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Unformatted text preview: cause of theelectrons that are contained
core electrons Those nature of the coulombic attractive force,
we expect each Cs cation to be surrounded by as many negatively charged Cl anions
within the ﬁlled inner shells of system is minimized when the
as is geometrically possible. The total energy for the an atom.
number of oppositely charged nearest neighbors for each ion is maximized. The geometric
coring Variation in the solute distribution of a single
factor responsible for determining the CN of ions is the ratio of the radii of the ions.
phase due to nonequilibrium equilibrium separation distance for
Using the procedure outlined in Section 2.4.1, the solidiﬁcation. Coring occurs
CsCl, x0 (CsCl), can be foundcomposition of the solid is thenthe liquid are
because the from the bondenergy curve. It and possible to write
rC
x CsCl
(2.6–1)
r Clnot thes same0 at a speciﬁc temperature.
where the terms on the left are the radii ofA degradation mechanismwritten for
the ions. Similar equations may be in which
corrosion fatigue
a variety of compounds, and the resulting set of simultaneous equations may be solved for
corrosion and mechanical fatigue occur simultaneously
the respective radii. Using this procedure, a selfconsistent set of ionic radii can be
and their synergistic rigid sphere model for more serious than
calculated. The result justiﬁes the use of aeffects are much describing ionic solids.
The atomic and ionic radiipredicted from given inseparate C.
would be of the elements are their Appendix effects.
Let r represent the radius of the smaller ion, usually the cation, and let R represent the
Name given between the ratio of the force
radius of the coulombic forceanion. The relationshipto the electrostaticradii
larger ion, usually the
and the resulting CN can be determined using the following constraints: (1) cations of
that develops between charged species. The magnitude
“touch” anions, (2) the number of anions surrounding a given cation will be as high as
the force is proportional overlap.
geometrically...
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 Spring '10
 sowell
 Physics, The Crucible

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