Add fermi energy to outputs. This is necessary in order to calculate an effective magnetic field based on the difference between the fermi energy of the spin-up and spin-down channel

Author: t-reents

docs/source/workflows/base/relax/index.rst

@@ -171,6 +171,11 @@ Only ``structure`` and ``engines`` can be specified as a positional argument, al
   The default for this input is the Python value None and, in case of calculations with spin, the None value signals that the implementation should automatically decide an appropriate default initial magnetization.
   The implementation of such choice is code-dependent and described in the supplementary material of the `S. P. Huber et al., npj Comput. Mater. 7, 136 (2021)`_.
 
+
+* ``fixed_total_cell_magnetization``. (Type: Python None or a Python float).
+  The total magnetization of the system for fixed spin moment calculations.
+  Should be a float representing the total magnetization in Bohr magnetons (μB).
+
 .. _relax-ref-wc:
 
 * ``reference_workchain.`` (Type: a previously completed ``RelaxWorkChain``, performed with the same code as the ``RelaxWorkChain`` created by ``get_builder``).

src/aiida_common_workflows/workflows/em.py

@@ -1,4 +1,5 @@
-"""Equation of state workflow that can use any code plugin implementing the common relax workflow."""
+"""Workflow to calculate the energy as a function of fixed total magnetization that can use any code
+plugin implementing the common relax workflow and supports fixed spin-moment calulations."""
 import inspect
 
 from aiida import orm
@@ -96,7 +97,21 @@ def define(cls, spec):
         spec.output_namespace('total_energies', valid_type=orm.Float,
             help='The computed total energy of the relaxed structures at each scaling factor.')
         spec.output_namespace('total_magnetizations', valid_type=orm.Float,
-            help='The fixed total magnetizations that were evaluated.')
+            help='The fixed total magnetizations that were evaluated in mu_B.')
+        spec.output_namespace('fermi_energies_up', valid_type=orm.Float,
+            help=(
+                'The fermi energies of the spin-up channel (at each fixed total magnetization). '
+                'Can be used to compute an effective magnetic field. Otherwise, only meaningful '
+                'in combination with the BandsData that will be added in the future.'
+                )
+        )
+        spec.output_namespace('fermi_energies_down', valid_type=orm.Float,
+            help=(
+                'The fermi energies of the spin-down channel (at each fixed total magnetization). '
+                'Can be used to compute an effective magnetic field. Otherwise, only meaningful '
+                'in combination with the BandsData that will be added in the future.'
+            )
+        )
         spec.exit_code(400, 'ERROR_SUB_PROCESS_FAILED',
             message='At least one of the `{cls}` sub processes did not finish successfully.')
 
@@ -130,7 +145,12 @@ def inspect_em(self):
             energy = child.outputs.total_energy
             total_magnetization = child.outputs.total_magnetization
 
+            fermi_energy_up = child.outputs.fermi_energy_up
+            fermi_energy_down = child.outputs.fermi_energy_down
+
             self.report(f'Image {index}: total_magnetization={total_magnetization}, total energy={energy.value}')
 
             self.out(f'total_energies.{index}', energy)
             self.out(f'total_magnetizations.{index}', total_magnetization)
+            self.out(f'fermi_energies_up.{index}', fermi_energy_up)
+            self.out(f'fermi_energies_down.{index}', fermi_energy_down)

src/aiida_common_workflows/workflows/relax/quantum_espresso/workchain.py

@@ -9,6 +9,8 @@
 
 __all__ = ('QuantumEspressoCommonRelaxWorkChain',)
 
+OPTIONAL_OUTPUT_PORTS = ['total_magnetization', 'fermi_energy', 'fermi_energy_up', 'fermi_energy_down']
+
 
 @calcfunction
 def extract_from_trajectory(trajectory):
@@ -30,12 +32,12 @@ def extract_from_trajectory(trajectory):
 def extract_from_parameters(parameters):
     """Return the total energy and optionally the total magnetization from the given parameters node."""
     total_energy = parameters.base.attributes.get('energy')
-    total_magnetization = parameters.base.attributes.get('total_magnetization', None)
 
     results = {'total_energy': orm.Float(total_energy)}
 
-    if total_magnetization is not None:
-        results['total_magnetization'] = orm.Float(total_magnetization)
+    for output_name in OPTIONAL_OUTPUT_PORTS:
+        if output_name in parameters.base.attributes:
+            results[output_name] = orm.Float(parameters.base.attributes.get(output_name))
 
     return results
 
@@ -50,20 +52,18 @@ def convert_outputs(self):
         """Convert the outputs of the sub workchain to the common output specification."""
         outputs = self.ctx.workchain.outputs
 
-        result = extract_from_parameters(outputs.output_parameters).values()
+        results = extract_from_parameters(outputs.output_parameters)
         forces, stress = extract_from_trajectory(outputs.output_trajectory).values()
 
-        try:
-            total_energy, total_magnetization = result
-        except ValueError:
-            total_energy, total_magnetization = next(iter(result)), None
+        total_energy = results.get('total_energy')
 
         if 'output_structure' in outputs:
             self.out('relaxed_structure', outputs.output_structure)
 
-        if total_magnetization is not None:
-            self.out('total_magnetization', total_magnetization)
-
         self.out('total_energy', total_energy)
         self.out('forces', forces)
         self.out('stress', stress)
+
+        for output_name in OPTIONAL_OUTPUT_PORTS:
+            if output_name in results:
+                self.out(output_name, results[output_name])

src/aiida_common_workflows/workflows/relax/workchain.py

@@ -48,6 +48,26 @@ def define(cls, spec):
             help='All cell dimensions and atomic positions are in Ångstrom.')
         spec.output('total_energy', valid_type=Float, required=False,
             help='Total energy in eV.')
+        spec.output('fermi_energy', valid_type=Float, required=False,
+            help=(
+                'Fermi energy in eV. The value is only present for non-magnetic '
+                'or non-collinear magnetic calculations. In case of collinear '
+                'magnetic calculations, the fermi energies for spin up and down '
+                'are.'
+            )
+        )
+        spec.output('fermi_energy_down', valid_type=Float, required=False,
+            help=(
+                'Fermi energy for spin down channel in eV. Only returned for '
+                'collinear magnetic calculations.'
+                )
+        )
+        spec.output('fermi_energy_up', valid_type=Float, required=False,
+            help=(
+                'Fermi energy for spin up channel in eV. Only returned for '
+                'collinear magnetic calculations.'
+            )
+        )
         spec.output('total_magnetization', valid_type=Float, required=False,
             help='Total magnetization in Bohr magnetons.')
         spec.output('remote_folder', valid_type=RemoteData, required=False,