promising material for application i n photodiodes, amplifiers, optic fibers, protective coatings, etc., and sev eral experimental studies have been carried out on this material, however, only one theoretical study has been reported in the literature about beta-G e3N4. In this work we present a systematic study of the structural properti es and electronic structure of five possible structures of Ge3N4. The phase s under study are the alpha, beta, cubic, pseudocubic, and graphitic. The a nalysis shows that the hardest is the cubic with a bulk modulus B = 232.5 G Pa, while the alpha and beta have the same bulk modulus (B = 219.8 GPa). Th e pseudocubic and graphitic phases are the softest with B = 147.0 and 61.7 GPa, respectively. The band structure shows that the alpha, beta, cubic, an d pseudocubic have an indirect band gap while the graphitic has a direct ba nd gap. Total energy considerations indicate that the beta phase is the mos t stable while the graphitic is the less stable one. Charge density analysi s is also included. (C) 2000 John Wiley & Sons, Inc.