Unformatted text preview: In general, a = 2 r (anion) + 2r (cation) For MgO there are four Mg ions and four O ions. a = 2 r O2-+ 2r Mg2+ = 2(1.40 + 0.72)A =4.24A density = 4 (24.31+16)g/(6.02x10 23 )(4.24x10-8 cm) 3 = 161.24/45.89 = 3.51 g/cm 3 3. For MgO, draw the (111) and (110) planes, identifying atoms and empty site locations. 4. ZrO 2 takes various crystal structures. At the highest temperature, it takes cubic; at intermediate temperature, tetragonal and at the low temperature, monoclinic structure. Sketch a schematic Gibbs free energy vs. temperature for all three structures. 5. Would polymer crystals be isotropic? No. They would be anisotropic....
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- Spring '08
- Ion, Fundamental physics concepts, Crystal system, lattice parameter, consequently lower density