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Possible role of dispersion forces in fracture

Dispersion (London) forces act between any two solid bodies. These forces are small except when the bodies are close together. They decrease rapidly as the distance between the bodies increases. Near the tip of a crack one body separates into two, and the two pieces are close together for a short distance. Thus, dispersion forces may play a role in the behaviour of crack tips. They cannot change the intrinsic surface energy, but they can affect the tip's width, and therefore, the time needed (at a given velocity) to complete the separation process. This in turn may affect the time available for plastic deformation; and therefore the extrinsic fracture surface energy. This may be one reason that polarizability affects fracture. Also, it may relate to the correlation between fracture surface roughness and energy.