PwRelaxWorkChain

First, load the AiiDA orm and activate your profile:

from aiida import orm, load_profile

load_profile()

Import the PwRelaxWorkChain and use the protocols to run a structure with the code you have set up:

from ase.build import bulk
from aiida_quantumespresso.workflows.pw.relax import PwRelaxWorkChain

code = orm.load_code('pw@localhost')
structure = orm.StructureData(ase=bulk('Si', 'diamond', 5.4))

builder = PwRelaxWorkChain.get_builder_from_protocol(
    code=code,
    structure=structure,
    protocol='fast'
)

The calculation can then be executed using for example the run function of the engine:

from aiida.engine import run

results = run(builder)

The results will contain the output nodes, for example the output_structure:

results['output_structure'].get_pymatgen()

Define the RelaxType

By default, the get_builder_from_protocol() method will set inputs that instruct Quantum ESPRESSO to optimise both the geometry and cell, i.e.:

• CONTROL.calculation = vc-relax

• CELL.conv_thr = all

In case you want to only optimise the positions, you can specify this using the relax_type input:

from aiida_quantumespresso.common.types import RelaxType

builder = PwRelaxWorkChain.get_builder_from_protocol(
    code=code,
    structure=structure,
    relax_type=RelaxType.POSITIONS
)

Options for RelaxType:

• POSITIONS_CELL: (default) Optimise both the atomic positions and unit cell.

• POSITIONS; Only the atomic positions are relaxed, cell is fixed.

• SHAPE: Only the cell shape is optimized at a fixed volume and fixed atomic positions.

• CELL: Only the cell is optimized, both shape and volume, while atomic positions are fixed.

• POSITIONS_SHAPE: Same as SHAPE but atomic positions are relaxed as well.