Use I for the square root of -1, and set the parameter COMPLEX to true in the exact diagonalization input file On 12 Mar 2011, at 16:33, javad vahedi wrote:

Dear Prof.Matthias

Let's taking DM interaction in z-direction, so we have (SxSy-SySx) , which gives an imaginary part 1/4i{(S+S+)-(S+S-)-(S-S+)+(S-S-)}.

I have no idea how to deal with it.

------- Best Regards Javad Vahedi,