Generalized stacking fault energies in the basal plane of triclinic molecular crystal 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)

Abstract

Molecular dynamics and molecular statics simulations were used to investigate dislocation glide in the basal plane (i.e. the – plane, where , and define the edge vectors of the unit cell) of -triamino--trinitrobenzene (TATB) using generalized stacking fault energy surfaces (-surfaces). Triclinic symmetry and molecular packing arrangement result in two glide plane types for the same glide plane normal. The unstable stacking fault energies () are less than at K and atm, indicating easy dislocation glide. Glide in the and – directions is preferred compared to the direction at atm. A stable stacking fault is predicted in the – direction at atm and 5 GPa. A compound twin with energy is predicted to be stable in the basal plane. Unequal values of about the stable stacking fault in the and – traces indicate an asymmetric barrier to dislocation glide. High pressure ( GPa) results in an increase in the values. The extremely small barriers to twinning and dislocation glide might be sources for observed second-harmonic generation in the nominally centrosymmetric crystal.