- #1
fluidistic
Gold Member
- 3,923
- 260
Homework Statement
Knowing that sodium has a BCC structure, a density of 970 kg/m^3 and each atom has an atomic mass of 22.98 amu, determine the length of the primitive cell.
Homework Equations
Not sure.
The Attempt at a Solution
I calculated how many atoms of Na there is in 1m^3, namely around [itex]2.55 \times 10 ^{28}[/itex] atoms. But I have a huge problem. I know that each primitive cell contain 9 sodium atoms. The problem appears when I start with 1 primitive cell and I put another primitive cell close to the first one, I don't obtain 18 atoms but 9+9-4=14 atoms because both cells share 4 atoms.
I can imagine other configurations of primitive cells where adding another primitive cell only gives 1 more atom for example. So it all depends how in space the primitive cells are.
Thus I'm stuck at calculating how many atoms there are per primitive cells "in average" or something like that.
Has someone an idea on how to go further? Thanks in advance!