The influence of core structure on dislocation mobility

A general theory is developed to account for the mobility of a dislocation which is sessile in its low-energy form. It is shown that three distinct mechanisms for movement are possible, each controlling the mobility over a different stress range. A specific core model is used to derive an expression for the mobility of screw dislocations in b.c.c. metals, and it is shown that the theory can account satisfactorily for the temperature and orientation dependence of the yield stress and slip geometry, and the stress dependence of the activation energy and volume in b.c.c. metals.