QuantumESPRESSO Keywords¶

The input to the QuantumESPRESSO engine has a similar structure as the input to the pw.x executable.

Exceptions: The pseudopotentials are specified in the engine Pseudopotentials block. They will then be appended to the ATOMIC_SPECIES lines in the pw.x input.

Note

In the input file there are two System blocks:

The AMS driver System block contains the atomic species, atomic positions, atomic masses (isotopes), and lattice vectors, just like for any other AMS calculation. On each atom line you can also specify for example QE.label=aaa to set the internal QE atom type for that atom. See the Examples.
The QuantumESPRESSO Engine System block contains keywords from the &SYSTEM namelist in the pw.x input file. For example, ecutwfc to set the plane-wave energy cutoff. This block is described in detail below.

Pseudopotentials¶

The pseudopotentials are specified in a free block. See the Examples for examples.

The pseudopotentials will also determine the XC functional used, unless you set the System%input_dft option.

See the list of pseudopotentials that are included with the AMS Quantum ESPRESSO package.

Pseudopotentials # Non-standard block. See details.
   ...
End

Pseudopotentials

Type: Non-standard block
Description: Selects the pseudopotential to use for the atomic species. Each line should contain a symbol followed by a filename (or path relative to $PSEUDO_DIR) or an absolute path to the pseudopotential file.

K-space and k-point sampling¶

K_Points header # Non-standard block. See details.
   ...
End

K_Points

Type: Non-standard block
Description: Specify the used k-points. The type of k-points to use (e.g. automatic or gamma is specified in the header of this block. If this block is absent, only the Gamma point will be used.

Control block¶

Control
   dipfield Yes/No
   lelfield Yes/No
   tefield Yes/No
End

Control

Type: Block
Description: Keywords from the &CONTROL namelist in the QuantumEspresso input file.

dipfield

Type: Bool
Default value: No
Description: If True (and tefield is True). a dipole correction is also added to the bare ionic potential - implements the recipe of L. Bengtsson, PRB 59, 12301 (1999). See keywords edir, emaxpos, eopreg for the form of the correction. Must be used ONLY in a slab geometry, for surface calculations, with the discontinuity FALLING IN THE EMPTY SPACE.

lelfield

Type: Bool
Default value: No
Description: If True a homogeneous finite electric field described through the modern theory of the polarization is applied. This is different from setting tefield to True!

tefield

Type: Bool
Default value: No
Description: If True a saw-like potential simulating an electric field is added to the bare ionic potential. See keywords edir, eamp, emaxpos, eopreg for the form and size of the added potential.

Electrons block¶

Electrons
   conv_thr float
   diagonalization [Davidson | ConjugateGradient | PPCG | ParO | RMM-Davidson | RMM-ParO]
   electron_maxstep integer
   mixing_beta float
   mixing_mode [Plain | Thomas-Fermi | Local-Thomas-Fermi]
   mixing_ndim integer
End

Electrons

Type: Block
Description: Keywords from the &ELECTRONS namelist in the QuantumEspresso input file.

conv_thr

Type: Float
Default value: 1e-06
Unit: Rydberg
GUI name: Convergence threshold
Description: Convergence threshold for selfconsistency: estimated energy error < conv_thr. Note that conv_thr is extensive, like the total energy.

diagonalization

Type: Multiple Choice
Default value: Davidson
Options: [Davidson, ConjugateGradient, PPCG, ParO, RMM-Davidson, RMM-ParO]
Description: Available options are: • Davidson: iterative diagonalization with overlap matrix. Fast, may in some rare cases fail. • ConjugateGradient: Conjugate-gradient-like band-by-band diagonalization. MUCH slower than Davidson but uses less memory and is (a little bit) more robust. • PPCG: PPCG iterative diagonalization • ParO: ParO iterative diagonalization • RMM-Davidson & RMM-ParO: RMM-DIIS iterative diagonalization. To stabilize the SCF loop RMM-DIIS is alternated with calls to Davidson or ParO solvers.

electron_maxstep

Type: Integer
Default value: 100
GUI name: Maximum # SCF iterations
Description: Maximum number of iterations in a SCF step.

mixing_beta

Type: Float
Default value: 0.7
GUI name: Beta
Description: Mixing factor for self-consistency.

mixing_mode

Type: Multiple Choice
Default value: Plain
Options: [Plain, Thomas-Fermi, Local-Thomas-Fermi]
GUI name: Mixing mode
Description: Available options are: • Plain: charge density Broyden mixing • Thomas-Fermi: as above, with simple Thomas-Fermi screening (for highly homogeneous systems) • Local-Thomas-Fermi: as above, with local-density-dependent TF screening (for highly inhomogeneous systems)

mixing_ndim

Type: Integer
Default value: 8
Description: Number of iterations used in mixing scheme. If you are tight with memory, you may reduce it to 4 or so.

System block (in the QuantumESPRESSO engine)¶

System
   assume_isolated [Auto | None | Martyna-Tuckerman]
   degauss float
   dftd3_threebody Yes/No
   dftd3_version [2 | 3 | 4 | 5 | 6]
   eamp float
   ecutfock float
   ecutrho float
   ecutwfc float
   edir [1 | 2 | 3]
   emaxpos float
   eopreg float
   exx_fraction float
   input_dft string
   nspin [None | Collinear | Non-Collinear]
   occupations [Smearing | Tetrahedra | Tetrahedra_lin | Tetrahedra_opt | Fixed]
   smearing [Gaussian | Methfessel-Paxton | Marzari-Vanderbilt | Fermi-Dirac]
   starting_magnetization string
   tot_magnetization float
   vdw_corr [None | Grimme-D2 | Grimme-D3 | TS | MBD | XDM]
   xdm_a1 float
   xdm_a2 float
End

System

Type: Block
Description: Keywords from the &SYSTEM namelist in the QuantumEspresso input file.

assume_isolated

Type: Multiple Choice
Default value: Auto
Options: [Auto, None, Martyna-Tuckerman]
Description: Used to perform calculation assuming the system to be isolated (a molecule or a cluster in a 3D supercell). Currently available choices: • Auto: determines the used method based on the periodicity of the system in the AMS driver input. None for systems 3D periodicity, Martyna-Tuckerman for systems without a lattice. • None: regular periodic calculation w/o any correction. • Martyna-Tuckerman: correction to both total energy and scf potential. Adapted from: G.J. Martyna, and M.E. Tuckerman, A reciprocal space based method for treating long range interactions in ab-initio and force-field-based calculation in clusters, J. Chem. Phys. 110, 2810 (1999), [doi:10.1063/1.477923].

degauss

Type: Float
Default value: 0.0
Unit: Rydberg
GUI name: Smearing width
Description: Value of the gaussian spreading for Brillouin-zone integration in metals.

dftd3_threebody

Type: Bool
Default value: Yes
Description: Turn three-body terms in Grimme-D3 on. If False two-body contributions only are computed, using two-body parameters of Grimme-D3. If dftd3_version is set to 2, three-body contribution is always disabled.

dftd3_version

Type: Multiple Choice
Default value: 3
Options: [2, 3, 4, 5, 6]
Description: Version of Grimme implementation of Grimme-D3: • 2: Original Grimme-D2 parametrization • 3: Grimme-D3 (zero damping) • 4: Grimme-D3 (BJ damping) • 5: Grimme-D3M (zero damping) • 6: Grimme-D3M (BJ damping) • NOTE: not all functionals are parametrized.

eamp

Type: Float
Default value: 0.001
Unit: Hartree
Description: Amplitude of the electric field, in Hartree a.u. = = 51.4220632*10^10 V/m. Used only if tefield is enabled. The saw-like potential increases with slope eamp in the region from (emaxpos``+``eopreg-1) to (emaxpos), then decreases to 0 until (emaxpos``+``eopreg), in units of the crystal vector edir. Important: the change of slope of this potential must be located in the empty region, or else unphysical forces will result.

ecutfock

Type: Float
Unit: Rydberg
GUI name: Exchange operator cutoff
Description: Kinetic energy cutoff for the exact exchange operator in EXX type calculations. By default this is the same as ecutrho but in some EXX calculations, a significant speed-up can be obtained by reducing ecutfock, at the expense of some loss in accuracy. Must be >= ecutwfc. Not implemented for stress calculation and for US-PP and PAW pseudopotentials. Use with care, especially in metals where it may give raise to instabilities.

ecutrho

Type: Float
Unit: Rydberg
GUI name: Density energy cutoff
Description: Kinetic energy cutoff for charge density and potential. Default value is 4*``ecutwfc``. For norm-conserving pseudopotential you should stick to the default value, you can reduce it by a little but it will introduce noise especially on forces and stress. If there are ultrasoft PP, a larger value than the default is often desirable (ecutrho = 8 to 12 times ecutwfc, typically). PAW datasets can often be used at 4*``ecutwfc``, but it depends on the shape of augmentation charge: testing is mandatory. The use of gradient-corrected functional, especially in cells with vacuum, or for pseudopotential without non-linear core correction, usually requires an higher values of ecutrho to be accurately converged.

ecutwfc

Type: Float
Default value: 40.0
Unit: Rydberg
GUI name: Wavefunction energy cutoff
Description: Kinetic energy cutoff for wavefunctions.

edir

Type: Multiple Choice
Options: [1, 2, 3]
Description: The direction of the electric field or dipole correction is parallel to the bg(:,edir) reciprocal lattice vector, so the potential is constant in planes defined by FFT grid points. Used only if tefield is enabled.

emaxpos

Type: Float
Default value: 0.5
Description: Position of the maximum of the saw-like potential along crystal axis edir, within the unit cell (see also eopreg), 0 < emaxpos < 1 Used only if tefield is enabled.

eopreg

Type: Float
Default value: 0.1
Description: Zone in the unit cell where the saw-like potential decreases, see also amp. Must be in range 0 < eopreg < 1. Used only if tefield is enabled.

exx_fraction

Type: Float
GUI name: EXX fraction
Description: Fraction of EXX for hybrid functional calculations. In the case of input_dft set to ‘PBE0’, the default value is 0.25, while for input_dft set to ‘B3LYP’ the exx_fraction default value is 0.20.

input_dft

Type: String
GUI name: Force XC
Description: Exchange-correlation functional: eg ‘PBE’, ‘BLYP’, etc. See Modules/funct.f90 in the QE source code for allowed values. Overrides the value read from pseudopotential files. Use with care and if you know what you are doing!

nspin

Type: Multiple Choice
Default value: None
Options: [None, Collinear, Non-Collinear]
GUI name: Magnetization
Description: Available options are: • None: not spin-polarized • Collinear: LSDA with magnetization along z-axis • Non-Collinear: any magnetization (equivalent to setting the noncolin key to True)

occupations

Type: Multiple Choice
Default value: Fixed
Options: [Smearing, Tetrahedra, Tetrahedra_lin, Tetrahedra_opt, Fixed]
Description: Available options are: • Smearing: gaussian smearing for metals; see keywords smearing and degauss • Tetrahedra: Tetrahedron method, Bloechl’s version: P.E. Bloechl, PRB 49, 16223 (1994). Requires uniform grid of k-points, to be automatically generated (see block K_Points). Well suited for calculation of DOS, less so (because not variational) for force/optimization/dynamics calculations. • Tetrahedra_lin: Original linear tetrahedron method. To be used only as a reference; the optimized tetrahedron method is more efficient. • Tetrahedra_opt: ptimized tetrahedron method, see M. Kawamura, PRB 89, 094515 (2014). Can be used for phonon calculations as well. • Fixed: for insulators with a gap.

smearing

Type: Multiple Choice
Default value: Gaussian
Options: [Gaussian, Methfessel-Paxton, Marzari-Vanderbilt, Fermi-Dirac]
Description: Available options are: • Gaussian: ordinary Gaussian spreading • Methfessel-Paxton: first-order spreading (see PRB 40, 3616 (1989)) • Marzari-Vanderbilt: cold smearing (see PRL 82, 3296 (1999)) • Fermi-Dirac: smearing with Fermi-Dirac function

starting_magnetization

Type: String
Recurring: True
Description: Expects an element symbol (or QE.Label) followed by a real number in the range [-1:+1]. Starting spin polarization for an atomic type in a spin polarized (LSDA or noncollinear/spin-orbit) calculation. Allowed values range between -1 (all spins down for the valence electrons of atom type ‘i’) to 1 (all spins up). If you expect a nonzero magnetization in your ground state, you MUST either specify a nonzero value for at least one atomic type, or constrain the magnetization using keyword tot_magnetization for LSDA, constrained_magnetization for noncollinear/spin-orbit calculations. If you don’t, you will get a nonmagnetic (zero magnetization) state. In order to perform LSDA calculations for an antiferromagnetic state, define two different atomic species corresponding to sublattices of the same atomic type. Note: If you fix the magnetization with tot_magnetization, do not specify starting_magnetization. Note: In the noncollinear/spin-orbit case, starting with zero starting_magnetization on all atoms imposes time reversal symmetry. The magnetization is never calculated and is set to zero.

tot_magnetization

Type: Float
GUI name: Fix total magnetization
Description: Total majority spin charge minus minority spin charge. Used to impose a specific total electronic magnetization. If unspecified then tot_magnetization variable is ignored and the amount of electronic magnetization is determined during the self-consistent cycle.

vdw_corr

Type: Multiple Choice
Default value: None
Options: [None, Grimme-D2, Grimme-D3, TS, MBD, XDM]
GUI name: Dispersion correction
Description: Type of Van der Waals correction. Allowed values: • Grimme-D2: Semiempirical Grimme’s DFT-D2, see S. Grimme, J. Comp. Chem. 27, 1787 (2006) [doi:10.1002/jcc.20495], and V. Barone et al., J. Comp. Chem. 30, 934 (2009) [doi:10.1002/jcc.21112]. • Grimme-D3: Semiempirical Grimme’s DFT-D3, see S. Grimme et al, J. Chem. Phys 132, 154104 (2010) [doi:10.1063/1.3382344]. • TS: Tkatchenko-Scheffler dispersion corrections with first-principle derived C6 coefficients, see A. Tkatchenko and M. Scheffler, PRL 102, 073005 (2009). • MBD: Many-body dipersion (MBD) correction to long-range interactions, see A. Ambrosetti, A. M. Reilly, R. A. DiStasio, A. Tkatchenko, J. Chem. Phys. 140 18A508 (2014). • XDM: Exchange-hole dipole-moment model, see A. D. Becke et al., J. Chem. Phys. 127, 154108 (2007) [doi:10.1063/1.2795701], and A. Otero de la Roza et al., J. Chem. Phys. 136, 174109 (2012) [doi:10.1063/1.4705760]. Note that non-local functionals (eg vdw-DF) are NOT specified here but using the input_dft keyword.

xdm_a1

Type: Float
Default value: 0.6836
Description: Damping function parameter a1 (adimensional). It is NOT necessary to give a value if the functional is one of B86bPBE, PW86PBE, PBE, BLYP. For functionals in this list, the coefficients are given in: http://schooner.chem.dal.ca/wiki/XDM; A. Otero de la Roza, E. R. Johnson, J. Chem. Phys. 138, 204109 (2013) [doi:10.1063/1.4705760]

xdm_a2

Type: Float
Default value: 1.5045
Unit: Angstrom
Description: Damping function parameter a2 (Angstrom). It is NOT necessary to give a value if the functional is one of B86bPBE, PW86PBE, PBE, BLYP. For functionals in this list, the coefficients are given in: http://schooner.chem.dal.ca/wiki/XDM; A. Otero de la Roza, E. R. Johnson, J. Chem. Phys. 138, 204109 (2013) [doi:10.1063/1.4705760]

Hubbard U, DFT+U¶

Note: the Hubbard U (and J) settings are specified in the Quantum ESPRESSO 7.1 format. This format is different compared to earlier versions of Quantum ESPRESSO.

Hubbard header # Non-standard block. See details.
   ...
End

Hubbard

Type: Non-standard block
Description: Specify parameters for DFT+U models. The type of Hubbard projectors to use (e.g. atomic or ortho-atomic is specified in the header of this block. Please refer to the QuantumEspresso manual (e.g. Doc/Hubbard_input.pdf) for details concerning the contents of this block.