Multiscale shock technique (MSST) has been shown to accurately reproduce the thermodynamic and chemical reaction paths throughout the shock wave fronts and reaction zone of shock initiation of energetic materials. A 1:1 cocrystal of hexanitrohexaazaisowurtzitane/trinitrotoluene (CL20/TNT) is shocked along the 110 orientations under the conditions of shock velocities lying in the range 610 kms-1 in ReaxFF molecular dynamics simulations. Products recognition analysis leads to reactions occurring with shock velocities of 7 kms-1 or stronger, and the shock initiation pressure is 24.56 GPa obtained from the conservation of Rankine-Hugoniot relation. Comparisons of the relationships are carried out between shock velocity and particle velocity, shock velocities and elastic-plastic transition. During shock initiation with the shock velocities lying in the range 78 kms-1, the shocked systems correspond to an elastic-plastic deformation, primary chemical reactions, and secondary chemical reactions. And the elastic-plastic transition coincides with the chemical reaction at higher shock velocity (9 kms-1), the cocrystal material response is over-driven, and all the thermodynamic properties show steep gradients, the compressed material by the shock wave steps into the plastic region, and a large number of carbon atoms appear in the early stage of over-driven shock initiation.