Energetic atom collisions in solids induce shockwaves with complex morphologies. In this paper, we establish the existence of a morphological transition in such cascades. The order parameter of the morphology is defined as the exponent, b, in the defect production curve as a function of cascade energy (NF ∼ E b M D ). Response of different bcc metals can be compared in a consistent energy domain when the energy is normalized by the transition energy, µ, between the high-and the low-energy regime. Using Cr, Fe, Mo and W data, an empirical formula of µ as a function of displacement threshold energy, E d , is presented for bcc metals.

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