1. Atoms per Cell — "SBF = 1-2-4"

• Simple Cubic = 1
• BCC = 2
• FCC = 4
• Alternative: "S(one), B(two), F(our)" — each step doubles

2. Schottky vs Frenkel — "Schottky Shrinks, Frenkel is Fixed"

• Schottky = Shrinks density (ion pairs leave)
• Frenkel = Fixed density (ion just moves inside)
• Schottky = Similar-sized ions
• Frenkel = Fat anion (large anion, small cation)
• AgBr = "AB exception" — shows both

3. Void Counting — "One-Oct, Two-Tet"

• For n atoms: 1×n octahedral, 2×n tetrahedral

4. Contact Direction — "SC-Edge, BCC-Body, FCC-Face"

• SC: atoms touch along Edge (a = 2r)
• BCC: atoms touch along Body diagonal (a√3 = 4r)
• FCC: atoms touch along Face diagonal (a√2 = 4r)

5. Coordination Numbers — "SC=6, BCC=8, FCC=12 = 6-8-12"

• SC: 1 atom on each of 6 faces = 6
• BCC: 8 corners touch body centre = 8
• FCC: closest → 12

6. Magnetic Types — "DPFAF"

• Diamagnetic → all paired, repelled
• Paramagnetic → unpaired, random, weakly attracted
• Ferromagnetic → domains aligned, strongly attracted
• Antiferromagnetic → antiparallel equal, cancel
• Ferrimagnetic → antiparallel unequal, net moment

7. Semiconductor Doping — "15=n, 13=p"

• Group 15 (5 valence $e^{-}$) → extra electron → n-type
• Group 13 (3 valence $e^{-}$) → missing electron → p-type