Difference between Body centred and face centred cubic unit cell
Body centred cubic unit cell |
Face centred cubic unit cell |
1) In a body centred cubic unit cell, the molecules occupy corners as well as body centre . | In face-centred cubic unit cell, the molecule occupy corners as well as face centre. |
2) The body centred cubic unit structure has an atom at all 8 corners positions and another one at the center of the cube. | the face-centred cubic structure has an atom at all 8 corner position and at the center of all 6 faces. |
3) Coordination number of body-centred cubic unit cell is 68 percent. | coordination number of face-centred cubic unit cell has 12. |
4) Atomic packing factor in body centred cubic unit cell is 68 percent. | atomic packing factor in face-centred cubic unit cell has 12. |
5) Relationship between cube edge length a and atomic radius R is a= 4R/(3)^1/2 | relationsheep between cube edge length and atomic radius is a= 2R(2)^1/2 |
6) Closed-packed structure are absent in body-centred cubic unit cells. | face-centred cubic unit cell show closed-packing structure. |
7) There are 2 number of atom per unit cell. | there are 4 number of atom per unit cell. |
8) There are total six number of octahedral interstitial sites present in body centered cubic unit cells. | there are total four octahydral sites present in face-centred cubic unit cells. |
9) Number of tetrahedral interstitial sites is 12. | Number of tetrahydral interstitial sites is 8. |
10) Body centred cubic unit cell has less stable, less dense, less ductile than face centred cubic unit cells. | Face-centred cubic unit cell has more, dense, more stable and more ductile than body-centred unit cells. |
11) All body centred cubic unit cell have a ductile to brittle transition [DBTT] | Face-centred metal do not have a DBTT(Ductile-to brittle transmission tempreters) |
12) Tetrahydral sites bigger than octahedral. | Face-centred cubic slipdirection closed packing plane. |
13) Example: at room temperature lithium, sodium, potassium, chromium, iron.Mn, Rb. | Example: Al, Ca, Ni, Cu, Rh, Pd, Ag, Yb,P, Au. |