In a 1999 study of cobalt nanocrystals, D. P. Dinega and M. G. Bawendi discovered that cobalt forms an interesting cubic structure unlike any of the cubic structures described in this chapter. They called this new form -cobalt to distinguish it from the more commonly encountered hcp and fcc forms of cobalt. For e-cobalt, the unit cell has an edge length of 609.7 pm and contains 20 atoms. The density of -cobalt is ρ = 8.635 g cm^–3. Use these data to estimate the number of cobalt atoms in a spherical nanocrystal of P-cobalt if the diameter of the nanocrystal is 2 nm.