ASE Manual Release 3.6.1.2825 CAMd - CampOS Wiki

for s in linspace(0.95, 1.05, 7):
cell = cell0 * s
atoms.set_cell((cell))
ene = atoms.get_potential_energy()
traj.write()
See the equation of states tutorial for analysis of the results.
CASTEP
Introduction
ASE Manual, Release 3.6.1.2828
CASTEP 1 is a software package which uses density functional theory to provide a good atomic-level description
of all manner of materials and molecules. CASTEP can give information about total energies, forces and stresses
on an atomic system, as well as calculating optimum geometries, band structures, optical spectra, phonon spectra
and much more. It can also perform molecular dynamics simulations.
The CASTEP calculator interface class offers intuitive access to all CASTEP settings and most results. All
CASTEP specific settings are accessible via attribute access (i.e. calc.param.keyword = ... or
calc.cell.keyword = ...)
Getting Started:
Set the environment variables appropriately for your system.
>>> export CASTEP_COMMAND=’ ... ’
>>> export CASTEP_PP_PATH=’ ... ’
Running the Calculator
The default initialization command for the CASTEP calculator is
class castep.Castep(directory=’CASTEP’, label=’castep’)
To do a minimal run one only needs to set atoms, this will use all default settings of CASTEP, meaning LDA,
singlepoint, etc..
With a generated castep_keywords.py in place all options are accessible by inspection, i.e. tab-completion. This
works best when using ipython. All options can be accessed via calc.param. or calc.cell.
and documentation is printed with calc.param. ? or calc.cell.
?. All options can also be set directly using calc.keyword = ... or calc.KEYWORD =
... or even calc.KeYwOrD or directly as named arguments in the call to the constructor (e.g.
Castep(task=’GeometryOptimization’)).
All options that go into the .param file are held in an CastepParam instance, while all options that go into
the .cell file and don’t belong to the atoms object are held in an CastepCell instance. Each instance can
be created individually and can be added to calculators by attribute assignment, i.e. calc.param = param or
calc.cell = cell.
All internal variables of the calculator start with an underscore (_). All cell attributes that clearly belong into
the atoms object are blocked. Setting calc.atoms_attribute (e.g. = positions) is sent directly to the
atoms object.
1 S. J. Clark, M. D. Segall, C. J. Pickard, P. J. Hasnip, M. J. Probert, K. Refson, M. C. Payne Zeitschrift für Kristallographie 220(5-6)
pp.567- 570 (2005)
7.14. Calculators 131