From: Javier Vijande vijande@usal.es Date: Wed, 27 Jun 2007 10:17:33 +0200
I have another question, I would like to include a term in the hamiltonian to be solved in a 2D 4x4 square lattice of the form
H_s= -alpha * (x_i y_j - x_j y_i)
where the x and y reflect the position of the nearest neighbors, i=(x_i,y_i) and j=(x_j,y_j). I was thinking to use a term in the model definition like
<BONDTERM type="1" source="i" target="j"> -alpha*(x(i)*y(j)-x(j)*y(i))) </BONDTERM>
Is this correct or I need to define x and y and modify the lattice somewhere?.
No, currently site coordinate in BONDTERM is not supported. Although you can still use symbol 'x', 'y', etc, if you add
<INHOMOGENEOUS><EDGE/></INHOMOGENEOUS>
in your lattice definition (see, e.g., "inhomogeneous square lattice"), these symbols just return the coordinate of the bond center (not the coordinates of ends).
Best, Synge