Question:

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

Updated On: Apr 5, 2024
  • $ 39.27 \% $
  • $ 68.02 \% $
  • $ 74.05 \% $
  • $ 78.54 \% $
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The Correct Option is D

Solution and Explanation

Contribution of circle from comer of square $ = \frac{1}{4} $
$ \Rightarrow $ Effective number of circle per square
$ = \frac{1}{4} \times 4 + 1(at\, \, centre) = 2 $
$ \Rightarrow $ Area occupied by circle $ = 2 \pi r^2 , r = radius. $
Also, diagonal of square $ 4r = \sqrt 2 L, $ where L = side of square.
$ \Rightarrow $ Packing fraction $ = \frac{Area\, \, occupied\, \, by\, \, circles}{Area\, \, of\, \, square} $
$ = \frac{2 \pi r^2}{L^2} = \frac{2 \pi r^2}{8r^2} = \frac{\pi}{4} = 0.785 $
$ \Rightarrow \% Packing\, \, efficiency = 78.5 \% $
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Concepts Used:

Solid State

Solids are substances that are featured by a definite shape, volume, and high density. In the solid-state, the composed particles are arranged in several manners. Solid-state, in simple terms, means "no moving parts." Thus solid-state electronic devices are the ones inclusive of solid components that don’t change their position. Solid is a state of matter where the composed particles are arranged close to each other. The composed particles can be either atoms, molecules, or ions. 

Solid State

Types of Solids:

Based on the nature of the order that is present in the arrangement of their constituent particles solids can be divided into two types;

  • Amorphous solids behave the same as super cool liquids due to the arrangement of constituent particles in short-range order. They are isotropic and have a broad melting point (range is about greater than 5°C).
  • Crystalline solids have a fixed shape and the constituent particles are arranged in a long-range order.