Diffusion coefficient can be expressed by D=Ta6 for any diffusing species in any cubic lattice. Show that this is true for vacancy diffusion in a pure foc metal. (Hint: consider two adjacent {111} planes and determine what fraction of all possible jumps result in the transfer of a vacancy between the two planes. Is the same result obtained by considering adjacent (100) planes?) Diffusion coefficient can be expressed by D=Ta6 for any diffusing species in any cubic lattice. Show that this is true for vacancy diffusion in a pure foc metal. (Hint: consider two adjacent {111} planes and determine what fraction of all possible jumps result in the transfer of a vacancy between the two planes. Is the same result obtained by considering adjacent (100) planes?)