Collision cascade

For the scenario of collisions between objects in low earth orbit producing a chain reactions of debris colliding with additional objects producing more debris, see Kessler syndrome.
A classical molecular dynamics computer simulation of a collision cascade in Au induced by a 10 keV Au self-recoil. This is a typical case of a collision cascade in the heat spike regime. Each small sphere illustrates the position of an atom, in a 2-atom-layer-thick cross section of a three-dimensional simulation cell. The colors show (on a logarithmic scale) the kinetic energy of the atoms, with white and red being high kinetic energy from 10 keV downwards, and blue being low.

In condensed-matter physics, a collision cascade (also known as a displacement cascade or a displacement spike) is a set of nearby adjacent energetic (much higher than ordinary thermal energies) collisions of atoms induced by an energetic particle in a solid or liquid.[1][2]

If the maximum atom or ion energies in a collision cascade are higher than the threshold displacement energy of the material (tens of eVs or more), the collisions can permanently displace atoms from their lattice sites and produce defects. The initial energetic atom can be, e.g., an ion from a particle accelerator, an atomic recoil produced by a passing high-energy neutron, electron or photon, or be produced when a radioactive nucleus decays and gives the atom a recoil energy.

The nature of collision cascades can vary strongly depending on the energy and mass of the recoil/incoming ion and density of the material (stopping power).

  1. ^ R. S. Averback and T. Diaz de la Rubia (1998). "Displacement damage in irradiated metals and semiconductors". In H. Ehrenfest; F. Spaepen (eds.). Solid State Physics. Vol. 51. Academic Press. pp. 281–402.
  2. ^ R. Smith, ed. (1997). Atomic & ion collisions in solids and at surfaces: theory, simulation and applications. Cambridge University Press. ISBN 0-521-44022-X.