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Overview

CASTEP has a built-in library of pseudopotentials which is usually updated each release. We refer to CASTEP's build-in pseudopotentials as on-the-fly generated (or OTFG). The default OTFG pseudopotentials are accurate ultrasoft pseudopotentials. These are used if species_pot block is not defined in the cell file - or an empty block is given 

%block species_pot
%endblock species_pot

For preliminary investigations and high-throughput calculations you might want to choose the QC5 set of ultrasoftpotentials which are faster, but slightly less accurate than the default set. These are designed to give converged results at 500eV for all elements: 

%block species_pot
QC5
%endblock species_pot

For properties that require norm-conserving pseudopotentials, you can select CASTEP's latest OTFG norm-conserving set with the following in the in your .cell file. 

%block species_pot
NCP
%endblock species_pot
For backwards compatibility you can also select pseudopotentials from earlier versions on the on-the-fly database, e.g. use 
%block species_pot
C17
%endblock species_pot
to select the ultrasoft pseudopotentials from CASTEP version 17. You can also specify the pseudopotential on a per-element basis, e.g. 
%block species_pot
Fe  C17
 O  NCP
Ba  QC5
%endblock species_pot

A complete list of the availible OTFG definitions follows:

String Description
NCP Alias for the most recent set of norm conserving potentials
QC5 High through put set (delta=1.7meV, 0.8meV excluding N,O,Cr,Mn)
HARD "Ultimate" set of HARD pseudopotentials
C7 USP definitions as of CASTEP 7.0 (C7)
C8 USP definitions as of CASTEP 8.0 (C8)
C9 USP definitions as of CASTEP 9.0/16.0 delta=0.5meV
NCP9 Set of Norm Conserving pseudopotentials CASTEP 9.0/16.0 (NCP9)(delta=1.1meV)
C17 USP definitions, CASTEP 17.0 (C17)
NCP17 Set of Norm Conserving pseudopotentials CASTEP 17.0 (NCP17)
C18 USP definitions, CASTEP 18.0 (C18)
NCP18 Norm Conserving pseudopotentials CASTEP 18.0 (NCP18)
C19 USP definitions, CASTEP 19.0 (C19) delta=0.442 meV (default for CASTEPv19 up to and including CASTEPv24) 1
NCP19 Norm Conserving pseudopotentials CASTEP 19.0 (NCP19) delta=1.098 meV
C19mk2 USP definitions. Updated Lanthanide and Actinide definitions, but otherwise identical to C19. Default for CASTEPv25 and later 2

Pseudopotential files

CASTEP can also read in pseudopotentials from files

Format Origin
.usp as generated by CASTEP (note both USP and NCP use this format)
.uspso as generated by CASTEP, with spin-orbit coupling
.recpot as generated by OPIUM (also legacy CASTEP files)
.UPF as generated by Quantum Espresso

Note that properties using PAW augmentation will not be available when using file based pseudopotentials (OTFG is required) - this includes all NMR/EPR properties and EELS spectra.

  1. Kurt Lejaeghere, Gustav Bihlmayer, Torbjörn Björkman, Peter Blaha, Stefan Blügel, Volker Blum, Damien Caliste, Ivano E. Castelli, Stewart J. Clark, Andrea Dal Corso, Stefano de Gironcoli, Thierry Deutsch, John Kay Dewhurst, Igor Di Marco, Claudia Draxl, Marcin Dułak, Olle Eriksson, José A. Flores-Livas, Kevin F. Garrity, Luigi Genovese, Paolo Giannozzi, Matteo Giantomassi, Stefan Goedecker, Xavier Gonze, Oscar Grånäs, E. K. U. Gross, Andris Gulans, François Gygi, D. R. Hamann, Phil J. Hasnip, N. A. W. Holzwarth, Diana Iuşan, Dominik B. Jochym, François Jollet, Daniel Jones, Georg Kresse, Klaus Koepernik, Emine Küçükbenli, Yaroslav O. Kvashnin, Inka L. M. Locht, Sven Lubeck, Martijn Marsman, Nicola Marzari, Ulrike Nitzsche, Lars Nordström, Taisuke Ozaki, Lorenzo Paulatto, Chris J. Pickard, Ward Poelmans, Matt I. J. Probert, Keith Refson, Manuel Richter, Gian-Marco Rignanese, Santanu Saha, Matthias Scheffler, Martin Schlipf, Karlheinz Schwarz, Sangeeta Sharma, Francesca Tavazza, Patrik Thunström, Alexandre Tkatchenko, Marc Torrent, David Vanderbilt, Michiel J. van Setten, Veronique Van Speybroeck, John M. Wills, Jonathan R. Yates, Guo-Xu Zhang, and Stefaan Cottenier. Reproducibility in density functional theory calculations of solids. Science, 351(6280):aad3000, 2016. URL: https://www.science.org/doi/abs/10.1126/science.aad3000, arXiv:https://www.science.org/doi/pdf/10.1126/science.aad3000, doi:10.1126/science.aad3000. ↩

  2. Sebastiaan P. Huber, Emanuele Bosoni, Marnik Bercx, Jens Bröder, Augustin Degomme, Vladimir Dikan, Kristjan Eimre, Espen Flage-Larsen, Alberto Garcia, Luigi Genovese, Dominik Gresch, Conrad Johnston, Guido Petretto, Samuel Poncé, Gian-Marco Rignanese, Christopher J. Sewell, Berend Smit, Vasily Tseplyaev, Martin Uhrin, Daniel Wortmann, Aliaksandr V. Yakutovich, Austin Zadoks, Pezhman Zarabadi-Poor, Bonan Zhu, Nicola Marzari, and Giovanni Pizzi. Common workflows for computing material properties using different quantum engines. npj Computational Materials, 7(1):136, Aug 2021. URL: https://doi.org/10.1038/s41524-021-00594-6, doi:10.1038/s41524-021-00594-6. ↩