AVERAGE_BEAMS

AVERAGE_BEAMS can be used to turn averaging of symmetry-equivalent beams off, or to make it follow a different averaging scheme than would be dictated by BEAM_INCIDENCE. This can be useful to e.g. enforce “normal-incidence averaging” for slightly off-normal incidence, or to force calculation of multiple equivalent theoretical beams at normal incidence. However, use of this parameter is not recommended for the general case.

Default: Use averaging as given by BEAM_INCIDENCE

Syntax:

AVERAGE_BEAMS = off     ! ignore symmetry equivalence entirely. Alias: 'none', 'false'
AVERAGE_BEAMS = all     ! pretend that beam incidence is perpendicular (equivalent to setting '0 0'). Alias: 'perpendicular'
AVERAGE_BEAMS = 0 0     ! same as above
AVERAGE_BEAMS = THETA 0.3, PHI 10.1
AVERAGE_BEAMS = 0.3 10.1

Acceptable values: off, none, false / all, perpendicular / beam incidence specified by theta and phi, following the same syntax as specified in BEAM_INCIDENCE

See page on BEAM_INCIDENCE for details on the definition of theta and phi.

If AVERAGE_BEAMS is disabled entirely (i.e. off), then IVBEAMS and EXPBEAMS.csv are taken at face value. Only beams with the same label will be recognized as equivalent and compared in the \(R\)-factor calculation. If IVBEAMS is not present, the generated IVBEAMS file will contain the same beams as the EXPBEAMS.csv file. Note that this affects not only spot equivalences due to mirror or rotation symmetry, but also disables equivalence based on multiple rotational domains that may be present on the surface. Averaging over rotational domains, but not over mirror/rotation symmetries can be achieved by defining an arbitrary, non-zero theta, and a phi that is not parallel to any mirror plane.