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Unit cell dimensions
Concepts tested here
- Body-centred cubic structure
All Questions
2010 AIPMT-PRE 1 question
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AB crystallizes in a body centred cubic lattice with edge length 'a' equal to 387 pm. The distance between two oppositely charged ions in the lattice isIn a body-centred cubic (CsCl type) arrangement one kind of ion is at the corners and the oppositely charged ion is at the body centre.
The ions touch along the body diagonal, whose length is $\sqrt{3}a$.
The body diagonal contains corner ion – centre ion – corner ion: $2(r^+ + r^-) = \sqrt{3}a$
Distance between oppositely charged ions: $r^+ + r^- = \frac{\sqrt{3}a}{2} = \frac{1.732\times387}{2}$
$= 335.1$ pm $\approx 335$ pm