Source code for stk.molecular.topology_graphs.topology_graph.optimizers.periodic_collapser

"""
Periodic Collapser
==================

"""

import mchammer as mch

from .optimizer import Optimizer
from .utilities import get_long_bond_ids, get_mch_bonds, get_subunits


[docs]class PeriodicCollapser(Optimizer): """ Performs rigid-body collapse of molecules [1]_. This :class:`.Optimizer` will also update the `.PeriodicInfo`. Examples -------- *Structure Optimization* Using :class:`.PeriodicCollapser` will lead to :class:`.ConstructedMolecule` structures without long bonds and match the unit-cell to the new structure. .. testcode:: structure-optimization import stk bb1 = stk.BuildingBlock('BrCCBr', [stk.BromoFactory()]) bb2 = stk.BuildingBlock('BrCC(CBr)CBr', [stk.BromoFactory()]) topology_graph = stk.cof.PeriodicHoneycomb( building_blocks=(bb1, bb2), lattice_size=(1, 2, 3), optimizer=stk.PeriodicCollapser(), ) cof = stk.ConstructedMolecule(topology_graph) Optimisation with :mod:`stk` simply collects the final position matrix and periodic info. The optimisation's trajectory can be output using the :mod:`MCHammer` implementation if required by the user [1]_. The open-source optimization code :mod:`MCHammer` specializes in the `collapsing` of molecules with long bonds like those constructed by :mod:`stk`. This code is entirely nonphysical and is, therefore, completely general to any chemistry. References ---------- .. [1] https://github.com/andrewtarzia/MCHammer """
[docs] def __init__( self, step_size=0.1, distance_threshold=1.5, scale_steps=False, ): """ Initialize an instance of :class:`.PeriodicCollapser`. Parameters ---------- step_size : :class:`float`, optional The relative size of the step to take during collapse in Angstrom. distance_threshold : :class:`float`, optional Distance between distinct building blocks to use as threshold for halting collapse in Angstrom. scale_steps : :class:`bool`, optional Whether to scale the step of each distinct building block by its relative distance from the molecules centroid. """ self._optimizer = mch.Collapser( step_size=step_size, distance_threshold=distance_threshold, scale_steps=scale_steps, )
[docs] def optimize(self, state): mch_mol = mch.Molecule( atoms=( mch.Atom( id=atom.get_id(), element_string=atom.__class__.__name__, ) for atom in state.get_atoms() ), bonds=get_mch_bonds(state), position_matrix=state.get_position_matrix(), ) mch_mol, result = self._optimizer.get_result( mol=mch_mol, bond_pair_ids=tuple(get_long_bond_ids(state)), subunits=get_subunits(state), ) old_pos_mat = state.get_position_matrix() new_pos_mat = mch_mol.get_position_matrix() old_extents = ( abs(max(old_pos_mat[:, i]) - min(old_pos_mat[:, i])) for i in range(3) ) new_extents = ( abs(max(new_pos_mat[:, i]) - min(new_pos_mat[:, i])) for i in range(3) ) ratios = (n / o for n, o in zip(new_extents, old_extents)) old_lattice = state.get_lattice_constants() new_lattice = tuple( old_lattice[i] * ratio for i, ratio in enumerate(ratios) ) state = state.with_lattice_constants(new_lattice) return state.with_position_matrix( position_matrix=mch_mol.get_position_matrix() )