Saved Bookmarks
| 1. |
Explain different types of unit cells. |
Answer» Solution : (a) Primitive unit cells : When constituent particles are present only on the corner POSITIONS of a unit cell, it is called as primitive unit cell.  (b) Centred Unit Cells : When a unit cell contains one or more constituent particles present at positions other than CORNERS in ADDITION to those at corners, it is called a centred unit cell. Centred unit cells are of three TYPES :(i) Body-Centred Unit Cells: Such a unit cell contains one constituent particle (atom, molecule or ion) at its bodycentre besides the ones that are at its corners. (ii) Face-Centred Unit Cells : Such a unit cell contains one constituent particle present at the centre of each face, besides the ones that are at its corners. (iii) End-Centred Unit Cells : In such a unit cell, one constituent particle is present at the centre of any two opposite faces besides the ones present at its corners.  There are seven types of primitive unit cells.  Unit cell of 14 types of Bravals Lattices: 
|
|