Mumbai university > FE > SEM 1 > Applied Physics 1

Marks: 5M

Year: May 2015

Diamond is a metastable allotrope of carbonwhere the each carbon atom is bonded covalently with other surrounding four carbon atoms and are arranged in a variation of the face centered cubic crystal structure called a diamond lattice.

1) No. of atoms per unit cell-

Corner -1/8 × 8 = 1

Face -1/2 × 6 = 3

Four atoms - 4

Total = 8 atoms

2) Atomic radius-

$(XY)^2 = (XT)^2 + (YT)^2$

$ = (XT)^2 + (YZ)^2 + (TZ)^2$

$(2r)^2 = (\frac{a}{4})^2 + (\frac{a}{4})^2 + (\frac{a}{4})^2$

$ r = \frac{\sqrt{3}a}{8}$

3) Co-ordination no. is 4

Each carbon atom is in touch with 1 corner & 3 face centered atoms in a tetrahedral fashion, hence co-ordination no. is 4

4) Atomic packing factor $-\frac{v}{V} = 0.34 = 34$%