Lattice parameters, deviations from Vegard’s rule, and $E2$ phonons in InAlN

The lattice parameters of $InxAl1−xN$ in the whole compositional range are studied using first-principle calculations. Deviations from Vegard’s rule are obtained via the bowing parameters, $δa=0.0412±0.0039Å$ and $δc=−0.060±0.010Å$⁠, which largely differ from previously reported values. Implications of the observed deviations from Vegard’s rule on the In content extracted from x-ray diffraction are discussed. We also combine these results with x-ray diffraction and Raman scattering studies on $InxAl1−xN$ nanocolumns with $0.627⩽x⩽1$ and determine the $E2$ phonon frequencies versus In composition in the scarcely studied In-rich compositional range.