The Band Structure Options dialog allows you to specify a custom reciprocal space path and the eigenvalue convergence criterion used for band structure calculations.
Use separate XC functional for band structure calculation: When checked, allows you to select a different exchange-correlation functional for the band structure calculation from the one used in the self-consistent calculation.
This feature is particularly useful for carrying out expensive, screened exchange calculations. Perform the main run with the LDA or GGA functional, then invoke screened or exact exchange in non self-consistent mode during the band structure calculation.
There is an important difference between standard DFT calculations with local exchange-correlation potentials and the nonlocal exchange case. The potential used in the latter scenario depends on the SCF k-points, while in the former case, the potential depends only on electron density. This difference can make all properties calculations a lot more expensive in terms of memory usage and CPU time, so it is advisable to limit the number of SCF k-points that you use in such situations. This is particularly relevant for small unit cells, where the default settings may generate a very large k-point set.
Functional: Select the type of exchange-correlation potential to be used in the band structure calculation.
Choose the type of functional from the first dropdown list. Available options are:
Then, if appropriate, select the specific functional from the second dropdown list. Depending on the functional type selected from the first dropdown list, some of the following options may be available:
This option is enabled only when Use separate XC functional for band structure calculation is checked.
Band energy tolerance: Specify the convergence criterion for electronic eigenvalues during the band structure calculation. The calculation will stop when all electronic eigenvalues change by less than this value over a single iteration of the electronic structure.
More information about the symmetry labels used in the Band Structure Options dialog can be found in Bradley and Cracknell (1972).
Path...: Provides access to the Brillouin Zone Path dialog, which allows you to specify a custom reciprocal space path.
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Properties tab - CASTEP Calculation dialog