assyst package¶

Submodules¶

assyst.crystals module¶

Crystal structure generation step of ASSYST.

class assyst.crystals.Formulas(atoms: tuple[dict[str, int], ...])¶

Bases: Sequence

Simple helper to generate lists of structure compositions.

sample_space_groups() is the intended consumer and expects an iterable of dictionaries, where each dictionary maps an element name to the number of atoms of this type in one structure. Formulas behaves as if it were such a tuple, but extends the basic python arithmetic operations to make building the list a bit simpler.

The class can be initialized from any tuple of dictionaries.

>>> el_manual = Formulas(({'Cu': 1}, {'Cu': 2}))

range() is a helper class method that initializes Formulas for a single element and takes the same arguments as the builtin range, except that it skips the zero.

>>> el = Formulas.range('Cu', 3)
Formulas(atoms=({'Cu': 1}, {'Cu': 2}))
>>> el == el_manual
True

Addition is overloaded to the addition of the underlying tuples.

>>> Formulas.range('Cu', 1, 5) == Formulas.range('Cu', 1, 3) + Formulas.range('Cu', 3, 5)

The bitwise or operation is akin to the inner product

>>> Formulas.range('Cu', 3) | Formulas.range('Ag', 3)
Formulas(atoms=({'Cu': 1, 'Ag': 1}, {'Cu': 2, 'Ag': 2}))

>>> Formulas.range('Cu', 3) * Formulas.range('Ag', 3)
Formulas(atoms=({'Cu': 1, 'Ag': 1}, {'Cu': 2, 'Ag': 1}, {'Cu': 1, 'Ag': 2}, {'Cu': 2, 'Ag': 2}))

atoms: tuple[dict[str, int], ...]¶

property elements: set[str]¶: Set of elements present in elements.

classmethod range(elements: str | Iterable[str], *range_args) → Self¶

Creates formulas with number of atoms as given by the builtin range.

Multiple elements are combined as the outer product.

trim(min_atoms: int = 1, max_atoms: int | None = None) → Self¶: Returns a copy of itself with formulas with lesser or more atoms than given limits removed.

assyst.crystals.pyxtal(group: int | list[int], species: tuple[str], num_ions: tuple[int], dim: Literal[1, 2, 3] = 3, repeat: int = 1, allow_exceptions: bool = True, **kwargs) → Atoms | list[dict]¶

Generate random crystal structures with PyXtal.

group must be between 1 and the largest possible value for the given dimensionality:: dim=3 => 1 - 230 (space groups) dim=2 => 1 - 80 (layer groups) dim=1 => 1 - 75 (rod groups) dim=0 => 1 - 58 (point groups)

When group is passed as a list of integers or repeat>1, generate multiple structures and return them in a list of dicts containing the keys atoms, symmetry and repeat for the ASE structure, the symmetry group number and which iteration it is, respectively.

Parameters:

group (list of int, or int) – the symmetry group to generate or a list of them
species (tuple of str) – which species to include, defines the stoichiometry together with num_ions
num_ions (tuple of int) – how many of each species to include, defines the stoichiometry together with species
dim (int) – dimensionality of the symmetry group, 0 is point groups, 1 is rod groups, 2 is layer groups and 3 is space groups
repeat (int) – how many random structures to generate
allow_exceptions (bool) – when generating multiple structures, silence errors when the requested stoichiometry and symmetry group are incompatible
**kwargs – passed to pyxtal.pyxtal function verbatim

Returns:

the generated structure, if repeat==1 and only one symmetry group is requested list of dict of all generated structures, if repeat>1 or multiple symmetry groups are requested

Return type:

Atoms

Raises:

ValueError – if species and num_ions are not of the same length
ValueError – if stoichiometry and symmetry group are incompatible and allow_exceptions==False or only one structure is requested

assyst.crystals.sample_space_groups(formulas: Formulas | Iterable[dict[str, int]], spacegroups: list[int] | tuple[int, ...] | Iterable[int] | None = None, min_atoms: int = 1, max_atoms: int = 10, max_structures: int | None = None, dim: Literal[0, 1, 2, 3] = 3, tolerance: Literal['metallic', 'atomic', 'molecular', 'vdW'] | DistanceFilter | dict = 'metallic') → Iterator[Atoms]¶

Create symmetric random structures.

Parameters:

formulas (Formulas or iterable of dicts from str to int) – list of chemical formulas
spacegroups (list of int) – which space groups to generate
min_atoms (int) – do not generate structures smaller than this
max_atoms (int) – do not generate structures larger than this
max_structures (int) – generate at most this many structures
dim (one of 0, 1, 2, or 3) – the dimensionality of the structures to generate; if lower than 3 the code generates samples no longer from space groups, but from the subperiodic layer, rod, or point groups.
tolerance (str, dict of elements to radii) – specifies minimum allowed distances between atoms in generated structures; if str then it should be one values understood by pyxtal.tolerace.Tol_matrix; if dict each value gives the minimum radius allowed for an atom, whether a given distance is allowed then depends on the sum of the radii of the respective elements

Yields:

Atoms – random symmetric crystal structures

assyst.relax module¶

Relaxation step of ASSYST.

class assyst.relax.CellRelax(max_steps: int = 100, force_tolerance: float = 0.001, algorithm: Literal['LBFGS'] = 'LBFGS')¶

Bases: Relax

Minimize energy while keeping relative positions and volume constant.

apply_filter_and_constraints(structure: Atoms)¶: Hook to allow subclasses to add filters and constraints.

class assyst.relax.FullRelax(max_steps: int = 100, force_tolerance: float = 0.001, algorithm: Literal['LBFGS'] = 'LBFGS', pressure: float = 0.0)¶

Bases: Relax

Minimize energy with respect to internal positions and cell without constraints.

apply_filter_and_constraints(structure: Atoms)¶: Hook to allow subclasses to add filters and constraints.

pressure: float = 0.0¶

class assyst.relax.Relax(max_steps: int = 100, force_tolerance: float = 0.001, algorithm: Literal['LBFGS'] = 'LBFGS')¶

Bases: object

Minimize energy with respect to internal positions.

Also used as a base class for all other relaxation.

algorithm: Literal['LBFGS'] = 'LBFGS'¶

apply_filter_and_constraints(structure: Atoms)¶: Hook to allow subclasses to add filters and constraints.

force_tolerance: float = 0.001¶

max_steps: int = 100¶

relax(structure: Atoms) → Atoms¶

Relax a structure and return result.

Structure must have a calculator attached. Returned structure will have a SinglePointCalculator with the final energy, forces and stresses attached.

Parameters:: structure (ase.Atoms) – structure to relax
Returns:: relaxed structure with attached single point calculator.
Return type:: ase.Atoms

class assyst.relax.SymmetryRelax(max_steps: int = 100, force_tolerance: float = 0.001, algorithm: Literal['LBFGS'] = 'LBFGS', pressure: float = 0.0)¶

Bases: Relax

Minimize energy with respect to internal positions and cell, while keeping space group fixed.

apply_filter_and_constraints(structure: Atoms)¶: Hook to allow subclasses to add filters and constraints.

pressure: float = 0.0¶

class assyst.relax.VolumeRelax(max_steps: int = 100, force_tolerance: float = 0.001, algorithm: Literal['LBFGS'] = 'LBFGS', pressure: float = 0.0)¶

Bases: Relax

Minimize energy while keeping relative positions and cell shape constant.

apply_filter_and_constraints(structure: Atoms)¶: Hook to allow subclasses to add filters and constraints.

pressure: float = 0.0¶

assyst.relax.relax(settings: Relax, calculator: AseCalculatorConfig | Calculator, structure: Iterable[Atoms]) → Iterator[Atoms]¶

Relax structures according the given relaxation settings.

Output structures have the final energy and force attached as ase’s SinglePointCalculator.

Parameters:

settings (Relax) – the kind of relaxation to perform (position, volume, etc.)
calculator (AseCalculatorConfig or ase.calculators.calculator.Calculator) – the energy/force engine to use
structure (iterable of ase.Atoms) – the structures to minimize

Yields:

ase.Atoms – the corresponding relaxed configuration to each input structure

assyst.perturbations module¶

Classes to apply (random) perturbations to structures.

class assyst.perturbations.PerturbationABC¶

Bases: ABC

Apply some perturbation to a given structure.

class assyst.perturbations.RandomChoice(choice_a: Callable[[Atoms], Atoms] | PerturbationABC, choice_b: Callable[[Atoms], Atoms] | PerturbationABC, chance: float)¶

Bases: PerturbationABC

Apply either of two alternatives randomly.

chance: float¶: Probability to pick choice b

choice_a: Callable[[Atoms], Atoms] | PerturbationABC¶

choice_b: Callable[[Atoms], Atoms] | PerturbationABC¶

class assyst.perturbations.Rattle(sigma: float, create_supercells: bool = False)¶

Bases: PerturbationABC

Displace atoms by some absolute amount from a normal distribution.

create_supercells: bool = False¶: Create minimal 2x2x2 super cells when applied to structures of only one atom.

sigma: float¶

class assyst.perturbations.Series(perturbations: tuple[Callable[[Atoms], Atoms] | PerturbationABC, ...])¶

Bases: PerturbationABC

Apply some perturbations in sequence.

perturbations: tuple[Callable[[Atoms], Atoms] | PerturbationABC, ...]¶

class assyst.perturbations.Stretch(hydro: float, shear: float, minimum_strain: float = 0.001)¶

Bases: PerturbationABC

Apply random cell perturbation.

hydro: float¶

minimum_strain: float = 0.001¶

shear: float¶

assyst.perturbations.apply_perturbations(structures: Iterable[Atoms], perturbations: Iterable[Callable[[Atoms], Atoms] | PerturbationABC], filters: Iterable[Callable[[Atoms], bool] | FilterBase] | Callable[[Atoms], bool] | FilterBase | None = None, retries: int = 10) → Iterator[Atoms]¶

Apply a list of perturbations to each structure and yield the result of each perturbation separately.

If a perturbation raises ValueError it is ignored.

Parameters:

structures – Atomic structures to perturb.
perturbations – Functions that modify structures.
filters – Functions to filter valid results (optional).
retries – Max attempts per perturbation (default: 10).

Yields:

Perturbed structure that passes all filters.

assyst.perturbations.rattle(structure: Atoms, sigma: float) → Atoms¶

Randomly displace positions with gaussian noise.

Operates INPLACE.

assyst.perturbations.stretch(structure: Atoms, hydro: float, shear: float, minimum_strain=0.001) → Atoms¶

Randomly stretch cell with uniform noise.

Ensures at least minimum_strain strain to avoid structures very close to their original structures. These don’t offer a lot of new information and can also confuse VASP’s symmetry analyzer.

Operates INPLACE.

assyst.filters module¶

Classes that filter structures according to some criteria.

The code in the other modules that uses them is set up such that simple functions can always be passed as well and that the classes here are just for convenience.

class assyst.filters.AndFilter(l: Callable[[Atoms], bool] | FilterBase, r: Callable[[Atoms], bool] | FilterBase)¶

Bases: FilterBase

Conjunction of two filters.

l: Callable[[Atoms], bool] | FilterBase¶

r: Callable[[Atoms], bool] | FilterBase¶

class assyst.filters.AspectFilter(maximum_aspect_ratio: float = 6)¶

Bases: FilterBase

Filters structures with high aspect ratios.

maximum_aspect_ratio: float = 6¶

class assyst.filters.CalculatorFilter(*, missing: Literal['error', 'ignore'] = 'error')¶

Bases: FilterBase

Filters that require a single point calculator set on the structure.

missing: Literal['error', 'ignore'] = 'error'¶: What to do when a structure has no (correct) calculator attached.

class assyst.filters.DistanceFilter(radii: dict[str, float])¶

Bases: FilterBase

Filter structures that contain too close atoms.

Setting a radius to NaN allows all bonds involving this atom.

radii: dict[str, float]¶

to_tol_matrix(prototype: Literal['metallic', 'atomic', 'molecular', 'vdW'] = 'metallic') → Tol_matrix¶

Returns equivalent tolerance matrix for pyxtal.

Parameters:: prototype (metallic, atomic, molecular or vdW) – passed to Tol_matrix as is and used there to initialize radii of elements not explicitly set in this filter

class assyst.filters.EnergyFilter(min_energy: float = -inf, max_energy: float = inf, *, missing: Literal['error', 'ignore'] = 'error')¶

Bases: CalculatorFilter

Filters structures by energy per atom.

max_energy: float = inf¶

min_energy: float = -inf¶

class assyst.filters.FilterBase¶

Bases: ABC

Base class for filter objects that implements conjunction and disjunction operators.

class assyst.filters.ForceFilter(max_force: float = inf, *, missing: Literal['error', 'ignore'] = 'error')¶

Bases: CalculatorFilter

Filters structures by maximum force magnitude.

max_force: float = inf¶

class assyst.filters.OrFilter(l: Callable[[Atoms], bool] | FilterBase, r: Callable[[Atoms], bool] | FilterBase)¶

Bases: FilterBase

Disjunction of two filters.

l: Callable[[Atoms], bool] | FilterBase¶

r: Callable[[Atoms], bool] | FilterBase¶

class assyst.filters.VolumeFilter(maximum_volume_per_atom: float)¶

Bases: FilterBase

Filters structures by volume.

maximum_volume_per_atom: float¶

assyst.calculators module¶

Convenience shorts to create ASE calculators to be used inside ASSYST.

Exists mostly to avoid passing around potentially large and unpickle-able calculator objects.

class assyst.calculators.AseCalculatorConfig¶

Bases: ABC

Base class to keep calculator configurations.

abstractmethod get_calculator() → Calculator¶

Return the actual calculator object.

Returns:: the actually usable calculator
Return type:: ase.calculators.calculator.Calculator

class assyst.calculators.Grace(model: str = 'GRACE-FS-OAM')¶

Bases: AseCalculatorConfig

Universal Graph Atomic Cluster Expansion models.

Attention

This class needs additional dependencies! Install tensorpotential from PyPI.

get_calculator() → Calculator¶

Return the actual calculator object.

Returns:: the actually usable calculator
Return type:: ase.calculators.calculator.Calculator

model: str = 'GRACE-FS-OAM'¶

class assyst.calculators.Morse(epsilon: float = 1.0, r0: float = 1.0, rho0: float = 1.0)¶

Bases: AseCalculatorConfig

Morse potential for testing. Parameters as in ASE.

epsilon: float = 1.0¶

get_calculator() → Calculator¶

Return the actual calculator object.

Returns:: the actually usable calculator
Return type:: ase.calculators.calculator.Calculator

r0: float = 1.0¶

rho0: float = 1.0¶

assyst.plot module¶

Helper plotting functions.

assyst.plot.concentration_histogram(structures: list[Atoms], elements: Iterable[str] | None = None, **kwargs)¶

Plot histogram of concentrations.

Parameters:

structures (list of ase.Atoms) – structures to plot
elements (iterable of str) – which element concentrations to plot, by default all present
**kwargs – passed through to matplotlib.pyplot.bar

assyst.plot.distance_histogram(structures: list[Atoms], rmax: float = 6.0, reduce: Literal['min', 'mean'] | Callable[[Iterable[float]], float] | None = 'min', **kwargs)¶

Plot histogram of per-atom volumes.

Parameters:

structures (list of ase.Atoms) – structures to plot
rmax (float) – maximum cutoff to consider neighborhood
reduce (callable from array of floats to float) – applied to the neighbor distances per structure, and should reduce a single scalar that is binned
**kwargs – passed through to matplotlib.pyplot.hist

Returns:

Return value of matplotlib.pyplot.hist

assyst.plot.energy_volume(structures: list[Atoms], **kwargs)¶

Plot energy per atom versus volume per atom.

Requires that ase.calculators.SinglePointCalculator are attached to the atoms, either from a relaxation for final training set calculation.

Parameters:: structure – list[Atoms], structures to plot

assyst.plot.size_histogram(structures: list[Atoms], **kwargs)¶

Plot histogram of number of atoms.

Parameters:

structures (list of ase.Atoms) – structures to plot
**kwargs – passed through to matplotlib.pyplot.hist

Returns:

Return value of matplotlib.pyplot.hist

assyst.plot.volume_histogram(structures: list[Atoms], **kwargs)¶

Plot histogram of per-atom volumes.

Parameters:

structures (list of ase.Atoms) – structures to plot
**kwargs – passed through to matplotlib.pyplot.hist

Returns:

Return value of matplotlib.pyplot.hist

assyst package¶

Submodules¶

assyst.crystals module¶

assyst.relax module¶

assyst.perturbations module¶

assyst.filters module¶

assyst.calculators module¶

assyst.plot module¶

Module contents¶