A New Phase of GaN

Abstract EN

The structural, mechanical, and electronic properties of the orthorhombic GaN (Pnma-GaN) are investigated at ambient pressure by using first-principles calculations method with the ultrasoft pseudopotential scheme.

The elastic constants and phonon calculations reveal Pnma-GaN is mechanically and dynamically stable at ambient pressure.

The calculated Young modulus of Pnma-GaN is 170 GPa, which is the three-fifths of wurtzite-GaN.

Electronic structure study shows that Pnma-GaN is a direct semiconductor with band gap of 1.847 eV.

The anisotropic calculation shows that wurtzite-GaN has a smaller elastic anisotropy than that of Pnma-GaN in Young’s modulus.

In addition, when the composition of aluminum increases from 0 to 0.063 in the alloy, the band gap decreases initially and increases afterward for Pnma-Ga1−xAl xN, while, for wurtzite-Ga1−x Al xN, the band gap increases with the increasing composition x.

Due to the structural porous feature, Pnma-GaN can also be expected to be a good hydrogen storage material.