Hi I simple want to write a script for 2d square lattice, with AFM Heisenberg interaction on nearest and next nearest neighbor bonds. How do I know if naming them respectively J0, and J1 (both AFM) should work or not? If I name them instead J1 and J2 should that work? My input file presently looks like: parms.append( { 'LATTICE' : "frustrated square lattice", 'T' : t, 'J0' : -1 , 'J1' : -0.5 , 'THERMALIZATION' : 10000, 'SWEEPS' : 500000, 'UPDATE' : "cluster", 'MODEL' : "Heisenberg", 'L' : 8, 'W' : 8 } ) I want NN J to be 1.0 and NNN J to be 0.5. Is that going in properly? The term "frustrated" in front of "square lattice", should that be necessary? What would be the extension of the name for the lattice when I do a cubic lattice, say, with J1 (NN), J2 (NNN), J3(NNNN)? How do I know in that case which direction is preferentially x, y and z? Thanks in advance for all the replies. Swagata -- *........................................................................................................................................................................Swagata Acharya* Dept. of Physics and Meteorology IIT Kharagpur B C Roy Hall of Residence Room NW 204 Mob: +91 9836893829 +91 9088377636 Volunteer : Padakshep , Vivekananda Study Circle Secretary: Padakshep(www.padakshep.org) *................................................................................................................................*