Modeling size and surface effects on ZnS phase selection

Transition temperatures between wurtzite and sphalerite polymorphs of ZnS nanoparticles and nanobelts are calculated by considering energetic contributions of surface energy, surface stress and external pressure on the total Gibbs free energy. It is found that the transition temperature between them drops as size of ZnS nanocrystals decreases, but increases with the increase of the external pressure. As results, wurtzite ZnS nanobelts could stably exist when their thickness is smaller than 10 nm at room temperature. The above results are consistent with available experimental results of ZnS nanoparticles and nanobelts.