UNIT -1 CRYSTAL STRUCTURE
DESCRIPTIVE TYPE QUESTIONS
1. Explain the various types of defects observed in crystal structures. Also show that the
number of Frenkel defects in equilibrium at a given temperature is proportional to
(NNi)1/2, where N be number of atoms and Ni be the interstitial atoms.
2. Find the family of crystal directions represented by cube edges, face diagonals and body
diagonals of the unit cube. Give the number of members in each family.
3. Explain the following terms:
(a) Lattice, basis and crystal structre
(b) Lattice parameters
(c) Unit cell, primitive cell and non primitive cell
(d) Miller indices
4. Show that the number of Frenkel defects as well as the number of Schottky defects in
ionic crystal depends on temperature.
5. What are Bravais space lattices? Discuss the details of all crystal systems and Bravais
lattices.
SHORT ANSWER QUESTIONS
6. The lattice constant for a unit cell of silicon is 6.2 Å. The crystal plane cuts intercepts of
length 2a, 3b, 9c are primitive vector of unit cell. Calculate the interplanar spacing.
7. With a neat diagram show the following miller planes and directions Planes (213) and (1
Ῑ 1) Directions [011] and [132]
8. Find the miller indices of the direction common to the planes (1 1 1) and (1 1 0) in a
cubic system.
9. Draw unit cell for trigonal crystal system.
10. Find the family of crystal directions represented by cube edges, face diagonals and body
diagonals of the unit cube. Give the number of members in each family.
11. What is the relation between lattice parameter and density of cubic crystal system?
12. Define the term atomic packing fraction. Calculate atomic packing fraction for FCC
lattice.
13. Draw (111) plane in orthorhombic unit cell. Also draw [101] direction in tetragonal unit
cell.
14. Define crystal lattice, basis and crystal structure.
15. What are the Miller indices of the line of intersection of a (1̅1̅1) and a (1̅1̅1̅) plane in a
cubic crystal? Determine the answer both geometrically and analytically.
16. Draw (1 1 1) plane in a triclinic lattice and (1 2̅ 2) plane in a tetragonal lattice.
MCQs
17. The coordination number of BCC lattice is
(i)
1
(ii)
(iii) 4
2
(iv) 8
18. Which one of the following Bravais lattices is not found in cubic crystal?
(i)
Simple cubic
(ii)
(iii) Face centrered cubic
Body centered cubic
(iv) Base centrered cubic
19. In a simple cubic lattice the ratio d111:d112:d100 is
(i)
√6: √3: √2
(ii)
(iii) 6: 3: √2
√2: 1:√6
(iv) 6: 3: 1
20. The (1̅̅̅
1 1) plane is parallel to
(i)
(1 1 1)
(iii) (1̅ 1̅ 1)
(ii)
(1̅ 1 1̅ )
(iv) (1 1 1̅ )
21. If the radius of atom in a simple cubic crystal is r, the body diagonal of unit cell is
(i)
r (3)1/2
(iii) 4r/ (3)1/2
(ii)
2r (3)1/2
(iv) 3r/4
22. The unit cell with three lattice parameters is
(i)
tetragonal
(iii) monoclinic
(ii)
orthorhombic
(iv) Triclinic
23. The properties of materials are highly anisotropic when they are in the form of
(i)
Polycrystalline
(iii) Liquid
(ii)
Single crystalline
(iv) Amorphous
24. In which of the following materials there is long range order?
(i)
Amorphous material
(iii) Liquid
(ii)
Single crystal
(iv) Glassy matrial
25. The direction along the face diagonal of a cubic crystal is denoted by
(i)
[1 1 1]
(iii) [1 1 0]
(ii)
[1 0 0]
(iv) [1 1 2]
26. Which of the following materials normally exist(s) in amorphous forms?
(i)
Copper
(iii) Quartz
(ii)
Window glass
(iv) Sugar
27. Which of the following structures have the highest packing factor?
(i)
FCC
(iii) BCC
(ii)
Simple cubic
(iv) HCP
28. The coordination number in FCC structures is
(i)
4
(iii) 8
(ii)
6
(iv) 12
29. Among the following bonds which one is the weakest?
(i)
Covalent bond
(iii) Metallic bond
(ii)
Ionic bond
(iv) Van der Waals bond
30. A plane intercepts the crystal axes ‘a’ at 0.25a and ‘b’ at 0.50b. It is parallel to the third
axis. Then Miller indices of plane are
(i)
(2 2 4)
(iii) (1 0 2)
(ii)
(2 1 0)
(iv) (4 2 2)
31. How many atoms per unit cell are there in diamond cubic structure?
(i)
4
(iii) 8
(ii)
6
(iv) 12