cvmclus

This code generates all the input coefficients needed to construct the CVM (Cluster Variation Method) entropy expression.

S= - k_Boltzmann sum_c k_c sum_j m_{j,c} rho_{j,c} ln(rho_{j,c})

where
   rho_{.,c} = V_c xi (this is a matrix * vector multiplication)
   
and where
  c: symmetrically distinct clusters (a cluster is just a set of sites)
  j: symmetrically distinct configurations on c
  k_c: Kikuchi-Barker coefficients for cluster c
  m_{j,c}: multiplicity for configuration j on cluster c.
  rho_{j,c}: probability for configuration j on cluster c.
  rho_{.,c}: vector of rho_{j,c} for a fixed c.
  V_c: v-matrix for cluster c
  xi: vector of all correlations for all clusters considered
       (including possible functions on each sites for systems beyond binary).

It takes as an input
(1) a lattice (by default in lat.in) in a format identical to (m)maps.
    (See corrdump -h for a description.)
(2) a maximal cluster (by default in maxclus.in) defined by a list of sites,
    expressed in the coordinate system defined by the first lines of lat.in.
    Multiple maximal clusters can be specified, separated by a line containing
    only the word 'end'.

It produces as an output:
(1) clusters.out, the list of all symmetrically distinct subclusters of the maximal cluster,
     in the standard ATAT format (See corrdump -h for a description.)
     These include not only the set of sites but also, for systems beyond binaries, possible functions
     on each sites of the subclusters, so one set of sites may appear more than once.

(2) clusmult.out, the multiplicities (per unit cell) for each clusters given in (i).
    The file starts with the number of clusters and then lists their multiplicities.
    (That information in in (i) too, but they are separated out here for convenience.
    This is not needed for the CVM entropy, only for the energy expression:
        E = sum_q J_q mu_q xi_q
      where q is a cluster with functions (for beyond binary)
            J_q are the Effective Cluster Interations (not provided by this code)
	    xi_q is the correlation associated with q (one element of xi_q)
	    mu_q are in clusmult.out
    
(3) config.out, the list of all configurations on each of the clusters.
    (Note that there may be fewer clusters than in clusters.out because, here, we only consider
    sets of sites without possible different functions acting on them.)
    Format:
     [nb of clusters n]
     repeated for each of the n clusters:
      [nb of config c for current cluster]
      repeat for each of the c config:
       [number of sites in the cluster]
       repeat for each site:
        [coordinates of the site] [occupation: as a integer in {0,...,k-1}] [k]
     (indentation is for clarity - the actual file is not indented.)	

(4)  vmat.out, the `v-matrix'. There is one v-matrix per cluster and
     each v-matrix has different correlations along columns and different configurations along rows
     the order is the same as in clusters.out and config.out. Format:
     [nb of clusters n]
     repeated for each of the n clusters:
      [number of rows (config)] [number of columns (clusters)]
      [vmatrix, each column separated by space and each row separated by newlines]

(5)  configmult.out, the multiplicities of the configurations on each cluster. Format:
     [number of clusters n]
     repeat for each of the n clusters:
      [number of config c on current cluster]
      for each of the c config:
       [the multiplicity of the current config]
     Note: the same order as in config.out is used.

(6)  configkb.out, the Kikuchi-Barker coefficients of each cluster. Format:
     [number of clusters n]
     repeat for each of the n clusters:
       [Kikuchi-Barker coefficient]
     Note: the same order as in config.out is used.