Numerical calculations were made of the concentrations of interstitials in hard-sphere crystals. It was found that, in a 3-dimensional face-centered cubic hard-sphere crystal at the melting point, the interstitial concentration was equal to 2.7 x 10-8. This value was about 3 orders of magnitude lower than the vacancy concentration.

Point Defects in Hard-Sphere Crystals. S.Pronk, D.Frenkel: Journal of Physical Chemistry B, 2001, 105[28], 6722-7