If we know the radii of the ions in a CsCl-like cell, we can estimate the cell dimension. Thallium(I) Chloride, TlCl, crystallizes with a CsCl-like structure. We estimate the the edge length of the unit cell from the published values of the radii:
The radius of Tl⁺ is 156 pm
The radius of Cl ^- is 181 pm

a = d/1.732
   = 674 pm/1.732
   = 389 pm

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