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2.5 Complex structures

Intermetallics- Hume-Rothery-phases

Trend 1:

Intermetallics with a defined relation between structure and VEC

(Valence Electron Concentration)

Number (N) of valence electrons (empirical rules):

0: Fe, Co, Ni, Pt, Pd; 1: Cu, Ag, Au
2: Be, Mg, Zn, Cd; 3: Al; 4: Si, Ge, Sn; 5: Sb

VEC = N(val. electr) / N(atoms) (both per formula unit)

VEC 3/2 3/2 3/2 21/13 7/4

Structure CuZn -Mn HCP -Brass HCP

Example Cu Al Cu Si Cu Ga Cu Zn 8 CuZn 3
5
5
3
3
CoAl Ag Al Ag In Cu Al Cu Sn
3 3 9 4 3
NiIn CoZn 3 Au Sn Cu Si 8 Ag Sn
3
5
31