Crystal Structures of Energetic Compounds: Ab-Initio Potential Functions and Ab-Initio Crystal Orbitals

Abstract

Detonation pressures and detonation velocities are governed by the crystal densities (gms./cc.) of explosives. Our approach to predicting optimal crystal-packing and crystal-structure parameters is based on ab-initio potential functions from nonempirical ab-initio calculations of smaller molecular aggregates (monomers, dimers, trimers, etc.). The total SCF interaction energies are partitioned into the different components, and then these components are fit individually to functional forms or when necessary recalculated or estimated explicitly for certain interaction components for each different unit cell dimension change. The CRYSTAL-JHU program, given the crystal symmetry, allows us to vary and optimize the crystal-structure parameters. The agreement of our calculated unit cell dimensions of nitromethane (CH3NO2) and of RDX with experiment was excellent, within 1 to 2.8%.