Answer Happy

3. (a) State the Laue equations and define all the symbols used. (20 marks) (b)Derive the reciprocal lattice vectors for the primitive unit cells of face centered cell unit, fcc lattice. Calculate the volume of the corresponding reciprocal cell. (20 marks) (c)The geometrical structure factor, F is given by the following equation: F = fme-GoPm m where m = all atoms in a unit cell fm = atomic scattering factor of m'h atom Pm = relative position of the mth atom G = reciprocal lattice vector (0) Obtain the diffraction conditons for the planes in a body centered cubic, bcc lattice and state the first three planes with the largest interplanar distance. (30 marks) (ii) Tungsten, W has the bcc structure and a conventional unit cell parameter of 3.165 A. If copper Ka radiation is used (1 = 1.542 Å), calculate the Bragg angles for the planes in (i) (30 marks)