><h2 id="1">Spin wave spectrum of La2CuO4</h2><p>Crystal structure of La2CuO4 contains Cu2+ atoms with S = 1/2 spin on a square lattice. Exchange parameters are taken from the paper: R. Coldea, Phys. Rev. Lett. <b>86</b>, 5377 (2001). The exchanges are corrected for the ring exchange but the energy renormalization factor included in the paper is not applied.</p><pre class="codeinput">J   = 138.3;
Jp  = 2;
Jpp = 2;
Jc  = 38;

lacuo = sw_model(<span class="string">'squareAF'</span>,[J-Jc/2 Jp-Jc/4 Jpp]/2,0);
