Shear-induced metallization of triamino-trinitrobenzene crystals

I report first principle density-functional calculations that demonstrate an insulator-metal transition based on the bending of covalent bonds in 1,3,5-triamino-2,4,6-trinitrobenzene, an organic molecular crystal. The critical shear angle responsible for the vanishing of the energy band gap is achieved at near constant volume via a 55° bending of the nitro group out of the molecular plane, accompanied by 0.1 Å stretch in the N–O bonds. The energy needed for inducing this motion is of the same order of magnitude as the energy band gap.