Adding new calculators
Adding an ASE interface to your favorite force-calculator is very
simple. Take a look at the
Calculator and
FileIOCalculator classes below
(the code is here: ase/calculators/calculator.py). You should
inherit from the FileIOCalculator
and implement the read(),
read_results() and
write_input() methods.
The methods set(),
check_state() and
set_label() may also need
to be implemented.
See also
The code for our Abinit interface: ase/calculators/abinit.py
Description of base-classes
The Calculator base-class
- class ase.calculators.calculator.Calculator(restart=None, ignore_bad_restart_file=<object object>, label=None, atoms=None, directory='.', **kwargs)[source]
Base-class for all ASE calculators.
A calculator must raise PropertyNotImplementedError if asked for a property that it can’t calculate. So, if calculation of the stress tensor has not been implemented, get_stress(atoms) should raise PropertyNotImplementedError. This can be achieved simply by not including the string ‘stress’ in the list implemented_properties which is a class member. These are the names of the standard properties: ‘energy’, ‘forces’, ‘stress’, ‘dipole’, ‘charges’, ‘magmom’ and ‘magmoms’.
Basic calculator implementation.
- restart: str
Prefix for restart file. May contain a directory. Default is None: don’t restart.
- ignore_bad_restart_file: bool
Deprecated, please do not use. Passing more than one positional argument to Calculator() is deprecated and will stop working in the future. Ignore broken or missing restart file. By default, it is an error if the restart file is missing or broken.
- directory: str or PurePath
Working directory in which to read and write files and perform calculations.
- label: str
Name used for all files. Not supported by all calculators. May contain a directory, but please use the directory parameter for that instead.
- atoms: Atoms object
Optional Atoms object to which the calculator will be attached. When restarting, atoms will get its positions and unit-cell updated from file.
- discard_results_on_any_change = False
Whether we purge the results following any change in the set() method.
- set_label(label)[source]
Set label and convert label to directory and prefix.
Examples:
label=’abc’: (directory=’.’, prefix=’abc’)
label=’dir1/abc’: (directory=’dir1’, prefix=’abc’)
label=None: (directory=’.’, prefix=None)
- read(label)[source]
Read atoms, parameters and calculated properties from output file.
Read result from self.label file. Raise ReadError if the file is not there. If the file is corrupted or contains an error message from the calculation, a ReadError should also be raised. In case of succes, these attributes must set:
- atoms: Atoms object
The state of the atoms from last calculation.
- parameters: Parameters object
The parameter dictionary.
- results: dict
Calculated properties like energy and forces.
The FileIOCalculator.read() method will typically read atoms and parameters and get the results dict by calling the read_results() method.
- set(**kwargs)[source]
Set parameters like set(key1=value1, key2=value2, …).
A dictionary containing the parameters that have been changed is returned.
Subclasses must implement a set() method that will look at the chaneged parameters and decide if a call to reset() is needed. If the changed parameters are harmless, like a change in verbosity, then there is no need to call reset().
The special keyword ‘parameters’ can be used to read parameters from a file.
- calculate(atoms=None, properties=['energy'], system_changes=['positions', 'numbers', 'cell', 'pbc', 'initial_charges', 'initial_magmoms'])[source]
Do the calculation.
- properties: list of str
List of what needs to be calculated. Can be any combination of ‘energy’, ‘forces’, ‘stress’, ‘dipole’, ‘charges’, ‘magmom’ and ‘magmoms’.
- system_changes: list of str
List of what has changed since last calculation. Can be any combination of these six: ‘positions’, ‘numbers’, ‘cell’, ‘pbc’, ‘initial_charges’ and ‘initial_magmoms’.
Subclasses need to implement this, but can ignore properties and system_changes if they want. Calculated properties should be inserted into results dictionary like shown in this dummy example:
self.results = {'energy': 0.0, 'forces': np.zeros((len(atoms), 3)), 'stress': np.zeros(6), 'dipole': np.zeros(3), 'charges': np.zeros(len(atoms)), 'magmom': 0.0, 'magmoms': np.zeros(len(atoms))}
The subclass implementation should first call this implementation to set the atoms attribute and create any missing directories.
- calculate_numerical_forces(atoms, d=0.001)[source]
Calculate numerical forces using finite difference.
All atoms will be displaced by +d and -d in all directions.
Deprecated since version 3.24.0.
The FileIOCalculator class
- class ase.calculators.calculator.FileIOCalculator(restart=None, ignore_bad_restart_file=<object object>, label=None, atoms=None, command=None, profile=None, **kwargs)[source]
Base class for calculators that write/read input/output files.
File-IO calculator.
- command: str
Command used to start calculation.
- calculate(atoms=None, properties=['energy'], system_changes=['positions', 'numbers', 'cell', 'pbc', 'initial_charges', 'initial_magmoms'])[source]
Do the calculation.
- properties: list of str
List of what needs to be calculated. Can be any combination of ‘energy’, ‘forces’, ‘stress’, ‘dipole’, ‘charges’, ‘magmom’ and ‘magmoms’.
- system_changes: list of str
List of what has changed since last calculation. Can be any combination of these six: ‘positions’, ‘numbers’, ‘cell’, ‘pbc’, ‘initial_charges’ and ‘initial_magmoms’.
Subclasses need to implement this, but can ignore properties and system_changes if they want. Calculated properties should be inserted into results dictionary like shown in this dummy example:
self.results = {'energy': 0.0, 'forces': np.zeros((len(atoms), 3)), 'stress': np.zeros(6), 'dipole': np.zeros(3), 'charges': np.zeros(len(atoms)), 'magmom': 0.0, 'magmoms': np.zeros(len(atoms))}
The subclass implementation should first call this implementation to set the atoms attribute and create any missing directories.