... (q, ivn) - 2 X:0(q, ivn) 2 1 – UX-0(q, ivn) + U*.xG(q. iv)] x G(k', ico ... icon - ido, and N denotes size of a square lattice. The term U*.xG,F on the ... (q, ivn) = TBN kido x [G(k+ q, icon + ivn)G(k, iaon) - F(k+ q, icon + iv.)F(-k, icon)] ...