The packing efficiency of the two dimensional square unit cell shown below is:

Options

A. `39.27%`
B. `68.02 %`
C. `74.05%`
D. `78.54%`

Answer

D

Explanation

`asqrt(2)=4r` , `a=2sqrt(2)r`
packing fraction `=("Occupied area")/("Total area")xx100`
`=(2pir^(2))/((2sqrt(2)r)^(2))xx100=78.5%`