ALPS community,

I am interested in calculating the states and the spin-spin correlation functions for a dimerized chain.  This type of structure is sometimes called an alternating chain.  It consists of spins coupled along one-dimension with alternating strong and weak Heisenberg exchange parameters:

J0---J1---J0---J1---J0---

Using the tutorials and the ALPS website, I have assembled what I think are the correct UNITCELL and LATTICEGRAPH (see end of message).

Q1:  Is there a way to check this definition visually?  The wiki suggests the command

printgraph parameter_file

Q2:  does the predefined ‘MODEL’ “spin” account for J0 and J1 exchange?

Q3: Can ‘S’ also be a conserved quantum number.

Thanks for your assistance.

Matt Stone

parms = [{

          'LATTICE'                   : "dimechain",

          'LATTICE_LIBRARY'           : "latticeCN.xml",

          'MODEL'                     : "spin",

          'local_S'                   : 0.5,

          'J0'                        : 1,

          'J1'                        : 0.125,

          'L'                         : 6,

          'CONSERVED_QUANTUMNUMBERS'  : 'Sz',

          'MEASURE_CORRELATIONS[Diagonal spin correlations]='   : 'Sz',

          'MEASURE_CORRELATIONS[Offdiagonal_spin_correlations1]' : 'Splus:Sminus',

          'MEASURE_CORRELATIONS[Offdiagonal_spin_correlations2]' : ‘Sminus:Splus,

          'D'                         : 0.0,

          'h'                         : 0.0,

          }]

<UNITCELL name="anisotropic1d" dimension="1">

  <VERTEX/>

  <EDGE type="0">

    <SOURCE vertex="1" offset="0"/>

    <TARGET vertex="1" offset="0.5"/>

  </EDGE>

  <EDGE type="1">

    <SOURCE vertex="1" offset="0.5"/>

    <TARGET vertex="1" offset="1"/>

  </EDGE>

</UNITCELL>

<LATTICEGRAPH name = "dimechain" vt_name="dimechainLattice">

  <FINITELATTICE>

   <LATTICE ref="chain lattice"/>

    <EXTENT dimension="1" size="L"/>

    <BOUNDARY dimension="1" type="periodic"/>

  </FINITELATTICE>

  <UNITCELL ref="anisotropic1d"/>

</LATTICEGRAPH>

<!-- From the default lattices -->

<LATTICE name="chain lattice" dimension="1">

  <PARAMETER name="a" default="1"/>

  <BASIS><VECTOR>a</VECTOR></BASIS>

  <RECIPROCALBASIS><VECTOR>2*pi/a</VECTOR></RECIPROCALBASIS>

</LATTICE>