The (real) polarization of the delta electric field. Normally
one needs three perpendicular polarization directions to calculate a
spectrum (unless symmetry is used).
The format of the block is:
Octopus uses both this block and the variable
TDPolarizationDirection to determine the polarization
vector for the run. For example, if
TDPolarizationDirection=2 the polarization (pol2x,
pol2y, pol2z) would be used.
These directions may not be in periodic directions.
The default value for TDPolarization is the three
Cartesian unit vectors (1,0,0), (0,1,0), and (0,0,1).
Note that the directions do not necessarily need to be perpendicular
when symmetries are used.
WARNING: If you want to obtain the cross-section tensor, the
TDPolarization block must be exactly the same for the run in
each direction. The direction must be selected by the
TDPolarizationDirection variable.