Novel III-V Nitride Polymorphs in theP42/mnmandPbcaPhases

In this work, the elastic anisotropy, mechanical stability, and electronic properties forP4(2)/mnmXN (XN = BN, AlN, GaN, and InN) andPbcaXN are researched based on density functional theory. Here, the XN in theP4(2)/mnmandPbcaphases have a mechanic stability and dynamic stability. Compared with thePnmaphase andPm-3nphase, theP4(2)/mnmandPbcaphases have greater values of bulk modulus and shear modulus. The ratio of the bulk modulus (B), shear modulus (G), and Poisson's ratio (v) of XN in theP4(2)/mnmandPbcaphases are smaller than those forPnmaXN andPm-3nXN, and larger than those for c-XN, indicating thatPnmaXN andPm-3nXN are more ductile thanP4(2)/mnmXN andPbcaXN, and that c-XN is more brittle thanP4(2)/mnmXN andPbcaXN. In addition, in thePbcaphases, XN can be considered a semiconductor material, while in theP4(2)/mnmphase, GaN and InN have direct band-gap, and BN and AlN are indirect wide band gap materials. The novel III-V nitride polymorphs in theP4(2)/mnmandPbcaphases may have great potential for application in visible light detectors, ultraviolet detectors, infrared detectors, and light-emitting diodes.