Thermally induced wurtzite to h-BN structural transition

Wurtzite (WZ) and hexagonal boron nitride (h-BN) are closely related crystal structures, both of which belong to the hexagonal crystal family. However, the WZ structure is commonly found in binary compounds such as ZnO and CdS, whereas crystals having a h-BN structure are very rare. In this study, a WZ$\to$h-BN structural transition is predicted to take place at high temperatures using molecular dynamic simulations with a generic pair potential model. This transition is entropically driven, whereby cations in crystal show extremely high mobility and are able to jump between nearby lattice sites when the temperature is higher than the critical point. Density function theory calculations for 14 AB compounds show that ZnO is the best candidate material that will undergo the WZ$\to$h-BN transition at high temperatures. This study predicts a new ferroelectric-paraelectric phase transition in WZ crystals that will change the materials' physical properties such as piezoelectricity and pyroelectricity. (© 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)