### The Solid State

goals
What is the crystallograph dimension of monoclinic unit cell?
In the given crystal what should be the cation $X$ which replaces to create a ${ Na }^{ + }$ cation vacancy?
For a given anion, the graph for NaCL type structure levels off at low ($r^+/r^-$) values because of ?
$Fe_3O_4$ is ?
Classification of crystalline solids?