Threshold displacement energy

The threshold displacement energy is the minimum kinetic energy that an atom in a solid needs to be permanently displaced from its lattice site to a defect position. It is also known as "displacement threshold energy" or just "displacement energy". In a crystal, a separate threshold displacement energy exists for each crystallographic direction. Then one should distinguish between the minimum and average over all lattice directions threshold displacement energies. In amorphous solids it may be possible to define an effective displacement energy to describe some other average quantity of interest. Threshold displacement energies in typical solids are of the order of 10 - 50 eV.