Summary of the 4

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	sc	bcc	fcc	hcp
Unit cell
Constants	$a$	$a$	$a$	$a, c$ (where $c > a$ )
With atom radius	$a=2r$	$a=\frac{4}{\sqrt{3}}r$	$a=\frac{4}{\sqrt{2}}r$	$a = 2r ; c=\sqrt{\frac{8}{3}}a$
Volume	$a^3$	$a^3$	$a^3$	$\frac{3}{2} \sqrt{3} a^2c$
Atoms per unit cell	1	2	4	6
Composition	$8\cdot\frac{1}{8}$	$8\cdot\frac{1}{8}+1$	$8\cdot\frac{1}{8}+6\cdot\frac{1}{2}$	$3+12\cdot\frac{1}{6}+2\cdot\frac{1}{2}$
Near-neigbour distance	$a$	$\frac{\sqrt{3}a}{2}$	$\frac{a}{\sqrt{2}}$	$a$
Coordination number	6	8	12	12
Coordination number	6	8	12	12
APF	52.36%	68%	74%	74%
Examples	Po	Fe, Cr, W	Al, Cu, Ni	Mg, Zn

Sources of the images:

Simple cubic: Original file @ Wikipedia
Body-centered cubic: Original file @ Wikipedia
Face-centered cubic: Original file @ Wikipedia
Hexagonal close-packed
By Original: Dornelf Vector: DePiep - Own work based on: Hexagonal close packed.png , CC BY-SA 3.0 ,Link

Written by

Sahithyan K.

September 29, 2026 2 min read

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