The interstitial point defect increases the density of a solid. Frenkel defect is also a type of this defect but it do not increases the density.

Also, the mass / volume concept of density tells us that density should be same in both cases, as they are basically interstitial defect. Then what happened to a covalent solid that density increased , and why it didn't happened to ionic solid?

(Please understand that it is not a duplicate of Why Frenkel defect does not impact the density of the solid? )

  • $\begingroup$ In the standard Fresnel case, the small ion is displaced. It fits easily in a position between the larger ions without disturbing them much, if at all. For other materials and structures that may not be the case. $\endgroup$
    – Jon Custer
    May 20, 2022 at 13:20
  • $\begingroup$ Does that means that in an interstitial defect in covalent solids , the particle in void disturbed other particles due to greater size? Is this is the only reason for differeneces of observed density? thank you $\endgroup$ May 21, 2022 at 6:46


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