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I.3 Visualizing the basic typsof crystal structures
Basic types:
Octahedral Holes
FCC:
Rocksalt
All filled with
cations
Antifluorite
HCP:
Wurtzite
Rutile
Perovskite:
FCC unit with A in
corners and O in
faces
Spinel:
FCC
1/2
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Simultaneous Equilibria
Modern cars have fuel injection systems that control the air/fuel ratio combusted. The
optimum ratio is 14.5. Above this ratio, hydrocarbons and carbon monoxide are
efficiently decomposed. Below it NO
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Radial Distribution Function
At this point, you have seen many different crystal structures. Close packing
considerations, stochiometry, and Paulings rules have shed light into why different
crystals are packed in different
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Origin of a Potential Energy Surface
The idea of a potential energy surface describing how atoms interact comes from an
approximation of the Schrdinguer equation made by Born and Oppenheimer. The
Schrdinguer equation can be
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I.2 Paulings rules provide empirical guidelines for understanding the stability of
ionic crystal structures
The main forces in an ionic crystal are coulombic interactions (both attractive and
repulsive) and repulsions due to
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Line and Planar Defects
A dislocation in a crystal is a displacement. Normally, these are formed during growth as
a result of accidents. They still maintain the electrostatic neutrality of the crystal. The
two most basic typ
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Mass and Electrical Transport
Electrochemical Potential and Devices
We just considered mobility due to chemical and electrical potential gradients. Normally
both are present at the same time even in the absence of an applied
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Mass and Electrical Transport
Electrical Conductivity
Ceramics exhibit a wide range of conductivities mostly though ionic conduction. To
understand how this is possible, it is helpful to first understand how the mobility of
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Mass and Electrical Transport
To consider mass and electrical transport through a material, it is helpful to have an
understanding of diffusion first at a continuum level i.e. without atomic details. After
this, well introdu
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Atomic level detail and the diffusion constant
Now, lets introduce some atomic level details to get a sense of what diffusion
coefficients mean. Consider atoms in the lattice shown in Figure 3.4. Notice that there is
a conce
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Defects in Ceramics
In the previous units, we have investigated the primary structural motifs and symmetries
in ceramics. We learned how to use Paulings rules to predict how interstitial sites are
filled. This led to a varie
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I.1 Closed-packed lattices are the basic skeletons
Most ceramics have structure based on closest packing of one constituent. The basic two
types of closest packing are face-centered cubic (FCC) and hexagonal closest packed
(