I have a small question about the density shown in Materials Studio. When I have a 3D atomistic structure, MS shows me the density of the structure at the box left handside below. I wanted to check if I would obtain the same number when I divide the mass of the structure with its volume. For example, for ZIF-8, the formula MS gives for the unit cell is C96H120N48Zn12, so the sum of the masses of the atoms in the unit cell is 2730.98 a.m.u, and the volume of the unit cell is 4904.39 A^3. When I divide this mass to volume and correct the units, I find 0.9246 g/cm^3, but MS shows 0.9655 g/cm^3.  Do you see what is my mistake here?
Thank you,