Find in Library

In this work, the elastic anisotropy, mechanical stability, and electronic properties for <i>P</i>4₂/<i>mnm</i> XN (XN = BN, AlN, GaN, and InN) and <i>Pbca</i> XN are researched based on density functional theory. Here, the XN in the <i>P</i>4₂/<i>mnm</i> and <i>Pbca</i> phases have a mechanic stability and dynamic stability. Compared with the <i>Pnma</i> phase and <i>Pm</i>-3<i>n</i> phase, the <i>P</i>4₂/<i>mnm</i> and <i>Pbca</i> phases have greater values of bulk modulus and shear modulus. The ratio of the bulk modulus (<i>B</i>), shear modulus (<i>G</i>), and Poisson’s ratio (<i>v</i>) of XN in the <i>P</i>4₂/<i>mnm</i> and <i>Pbca</i> phases are smaller than those for <i>Pnma</i> XN and <i>Pm</i>-3<i>n</i> XN, and larger than those for c-XN, indicating that <i>Pnma</i> XN and <i>Pm</i>-3<i>n</i> XN are more ductile than <i>P</i>4₂/<i>mnm</i> XN and <i>Pbca</i> XN, and that c-XN is more brittle than <i>P</i>4₂/<i>mnm</i> XN and <i>Pbca</i> XN. In addition, in the <i>Pbca</i> phases, XN can be considered a semiconductor material, while in the <i>P</i>4₂/<i>mnm</i> phase, GaN and InN have direct band-gap, and BN and AlN are indirect wide band gap materials. The novel III-V nitride polymorphs in the <i>P</i>4₂/<i>mnm</i> and <i>Pbca</i> phases may have great potential for application in visible light detectors, ultraviolet detectors, infrared detectors, and light-emitting diodes.