HW 3
HW 3
HW 3
Homework 3
Due to October 15th 2010, Friday 9:40 in class
1) Interplanar separation. Consider a plane hkl in a crystal lattice. (a) Prove that the
reciprocal lattice vector G = hb1 + kb2 + lb3 is perpendicular to this plane. (b) Prove that
the distance between two adjacent parallel planes of the lattice is d (hkl ) = 2π / G (c)
Show for a simple cubic lattice that d 2 = a 2 / (h 2 + k 2 + l 2 ) .
2) Hexagonal structure: Using the primitive vectors of the hexagonal space lattice
3a a
a1 = xˆ + yˆ ;
2 2
3a a
a2 = − xˆ + yˆ ;
2 2
a3 = czˆ
(a) Show that the volume of the primitive cell is ( 3 / 2)a 2 c .
(b) Find the primitive translation vectors of the reciprocal lattice and show that the
reciprocal of the simple hexagonal Bravais lattice also simple hexagonal, with
lattice constants 2π / c and 4π / 3a , rotated through 30o about c-axis with
respect to the direct lattice.
(c) For what value of c/a does the ratio have the same value both in direct and
reciprocal lattice? If c/a is ideal in direct lattice, what is its value in the reciprocal
lattice?