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.

Keywords:

• TATB
• stacking fault energy
• molecular crystal
• triclinic
• twins

Acknowledgements

The authors wish to thank Matt Kroonblawd for useful discussions. The authors also thank the anonymous reviewers for highly insightful comments.

Additional information

Funding

This work was supported by the US Air Force Office of Scientific Research [grant number FA9550-14-1-0091], [grant number 4731-UM-AFOSR-0002].