CHE 163
HW CH#12 SOLIDS
04, 10, 12, 14, 16, 24, 28, 32, 34, 38, 42, 46, 50, 54, 56, 58, 60, 86, 90, 94, 96, 112, 114.
12-04
Because 8 A ions occupy the corners, and because the portion of the unit cell contains of each corner ion,
the number of A cations in the unit cell are
8 A cations = 1 A cation in the unit cell
Because 6 B ions occupy the faces, and because the portion of the unit cell contains 1
2 of each face ion, the
number of B cations in the unit cell are
6 B cations = 3 B cations in the unit cell
Because 1 X ions occupy the center, and because the unit cell contains 1 of each center ion, the number of X
anions in the unit cell is
1 X anions 1 = 1 X anion in the unit cell
This gives a total of one anion and four cations per unit cell.
12-10
12-12
12-14
Simplecubiccellsfeaturearepeatingarrangementofsquare-packedlayersdirectlyoveroneanother,inthe
pattern aaa… Overall, there is one particle contained in the volume of the unit cell, and the packing efficiency is52%.
Body-centeredcubiccellsfeaturearepeatingarrangementofsquare-packedlayersoffsetwithrespecttoeach other,inthepatternababab…Overall,therearetwoparticlescontainedinthevolumeoftheunitcell,andthe packingefficiencyis 68%.
Face-centeredcubiccellsfeaturearepeatingarrangementofclose-packedlayers,staggeredsuchthattherepeatingpatternisabcabc…Overall,therearefourparticlescontainedinthevolumeoftheunitcell,andthe packingefficiencyis 74%.
The unit cells, in order of decreasing packing efficiencyare:
face-centered cubic > body-centered cubic > simplecubic
12-16
From Figure 12.10 we can see that the packing in the bcc unit cell is less dense (more open spaces) than inthe
fcc unit cell. Therefore, the fcc unit cell has greater packingefficiency.
12-24
12-28
12-32
The disruption of the gold lattice by the smaller Ni atoms in white gold restricts the gold atoms fromslipping
past each other as easily as in pure gold. Therefore, pure gold is moremalleable.
12-34
The radius ratio of these alloys fall in therange
These ratios are significantly smaller than the 0.85 or higher ratio for substitutional alloys. Therefore, the large difference in atomic sizes accounts for the alloying elements occupying interstitial rather than substitutional latticesites.
12-38
12-42
12-46
12-50
12-54
In order of increasing band gap: conductor < semiconductor <insulator.
12-56
Because germanium holds its electrons less tightly, as indicated by its lower ionization energy, its presence in
silicon might enhance the electrical conductivity of silicon.
12-58
Extra electrons would be brought to the structure by doping in a halogen (group 17), which would bring seven
valence electrons to the structure of the semiconductor.
12-60
(a)Because boron has one fewer valence electron than carbon, the B-doped diamond is an example of a p-typesemiconductor.
12-86
12-90
12-94
12-96
12-112
12-114