Hi, Alexander,
On Thu, Jul 21, 2011 at 4:06 PM, Alexander Herzog A.Herzog@fkf.mpg.de wrote:
I intend to perform a DMRG calculation for a dimerized antiferromagnetic chain, i.e.
H=J\sum(1+(-1)^j d)S_j S_j+1.
I'm not quite sure, if I use the proper definitions in my program. Thus I would like to reassure myself. Do you think, it will be appropriate to run the program with the following specifications?
LATTICE="open chain lattice" LATTICE_LIBRARY="C:\Programme\ALPS\lib\xml\lattices.xml" MODEL_LIBRARY="C:\Programme\ALPS\lib\xml\models.xml" MODEL="spin" CONSERVED_QUANTUMNUMBERS="N,Sz" Sz_total=0 J=1 J2=2 SWEEPS=6 NUMBER_EIGENVALUES=1 MEASURE_AVERAGE[Magnetization]=Sz MEASURE_AVERAGE[Exchange]=exchange MEASURE_LOCAL[Local magnetization]=Sz MEASURE_CORRELATIONS[Diagonal spin correlations]=Sz MEASURE_CORRELATIONS[Offdiagonal spin correlations]="Splus:Sminus" L=100 { MAXSTATES=30 }
J2 is the coupling for J_{2} S_{i} S_{i+2} (second nearest neighbor). I think your expression and the
Actually, parameters allow arithmetic calculation, therefore adding "inhomogeneous open chain lattice" in the lattices.xml file[1] and setting J in the parameter file as:
LATTICE="inhomogeneous open chain lattice" J=(1+(-1)^x)
will give you exactly what you want.
[1] "inhomogeneous open chain lattice" can be defined by following element: <LATTICEGRAPH name = "inhomogeneous open chain lattice"> <FINITELATTICE> <LATTICE ref="chain lattice"/> <EXTENT dimension="1" size ="L"/> <BOUNDARY type="open"/> </FINITELATTICE> <UNITCELL ref="simple1d"/> <INHOMOGENEOUS><VERTEX/></INHOMOGENEOUS> </LATTICEGRAPH>
Best regards,