Symmetry
********

The symmetry of the system is automatically detected. Normally the
symmetry of the initial system is maintained. One can lower the
symmetry with the "Symmetry" key. In such cases the keyword
"POTENTIALNOISE" can force the solution away from the initial
symmetry.

Whether or not symmetry should be used can be controlled vial the
"UseSymmetry" key

   UseSymmetry Yes/No

"UseSymmetry"
   Type:
      Bool

   Default value:
      Yes

   Description:
      Whether or not to exploit symmetry during the calculation.

One can also select a sub set of symmetry operators:

   SubSymmetry integer_list

"SubSymmetry"
   Type:
      Integer List

   Description:
      The indices of the symmetry operators to maintain.

To get the indices of the symmetry operators, you should first run the
calculation with the following options added to your input:

    print symmetry
    stopafter gemtry

   and then you look in the output for (here the first four operators are listed)


   ::

       64    SYMMETRY OPERATORS:

    NO               MATRIX              TRANSL        AXIS    DET   ROTATION
    --------------------------------------------------------------------------

    1)        1.000   0.000   0.000       0.000       0.000    1.0       1
              0.000   1.000   0.000       0.000       0.000
              0.000   0.000   1.000       0.000       1.000

    2)        1.000   0.000   0.000       0.000       0.000    1.0       1
              0.000   1.000   0.000       5.400       0.000
              0.000   0.000   1.000       0.000       1.000

    3)        1.000   0.000   0.000       5.400       0.000    1.0       1
              0.000   1.000   0.000       0.000       0.000
              0.000   0.000   1.000       0.000       1.000

    4)        1.000   0.000   0.000       5.400       0.000    1.0       1
              0.000   1.000   0.000       5.400       0.000
              0.000   0.000   1.000       0.000       1.000

from this list you should select the desired operators and use that in
your final calculation, for example:

   SubSymmetry 1 7 21 31


Symmetry breaking for SCF
=========================

   PotentialNoise float

"PotentialNoise"
   Type:
      Float

   Default value:
      0.0001

   Description:
      The initial potential for the SCF procedure is constructed from
      a sum-of-atoms density. Added to this is some small noise in the
      numerical values of the potential in the points of the
      integration grid. The purpose of the noise is to help the
      program break the initial symmetry, if that would lower the
      energy, by effectively inducing small differences between
      (initially) degenerate orbitals.
