CASTEP uses pseudopotentials to represent the interaction between core and valence electrons.
CASTEP supports both norm-conserving and Ultrasoft pseudopotentials. Pseudopotentials can be read from file in various formats. CASTEP also has its own built in generator and can compute potentials 'on-the-fly' during a calculation. There is a built in database of well tested potentials. In particular it is possible to generate highly accurate semi-core pseudopotentials which have been used in high pressure studies.
For more information on pseudopotentials in CASTEP see the following talks from the 2006 Castep workshop:
- Pseudopotentials Prof. Chris Pickard (UCL)