minimize rigid {<minimize-rigid-statement>} end

<minimize-rigid-statement> :==

  ?
  --{Print current information.}
  nstep=<integer>
  --{Number of minimization steps to perform. Default=500}
  drop=<real>
  --{Expected initial drop in total energy. Default=0.001}
  tolerance=<real>
  --{Tolerence for early termination of minimization. If the norm
     of the gradient of the total energy falls below this value
     minimization will stop. Default=0.0001}
  nprint=<integer>
  --{Frequency of printing energy values. Default=1}
  group=<atom-selection>
  --{Selects atoms that will form a rigid group during minimization,
    multiple specification define multiple rigid groups. The group
    selections must be disjoint. The default group consists of all
    free atoms. This default is overwritten as soon as a group statement
    is issued.}
  translation=<logical>
  --{If false the last group is not translated. If true all groups
     are translated. Default=true}

  --{Only atoms selected in groups are moved. The target function is the
     total energy. Therefore, desired energy terms (such as packing energy,
     structure factor difference) should be selectively turned on or 
     off before invoking this procedure.}