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.