Dear Oleh,
It seems that your lattice “p_lat” is not defined in THREE dimensions, but in TWO dimensions. Are you really simulating three-dimensional model?
Best, Synge
On 2014/09/29, at 5:09, Menchyshyn Oleh oleh.menchyshyn@gmail.com wrote:
Dear ALPS community,
I am trying to obtain the critical temperature for the 3D ferromagnetic Heisenberg model S=1/2 on the cubic lattice with a unit cell which contains 16 atoms. I have made the QMC "loop" simulations for the lattice with dimensions L = 8, i.e. 8*8*8 unit cells, also for L=10, and L=12. But there was just a little bend on the magnetisation curve as a sign of the phase transition which should occur for the ferromagnetic model for certain. I know I should use the Binder cumulant and the finite size scaling to locate the phase transition point correctly. I have enlarged my lattice to L=24, but simulation goes very-very slowly. As I have limited resources to just tens of cores and I have a feeling I would need to take L=32(48?) at least I want to ask:
Based on your experience what order should be the THERMALIZATION and SWEEPS parameters? How can I estimate the computational complexity of my problem and the time it would take? Or maybe, I do anything wrong?
A one more technical issue. The tutorial on the ALPS says that correctness of a lattice definition can be checked with "printgraph" tool. I used it with a couple definition files but all resulted in:
Caught exception: parameter parse error at "<LATTICES> <LATTICEGRAPH name="p"
Just for a reference I put a definition of a lattice I know worked well with simulation tools, but failed with "printgraph"
<LATTICES> <LATTICEGRAPH name="p_lat"> <FINITELATTICE> <LATTICE dimension="2"> <BASIS> <VECTOR>1 0</VECTOR><VECTOR>0 1</VECTOR></BASIS> </LATTICE> <PARAMETER name="L"/> <PARAMETER name="M"/> <EXTENT dimension="1" size="L"/> <EXTENT dimension="2" size="M"/> <BOUNDARY type="periodic"/> </FINITELATTICE> <UNITCELL dimension="2" vertices="6"> <VERTEX id="1"><COORDINATE> 0.6 0.2 </COORDINATE></VERTEX> <VERTEX id="2"><COORDINATE> 0.6 0.6 </COORDINATE></VERTEX> <VERTEX id="3"><COORDINATE> 0.2 0.6 </COORDINATE></VERTEX> <VERTEX id="4"><COORDINATE> 0.2 0.2 </COORDINATE></VERTEX> <VERTEX id="5"><COORDINATE> 0.8 0.4 </COORDINATE></VERTEX> <VERTEX id="6"><COORDINATE> 0.4 0.8 </COORDINATE></VERTEX> <EDGE type="2"><SOURCE vertex="1"/><TARGET vertex="2"/></EDGE> <EDGE type="2"><SOURCE vertex="2"/><TARGET vertex="3"/></EDGE> <EDGE type="2"><SOURCE vertex="3"/><TARGET vertex="4"/></EDGE> <EDGE type="2"><SOURCE vertex="1"/><TARGET vertex="4"/></EDGE> <EDGE type="3"><SOURCE vertex="1"/><TARGET vertex="5"/></EDGE> <EDGE type="3"><SOURCE vertex="2"/><TARGET vertex="6"/></EDGE> <EDGE type="1"><SOURCE vertex="2"/><TARGET vertex="5"/></EDGE> <EDGE type="1"><SOURCE vertex="3"/><TARGET vertex="6"/></EDGE> <EDGE type="3"><SOURCE vertex="3"/><TARGET vertex="5" offset="-1 0"/></EDGE> <EDGE type="1"><SOURCE vertex="4"/><TARGET vertex="5" offset="-1 0"/></EDGE> <EDGE type="3"><SOURCE vertex="4"/><TARGET vertex="6" offset="0 -1"/></EDGE> <EDGE type="1"><SOURCE vertex="1"/><TARGET vertex="6" offset="0 -1"/></EDGE> </UNITCELL> </LATTICEGRAPH> </LATTICES>
Best regards, Oleh Menchyshyn