4. Summary Structure ao vs r Atoms Coordination Packing Examples per cell Number factor Polonium SC ao=2r 6 0.52 (Po), a-Mn 4 Fe.Ti.W Mo BCC 2 8 0.68 Nb, Ta, K,Na VZr. cr 4 FCC 4 12 0.74 Fe, Cu, Au, Pt Ag, Pb, Ni HCP 0.74Ti, Mg Zn, Be Co≈1.633a Co Zr. CdStructure a0 vs. r Atoms per cell Coordination Number Packing factor Examples SC 1 6 0.52 Polonium (Po),α-Mn BCC 2 8 0.68 Fe,Ti,W,Mo, Nb,Ta,K,Na, V,Zr,Cr FCC 4 12 0.74 Fe,Cu,Au,Pt ,Ag,Pb,Ni HCP 2 12 0.74 Ti,Mg,Zn,Be ,Co,Zr,Cd a 2r 0 = a r 3 4 0 = a r 2 4 0 = 0 0 0 1.633 2 c a a r  = 4. Summary