CASTEP > Dialogs in CASTEP > CASTEP Calculation dialog > Electronic tab > CASTEP Electronic Options dialog > Potentials tab - CASTEP Electronic Options dialog

Potentials tab

The Potentials tab allows you to control which pseudopotentials will be used for each element in the structure.

Scheme: Select the type of pseudopotential to be used. This will override the Pseudopotentials option specified on the Electronic tab. Three different types of pseudopotential are available:

The latest set of OTFG settings introduced in Materials Studio 8.0 has been developed in order to minimize the error with respect to fully converged all-electron DFT calculations. The error achieved by this set is 0.5 meV/atom which puts CASTEP among the most accurate pseudopotential codes available. A full definition of the test framework and the meaning of the error is given by Lejaeghere et al. (2014) and on the website of the Delta project. The files that correspond to this set have an _80 suffix.

It is not recommended to use PW91 exchange-correlation functional when requesting on the fly generation of pseudopotentials; PBE, RPBE, or PBESOL are better options when a GGA functional is required.

When you specify the type of pseudopotential to be used in this way, the default pseudopotential of that type for each element will be used in the calculation.

Representation: Choose between Reciprocal space and Real space representations of the pseudopotentials. This will override the Pseudopotential representation option specified on the Electronic tab.

The real space representation may give a performance advantage for large systems.

More...: Provides access to the CASTEP Real Space Potentials dialog, which allows you to specify details of the transformation of pseudopotentials to a real space representation.

This button is enabled only if Real space is selected from the Representation dropdown list.

Selected potentials: Displays information about the selected pseudopotentials for each element in a grid.

There is a row in the grid for each element. The element type, current pseudopotential, energy, and valence are displayed. To select a different pseudopotential for a particular element, click in the appropriate pseudopotential grid cell and choose a new pseudopotential from the dropdown list.

If changes are made to the default pseudopotentials, the Scheme displayed is Custom.

Show potentials for all elements: When checked, the Selected potentials list will display information about all elements in the periodic table for which pseudopotentials are available. Otherwise, only elements present in the current structure are displayed in the list. Default = unchecked.

View: Displays a modal view on the selected pseudopotential file.

External Potential

Electric field: Specify the external electric field strength, in eV/Å/e.

Field direction (X Y Z): Vector specifying the direction of the electric field.

Only systems that contain molecules or slabs are appropriate for electric field calculations.
For slabs, the field must be along the surface normal. In both cases atoms should be positioned in the middle of the cell.

The field direction is specified in Cartesian coordinates. The values of the X, Y, and Z direction components of the electric field are interrelated. The three field components are used to define a unit vector. When a job is launched the direction components are normalized to give a unit vector which is then multiplied by the field magnitude to give the actual field components. Entering a vector with all zero components has the same effect as entering a (111) vector.

Access methods

Menu Modules | CASTEP | Calculation | Electronic | More... | Potentials
Toolbar CASTEP | Calculation | Electronic | More... | Potentials
See Also:

Pseudopotentials
Setting electronic options
Setting system parameters
Electronic tab - CASTEP Calculation dialog
Basis tab - CASTEP Electronic Options dialog
SCF tab - CASTEP Electronic Options dialog
k-points tab - CASTEP Electronic Options dialog
CASTEP Real Space Potentials dialog

Accelrys Materials Studio 8.0 Help: Wednesday, December 17, 2014
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