Dear Prof. Troyer,
Thank you for the reply.
I take this reference result from the paper by Jill C. Bonner and Michael E. Fisher: "The Entropy of an Antiferromagnet in a Magnetic Field", Proc. Phys. Soc. 80, 508 (1962) doi:10.1088/0370-1328/80/2/318
I do get the low temperature convergence towards the correct result from the exact diagonalization program in ALPS (with smaller lattice size L=8) but because I intend to test on other bigger 2D lattices (for which the ALPS ED crashes with std::bad_alloc()), I guessed that QWL might be a good option.
Regards, Vipin
On Fri, 26 Jul 2013, Matthias Troyer wrote:
Dear Vipin,
where do you get the value 0.4812 from?
On Jul 26, 2013, at 4:47, Vipin Varma varma@th.physik.uni-bonn.de wrote:
Dear all,
I am trying to use the Quantum-Wang-Landau (QWL) algorithm to calculate the entropy of a linear chain spin-1/2 model with Jxy=0 in a field h=1, which is classical but QWL seems to be suggested for entropy calculations.
However with forty sites and down to low temperatures, I don't seem to be getting near the correct entropy density result of S ~ 0.4812 ...
The parameter file is <<<<<<<<<<<<<<<<<<<<<<<<<< LATTICE="chain lattice" MODEL="spin" local_S=1/2 h=1 J = 1 Jxy = 0 CUTOFF = 500 {L=40} <<<<<<<<<<<<<<<<<<<<<<<<<
and a partial output of entropy density versus temperature is
<SNIP> </PARAMETERS> <legend show="true"/> <xaxis label="Temperature"/> <yaxis label="Entropy Density"/> <set label=""> <point><x>0.10000000000000001</x><y>0.065628773413218822</y></point> <point><x>0.20000000000000001</x><y>0.13394955300729872</y></point> <point><x>0.30000000000000004</x><y>0.24229259030929573</y></point> <point><x>0.40000000000000002</x><y>0.31481859757794478</y></point> <point><x>0.5</x><y>0.39826073000393336</y></point> <point><x>0.59999999999999998</x><y>0.46128739087861204</y></point> <point><x>0.69999999999999996</x><y>0.50938492873462538</y></point> <point><x>0.79999999999999993</x><y>0.5481023575910553</y></point> <point><x>0.89999999999999991</x><y>0.57776445729654646</y></point> <point><x>0.99999999999999989</x><y>0.59988758184662683</y></point> <point><x>1.0999999999999999</x><y>0.61635447545226674</y></point> <SNIP>
I have tried changing the lattice length and cut-off but not much changes.
Any advice on what I might be doing wrong will be greatly appreciated.
With regards, Vipin