Atomic Displacement Cross Sections in Copper for Anisotropic Threshold Energy

Earlier theoretical investigations on models of α‐iron [3] and copper [7] give a highly anisotropic displacement threshold energy, especially near the main crystal axes. In this paper total cross sections for atomic displacements by low energy electrons (E < 0.5 Me V) are calculated with respect to various anisotropic threshold energies. In general, a minimum of the threshold energy near a crystal axis leads to “sub‐threshold” events, as found experimentally by Bauer and Sosin. The cross sections derived from experimental measurements have to be corrected to take account of the effect of the energy loss and the multiple scattering of the electrons before they may be compared with calculated values. The correction method is described and the values from the Bauer and Sosin experiment given. By fitting the experimental data, the angular‐dependent threshold energy is calculated near the 〈110〉‐direction in copper assuming the residual resistivity increase to be 2.5 μΩ cm/at.% Frenkel pairs. The threshold energy minimum obtained by this method should be important as regards the production of correlated replacement collisions.