Wrong hamiltonian for myqlm

I think there's a discrepancy between pulser and myqlm. 
1) Are we using the correct value for c6? I think pulser sometimes uses `c6 = 865723.02` instead of `c6 = 5420158.53`.
2) Are the occupation operators correct? Should they be `(1-Z)/2` instead of `(1+X)/2`?
3) Also there may be a factor of 2 discrepancy in the interaction hamiltonian. 
