CASTEP

Author

M. Segall, M. Probert, C. Pickard, P. Hasnip, S. Clark, K. Refson and M. Payne.

Contributors:
P. Lindan, P. Haynes, J. White, V. Milman, N. Govind, M. Gibson, P. Tulip, V. Cocula, B. Montanari and D. Quigley.

Origin

Distributed under the terms of an Agreement between the United Kingdom Car-Parrinello (UKCP) Consortium, Daresbury Laboratory and Accelrys, Inc.

Version

CASTEP 4.2 & 4.0.1

Official Web Site

http://www.tcm.phy.cam.ac.uk/castep/index.html

Brief Program Description

CASTEP is a density functional code that uses a plane-wave basis set and pseudopotentials to simulate the properties of solids, interfaces and surfaces for a wide range of materials.

Specific features of the program include:

• Calculation of total energies of crystal structures

• Geometry optimisations including simultaneous optimization of cell and internal co-ordinates

• Molecular dynamics

• Calculation of harmonic phonon frequencies and eigenvectors using density functional perturbation theory

There is some new functionality in this version of the code compared to the previous version (3.1) including:

• Fourier interpolation of dynamical matrices over the BZ for much faster DFPT lattice dynamics calculations of phonon dispersion and DOS

• Finite displacement and supercell method for lattice dynamics of metallic systems and ultrasoft pseudopotentials

• Wannier Functions

• Infra-red intensities calculated for LR phonon at gamma point

• Frequency-dependent dielectric permittivity (in IR range)

• Spin-dependent initial density for density-mixing method

• Path-integral molecular dynamics

Areas of Application

CASTEP can be used to simulate the properties of solids, interfaces, and surfaces for a wide range of materials classes including ceramics, semiconductors, and metals. First principle calculations allow researchers to investigate the nature and origin of the electronic, optical, and structural properties of a system with high accuracy without the need for any experimental input other than the atomic number of mass of the constituent atoms.

CASTEP offers simulation capabilities not found elsewhere, such as accurate prediction of phonon spectra, dielectric constants, and optical properties. It is well suited to research problems in solid state physics, materials science, chemistry, and chemical engineering where researchers can employ computer simulations to perform virtual experiments which can lead to tremendous savings in costly experiments and shorter developmental cycles.

The release notes for version 4.0.1 of the code can be found in the $CHEM/doc/castep4 directory, and version 4.2 in the $CHEM/doc/castep42 directory.

Implementation and Access

The command runcastep accesses and executes the computational chemistry program CASTEP 4.0.1. CASTEP runs both in serial and in parallel on Magellan.

Due to license restrictions, users must have signed a CASTEP license agreement before they can be given access to the code. If you would like to use the code, then please contact Helen Tsui at helen.tsui@imperial.ac.uk.

CASTEP requires two input files plus one or two additional pseudopotential files for every element included. The filenames of both input and output files begin with a common root, known as a seed where seed is the name that is passed to the runscript. This makes it easy to distinguish the files belonging to a particular run. The two input files are seed.cell which describes the simulation cell and its contents, and seed.param which describes the type of run to be performed and any options which may be required. If this is omitted a single-point energy calculation with default parameters is performed.

Access is via the command:

$CHEM/runcastep seed

There are also a number of tools available with CASTEP. The Fortran tools are mostly used for extracting information from an output file and converting it to a form that is readable by a graphics package. These tools are located in the directory $CHEM/Castep-4.01/Utilities/cteprouts on Magellan and can be accessed by writing the relevant command to a script and submitting it to the a1 queue as described above. More information about the functions of each tool can be found in the User Guide.

The are also a number of PERL tools which are located in the $CHEM/Castep-4.01/Utilities/cteprouts directory on Magellan.

These are mostly used to convert various file types into a format that is readable by this version of CASTEP. Again, these can be accessed by writing the relevant command to a script and submitting it to the queue as described above. More information can be found in the README file in the $CHEM/doc/castep4 directory.

CASTEP version 4.2 is available on Magellan and runs both in serial and parallel. This can be accessed using the $CHEM/runcastep42 command. There are also a number of utilities available with CASTEP. The Fortran tools are mostly used for extracting information from an output file and converting it to a form that is readable by a graphics package. These are located in the directory $CHEM/Castep-4.2/Utilities.

The previous version of the code (CASTEP 3.1.1) is still available via the $CHEM/runcastep3 runscript. Please see the runcastep3 man page for more information.

Machines

Version 4.2 & 4.0.1 are available on Magellan.

Documentation

The CASTEP User Guide is available as a PDF file from the $CHEM/doc/castep4 directory.

There is a Unix-style man page containing information on the local implementation of CASTEP version 4.0.1, accessible by typing: man runcastep. The corresponding man page for version 4.2 is accessible by typing: man runcastep42.

Further information can also be found on the CASTEP website:
http://www.tcm.phy.cam.ac.uk/castep/

Literature References

M. D. Segall, P. L. D. Lindan, M. J. Probert, C. J. Pickard, P. J. Hasnip, S. J. Clark, M. C. Payne J. Phys.: Cond. Matt. 14(11) pp.2717-2743 (2002).

Specialist Support

Dr Helen Tsui. Address: Department of Chemistry, Imperial College London, South Kensington, London SW7 2AZ. Tel: 020 7594 1220 Email: helen.tsui@imperial.ac.uk.

Program Restrictions and Comments

Users are required to include the following citation for CASTEP in any reports or published results obtained with the software:

"First-principles simulation: ideas, illustrations and the CASTEP code", J. Phys.: Cond. Matt. 14(11) pp.2717-2743 (2002), M. D. Segall, P. J. D. Lindan, M. J. Probert, C. J. Pickard, P. J. Hasnip, S. J. Clark and M. C. Payne.