[Pw_forum] Confused on nat definition

[Luke Thulin]

Hello,

This may seem silly, but I'm confused as to what exactly the number of 
atoms in a unit cell is (nat).  For example, the Silicon example says 
that nat is only two, yet a diamond structure such as this should have 
much more than two atoms per unit cell.  Is the definition of nat the 
number of basis vectors?