Editing Diamond (section)

=== Crystal structure ===
{{See also|Crystallographic defects in diamond}}
[[File:Diamond structure.gif|thumb|Diamond unit cell, showing the tetrahedral structure]]
The most common crystal structure of diamond is called [[diamond cubic]]. It is formed of [[unit cell]]s (see the figure) stacked together. Although there are 18 atoms in the figure, each corner atom is shared by eight unit cells and each atom in the center of a face is shared by two, so there are a total of eight atoms per unit cell.<ref>{{cite book | vauthors = Rajendran V |title=Materials science |date=2004 |publisher=Tata McGraw-Hill Pub |isbn=978-0-07-058369-6 |page=2.16}}</ref> The length of each side of the unit cell is denoted by ''a'' and is 3.567&nbsp;[[angstrom]]s.<ref name=Ashcroft>{{cite book | vauthors = Ashcroft NW, Mermin ND |title=Solid state physics |date=1976 |publisher=Holt, Rinehart and Winston |isbn=978-0-03-083993-1 |page=[https://archive.org/details/solidstatephysic00ashc/page/76 76] |url-access=registration |url=https://archive.org/details/solidstatephysic00ashc/page/76 }}</ref>

The nearest neighbor distance in the diamond lattice is 1.732''a''/4 where ''a'' is the lattice constant, usually given in Angstrøms as ''a'' = 3.567&nbsp;Å, which is 0.3567&nbsp;nm.

A diamond cubic lattice can be thought of as two interpenetrating [[face-centered cubic]] lattices with one displaced by {{frac|1|4}} of the diagonal along a cubic cell, or as one lattice with two atoms associated with each lattice point.<ref name=Ashcroft/> Viewed from a {{math|&lt;1 1 1&gt;}} [[Miller index|crystallographic direction]], it is formed of layers stacked in a repeating ABCABC ... pattern. Diamonds can also form an ABAB ... structure, which is known as hexagonal diamond or [[lonsdaleite]], but this is far less common and is formed under different conditions from cubic carbon.<ref>{{cite book |chapter=Molecular models of porous carbons| vauthors = Bandosz TJ, Biggs MJ, Gubbins KE, Hattori Y, Iiyama T, Kaneko T, Pikunic J, Thomson K | veditors = Radovic LR |title=Chemistry and physics of carbon |volume=28 |date=2003 |publisher=Marcel Dekker |isbn=978-0-8247-0987-7 |pages=46–47}}</ref>