CASTEP Core Level Spectroscopy Options dialog
The CASTEP Core Level Spectroscopy Options dialog allows you to specify the density of the k-point set and the eigenvalue convergence criterion used for core level spectra calculations.
The Monkhorst-Pack k-point grid to be used in the calculation can be specified in one of four ways:
Gamma point only: When selected, indicates that the density of states calculation uses a single k-point at (0,0,0).
Quality: When selected, generates the k-point grid using a k-point separation appropriate to the specified quality level. Select the desired quality level from the list. Available options are:
- Coarse
- Medium
- Fine
The k-point separations associated with the three Quality settings are as follows:
Quality | k-point separation (Å-1) |
---|---|
Coarse | 0.07 |
Medium | 0.05 |
Fine | 0.04 |
Separation: When selected, generates the k-point grid according to the specified k-point separation. Specify the k-point separation, in Å-1, in the associated text box.
When you select the Separation, the Monkhorst-Pack parameters are derived to give the specified separation between neighboring grid points.
Custom grid parameters: When selected, generates the k-point grid using the Monkhorst-Pack grid parameters and the origin shift in fractional reciprocal space coordinates specified in the Grid parameters and Origin shift text boxes, respectively.
Grid parameters: Specify the Monkhorst-Pack grid parameters in each of the lattice directions.
Actual spacing: Displays the k-point separation, in Å-1, resulting from the currently specified Monkhorst-Pack grid parameters in each of the lattice directions.
Origin shift: Specify the offset of the Monkhorst-Pack grid in fractional reciprocal space coordinates.
The Grid parameters and Origin shift controls are enabled only if you select the Custom grid parameters option.
Display points...: Displays the number and fractional coordinates of the reciprocal space mesh points that would be generated using the currently specified parameters.
The actual set of k-points that will be used in the calculations may be altered if the symmetry of the system changes.
Band energy tolerance: Specify the convergence criterion in eV for electronic eigenvalues during the core level spectroscopy calculation. The calculation will stop when all electronic eigenvalues change by less than this value over a single iteration of the electronic structure.
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