Protocol

Protocol#

In the context of this package, a protocol is a set of input parameters used to run a workflow. You can obtain a fully populated builder for each WorkChain by providing one of the three supported protocols to the get_builder_from_protocol() method:

  • fast: low precision calculations at minimal computational cost for testing purposes.

  • balanced: normal precision calculations at moderate computational cost.

  • stringent: high precision calculations at higher computational cost. Recommended for metals with lanthanides/actinides

On this page you can find an overview of the various input parameters that are controlled by protocols and their values.

K-points sampling#

The Brillouin zone is sampled at \(k\)-points that are defined by a Monkhorst-Pack mesh including the \(\Gamma\)-point. The mesh density is defined in terms of the kpoints_distance input, which defined the maximum distance between \(k\)-points in each reciprocal-space direction (i.e., the protocol chooses the smallest \(k\)-point mesh with at least the density required by the specified kpoints_distance). These values correspond to the extensively tested balanced protocol described in detail by Nascimento et al.[1].

Protocol name

Smearing [Ry]

kpoints_distance [1/A]

fast

0.0275

0.30

balanced

0.0200

0.15

stringent

0.0125

0.10

Pseudopotentials#

Pseudopotentials are taken from the Standard Solid-state Pseudopotential (SSSP) library, which collects pseudopotentials from a number of libraries. The SSSP provides a set of rigorously tested values for the recommended wave function and charge density energy cutoffs for each pseudopotential. For every structure, ecutwfc and ecutrho are set to the maximum of the SSSP-recommended values over the elements in its composition.

Protocol name

Pseudos & Cutoffs

fast

SSSP/1.3/PBEsol/efficiency

balanced

SSSP/1.3/PBEsol/efficiency

stringent

SSSP/1.3/PBEsol/precision

Note

As by default in Quantum ESPRESSO the exchange-correlation functional is taken from the pseudopotential files, this also means all protocols use PBEsol.

Thresholds#

The thresholds for electronic and ionic convergence are the following:

  • SCF energy: the energy threshold for self-consistency in the SCF cycle, see conv_thr. The protocol is defined in terms of Ry/atom, i.e. the value of conv_thr is calculated by multiplying the protocol value with the number of atoms.

  • Ionic energy: the energy threshold for convergence in the ionic optimization, see etot_conv_thr. The protocol is defined in terms of Ry/atom, i.e. the value of etot_conv_thr is calculated by multiplying the protocol value with the number of atoms.

  • Forces: the threshold for convergence of the force components, see forc_conv_thr.

Protocol name

SCF energy [Ry/atom]

Ionic energy [Ry/atom]

Forces [Ry/bohr]

fast

4e-10

1e-4

1e-3

balanced

2e-10

1e-5

1e-4

stringent

1e-10

5e-6

5e-5

Magnetism#

Note

See the tutorial on magnetic calculations for an introduction on how to work with magnetism in aiida-quantumespresso.

The get_builder_from_protocol() method supports defining the type of magnetic calculation via the spin_type input:

  • SpinType.NONE: Non-spin-polarised calculation (nspin = 1).

  • SpinType.COLLINEAR: Spin-polarised calculation (nspin = 2). Each kind is initialized in a high-spin ferromagnetic configuration, where elements with partially occupied \(d\) or \(f\) orbitals are assigned a magnetic moment of 5 \(\mu_B\) or 7 \(\mu_B\), respectively. For all other elements, the electrons are initialized to have a 10% surplus in the spin-up channel (starting_magnetization = 0.1).

  • SpinType.NON_COLLINEAR: Non-collinear spin-polarised calculation (noncolin = True, nspin = 4). The size of the magnetic vector (starting_magnetization) is set to the same value as the collinear case, and both angles (angle1 and angle2) are set to zero. We also use the fully relativistic PBEsol pseudopotentials from the Pseudo Dojo (PseudoDojo/0.4/PBEsol/FR/standard/upf family).

  • SpinType.SPIN_ORBIT: Non-collinear spin-polarised calculation including spin-orbit lspinorb. The (starting_magnetization) and angles are initialised using the same approach as for SpinType.NON_COLLINEAR.