Structural and thermodynamic properties of wurtzite-type aluminium nitride from first-principles calculations

The lattice parameter, bulk modulus and its pressure derivative ofthe wurtzite-type aluminium nitride (w-AlN) are investigated by usingthe Cambridge Serial Total Energy Package (CASTEP) program in theframework of Density Functional Theory (DFT). The calculated resultsare in good agreement with the available experimental data and other theoretical results.Through the quasi-harmonic Debye model, the dependences of thenormalized lattice parameters $a/a_{0}$ and $ c/c_{0}$, axial ratio$c/a$, normalized primitive-cell volume $V/V_{0}$, Debyetemperature ${itTheta} _{rm D} $ and heat capacity $C_{rm V}$ onpressure $P $ and temperature $ T$ are obtained. It is found that theinterlayer covalent interactions (Al-N bonds) are more (even alittle) sensitive to temperature and pressure than intralayer ones(N--N bonds), which gives rise to a little lattice anisotropy in thew-AlN.