New boron nitride structures B4N4: a first-principles random searching application.

The present investigation searched for new boron nitride (BN) polymorphs by means of first-principles simulations. The ab initio random structure searching strategy was implemented. The electronic and mechanical properties and equation of states of three new metastable BN crystal forms with equilibrium energies close to the most stable B4N4 form, c-BN, are presented. Results show either dynamically stable semiconductors or insulators, one of which is even slightly harder than c-BN. The equation of states is also presented and a phase transition is predicted.