Dipole

Name TDEasyAxis
Section Time-Dependent::Response::Dipole
Type block

For magnon kicks only. This variable defines the direction of the easy axis of the crystal. The magnetization is kicked in the plane transverse to this vector

Name TDPolarization
Section Time-Dependent::Response::Dipole
Type block

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:

%TDPolarization
  pol1x | pol1y | pol1z
  pol2x | pol2y | pol2z
  pol3x | pol3y | pol3z
%

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.

Name TDPolarizationDirection
Section Time-Dependent::Response::Dipole
Type integer

When a delta potential is included in a time-dependent run, this variable defines in which direction the field will be applied by selecting one of the lines of TDPolarization. In a typical run (without using symmetry), the TDPolarization block would contain the three Cartesian unit vectors (the default value), and one would make 3 runs varying TDPolarization from 1 to 3. If one is using symmetry, TDPolarization should run only from 1 to TDPolarizationEquivAxes.

Name TDPolarizationEquivAxes
Section Time-Dependent::Response::Dipole
Type integer
Default 0

Defines how many of the TDPolarization axes are equivalent. This information is stored in a file and then used by oct-propagation_spectrum to rebuild the full polarizability tensor from just the first TDPolarizationEquivAxes directions. This variable is also used by CalculationMode = vdw.

Name TDPolarizationWprime
Section Time-Dependent::Response::Dipole
Type block

This block is needed only when TDPolarizationEquivAxes is set to 3. In such a case, the three directions (pol1, pol2, and pol3) defined in the TDPolarization block should be related by symmetry operations. If A is the symmetry operation that takes you from pol1 to pol2, then TDPolarizationWprime should be set to the direction defined by A$^{-1}$pol3. For more information see MJT Oliveira et al., J. Nanoscience and Nanotechnology 8, 3392 (2008).