# 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 Yes 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 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 0.0001 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.