Flash Summary

Unit cells: SC (Z=1, CN=6, 52.4%), BCC (Z=2, CN=8, 68%), FCC (Z=4, CN=12, 74%). Density by ρ = ZM/( $a^{3}$ Nₐ); 1 Å = 10^{-8} cm.
Voids: n atoms → n octahedral (ratio 0.414) + 2n tetrahedral (ratio 0.225); NaCl fills all octahedral (6:6); ZnS fills half tetrahedral (4:4); CsCl is 8:8.
Defects: Schottky → density decreases; Frenkel → density unchanged; AgBr shows both. F-centres → coloured crystals, n-type. FeO → metal deficiency, p-type.
Semiconductors: Group 15 → n-type (electrons); Group 13 → p-type (holes). Conductivity increases with T (opposite to metals).
Magnetic: Fe/Co/Ni = ferromagnetic; MnO = antiferromagnetic; $Fe_{3}O_{4}$ = ferrimagnetic; $O_{2}$ = paramagnetic; NaCl = diamagnetic.