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Problem 4: The energy difference between \"hard\" (centered at H) and \"easy\" (centered at E; and E, ) core structures of screw dislocations in BCC Mo has been estimated to be 0.08 eV/b by density functional theory (DFT) calculations (Here b is the magnitude of its Burgers vector). Assuming that the screw dislocation must go through the \"hard\" core structure as it moves from one \"easy\" core structure centered at E; to the next at E,, estimate the critical stress required to move the screw dislocation at zero temperature (i.e. the Peierls stress). Assume the core energy varies with the dislocation center position as a simple sinusoidal function, and the lattice constant of Mo is a =3.147 A. The distance between two \"easy\" core centers E; and B, is [-[112]| = La. A, g D