Nitromethane(NM,CH3NO2)is one of the simplest organic nitro compound and also a momentous energetic material.The C–N activation is the key step of nitromethane(NM)decomposition.The energy landscape of C–N rupture under applied electric fields with various directions and strengths were firstly studied by using CCSD and CCSD(T)calculations.When the field is applied in the C→ N direction,the activation energy barrier(Ea)increases under a weak field,but decreases when the field is strong enough.