  In the present work we analyze some necessary conditions for ignition of
solid energetic materials by low velocity impact ignition mechanism. Basing on
reported results of {\it ab initio} computations we assume that the energetic
activation barriers for the primary endothermic dissociation in some energetic
materials may be locally lowered due to the effect of shear strain caused by
the impact. We show that the ignition may be initiated in regions with the
reduced activation barriers, even at moderately low exothermicity of the
subsequent exothermic reactions thus suggesting that the above regions may
serve as "hot spots" for the ignition. We apply our results to analyze initial
steps of ignition in DADNE and TATB molecular crystals.
