Page 59 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

E L E M E N T S I R-3.4

atom. This symbol defines the structure of the allotrope in terms of its Bravais lattice (crystal
class and type of unit cell, see Table IR-3.1) a nd the number of atoms in its unit cell. Thus,
iron(cF4) is the allotropic modification of iron ( g-iron) with a c ubic (c), all-face-centred ( F)
lattice containing four atoms of iron in the unit cell.

Table IR-3.1 Pearson symbols used for the fourteen Bravais lattices

System Lattice symbol a Pearson symbol

Triclinic P a P
Monoclinic P m P
S b mS
Orthorhombic P o P
S o S
F o F
I o I
Tetragonal P t P
I t I
Hexagonal (and trigonal P) P hP
Rhombohedral R h R
Cubic P c P
F c F
I c I

a
P, S, F, I and R are primitive, side-face-centred, all-face-centred, body-
centred and rhombohedral lattices, respectively. The letter C was formerly
used in place of S.
b
Second setting, y-axis unique.

Examples:

Symbol Systematic name Acceptable alternative name
1. P n phosphorus(oS8) black phosphorus
2. C n carbon(cF8) diamond
3. C n carbon(hP4) graphite (common form)
4. C n carbon(hR6) graphite (less common form)
5. Fe n iron(cI2) a-iron

6. Fe n iron(cF4) g-iron
7. Sn n tin(cF8) a- o r g rey tin
8. Sn n tin(tI4) b- o r w hite tin
9. Mn n manganese(cI58) a-manganese
10. Mn n manganese(cP20) b-manganese
11. Mn n manganese(cF4) g-manganese
12. Mn n manganese(cI2) d-manganese

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