) Derive linear density expressions for FCC [100] and [111] directions in terms of the atomic radius R. (b) Compute and compare linear density values for these same two directions for silver. 14. (a) Derive linear density expressions for BCC [100] and [111] directions in terms of the atomic radius R. (b) Compute and compare linear density values for these same two directions for tungsten. 15. (a) Derive planar density expressions for FCC (100) and (111) planes in terms of the atomic radius R. (b) Compute and compare planar density values for these same two planes for nickel. 16. (a) Derive planar density expressions for BCC (100) and (110) planes in terms of the atomic radius R. (b) Compute and compare planar density values for these same two planes for vanadium.