crystal structures

rock salt (type, cations anions, a)

FCC. 4 cations, 4 anions. a = 2Ra + 2 Rc

BCC (APF, cn, n, a, close packed)

0.68, 8, 2, 4/sqrt3(R), close packed along body diagonal [111]

interstitial site simple cubic, octahedral, tetrahedral (FCC)

in body centre. Cn = 8

among neighbouring host atoms, CN = 6

among neighboring host atoms, CN = 4

ideal interstitial site size for octahedral and simple cube, and coordination number

Octahedral 6 0.414, 4 sites in FCC

Simple Cubic 8 0.732

r/R = radius interstitial / radius host

HCP (c/a, V, n, CN, V, apf, a)

c/a = 1.633

V = 24sqrt2 r³

n = 6

CN = 12

v = 3sqrt3/2 a² c

apf = 0.74

a = 2r

slip planes

dislocations move on highest packing and closest packed directions
fcc slip planes {111}
each 111 plane has a 110 direction so 12 slip systems

ZnS

tetrahedral interstitial site

Cn = 4

fcc

CsCl

simple cube

n = 2

cn = 8

rc/ra = 0.732

close packed <111>

diamond crystal

n= 8 (4 external 4 internal)

CN = 4

tetrahedral

APF = 34%

r/R - 0.225 (tetrahedral)

zinc blend lattice parameter

4/sqrt3 (Ra + rc)