Ab initio simulation of defects in energetic materials. Part I. Molecular vacancy structure in RDX crystal

An attempt to simulate a point defect in energetic molecular solids and to find out its effect on the crystal electronic properties at the ab initio H artree-Fock level using two different solid-state models was performed. As an example, we have considered a molecular vacancy in RDX crystal. in the p eriodic and in the molecular cluster model. Low formation energy characteri zes this defect in the solid RDX indicating that a significant number of va cancies should be present in the crystal even at low temperatures. Narrowin g of fundamental gap (about 1 eV) is caused by the presence of vacancies in the material. The obtained results demonstrate anisotropy of the RDX cryst al with respect to the vacancy distribution. Trends received in periodic an d molecular cluster models agree well. (C) 1999 Elsevier Science Ltd. All r ights reserved.