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paw input variables

This document lists and provides the description of the name (keywords) of the paw input variables to be used in the input file for the abinit executable.

bxctmindg

Mnemonics: BoX CuT-off MINimum for the Double Grid (PAW)
Mentioned in topic(s): topic_PAW
Variable type: real
Dimensions: scalar
Default value: 2.0
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

The box cut-off ratio is the ratio between the wavefunction plane wave sphere radius, and the radius of the sphere that can be inserted in the FFT box, in reciprocal space.

If the density was generated only from wavefunctions, this ratio should be at least two in order for the density to be exact. If one uses a smaller ratio, one will gain speed, at the expense of accuracy. In case of pure ground state calculation (e.g. for the determination of geometries), this is sensible. However, the wavefunctions that are obtained CANNOT be used for starting response function calculation.

However, some augmentation charge is always added in PAW, and even with the box cut-off ratio larger than two, the density is never exact. Sometimes, this ratio must be much larger than two for the computation to be converged at the required level of accuracy.

dmatpawu

Mnemonics: initial Density MATrix for PAW+U
Mentioned in topic(s): topic_DFT+U, topic_ElecDOS
Variable type: real
Dimensions: (2*max(lpawu)+1,2*max(lpawu)+1,max(nsppol, nspinor),%natpawu)
Default value: -10.0
*Only relevant if: %usepaw == 1 and usepawu == 1 and usedmatpu != 0
Added in version: before_v9

Test list (click to open). Moderately used, [16/1245] in all abinit tests, [2/159] in abinit tutorials

For Ground state calculations only. Gives the value of an initial density matrix used in DFT+U and kept fixed during the first abs(usedmatpu) SCF iterations. Only components corresponding to lpawu angular momentum are requested. Restriction: In order to use dmatpawu, lpawu must be identical for all atom types (or -1).

The occupation matrix is in the basis of real spherical harmonics Slm (note that this differs from the choice made when prtdosm = 1, that is in the basis of complex spherical harmonics). They are ordered by increasing m, and are defined e.g. in [Blancoa1997]. For the case l=2 (d states), the five columns corresponds respectively to (the normalisation factor has been dropped)

  • m=-2, \(xy\)
  • m=-1, \(yz\)
  • m=0, \(3z^{2}-r^{2}\)
  • m=1, \(xz\)
  • m=2, \(x^{2}-y^{2}\)

dmatpawu must always be given as a “spin-up” occupation matrix (and if needed a “spin-down” matrix). Be aware that its physical meaning depends on the magnetic properties imposed to the system (with nsppol, nspinor, nspden):

  • Non-magnetic system (nsppol = 1, nspinor = 1, nspden = 1): One (2lpawu+1)x(2lpawu+1) dmatpawu matrix is given for each atom on which +U is applied. It contains the “spin-up” occupations.

  • Ferromagnetic spin-polarized (collinear) system (nsppol = 2, nspinor = 1, nspden = 2): Two (2lpawu+1)x(2lpawu+1) dmatpawu matrices are given for each atom on which +U is applied. They contain the “spin-up” and “spin-down” occupations.

  • Anti-ferromagnetic spin-polarized (collinear) system (nsppol = 1, nspinor = 1, nspden = 2): One (2lpawu+1)x(2lpawu+1) dmatpawu matrix is given for each atom on which +U is applied. It contains the “spin-up” occupations.

  • Non-collinear magnetic system (nsppol = 1, nspinor = 2, nspden = 4): Two (2lpawu+1)x(2lpawu+1) dmatpawu matrices are given for each atom on which +U is applied. They contains the “spin-up” and “spin-down” occupations (defined as n_up=(n+|m|)/2 and n_dn=(n-|m|)/2), where m is the integrated magnetization vector). The direction of the magnetization (which is also the direction of n_up and n_dn) is given by spinat. _Warning: unlike collinear case, atoms having the same magnetization magnitude with different directions must be given the same occupation matrix; the magnetization will be oriented by the value of spinat (this is the case for antiferro-magnetism). _

  • Non-collinear magnetic system with zero magnetization (nsppol = 1, nspinor = 2, nspden = 1): Two (2lpawu+1)x(2lpawu+1) dmatpawu matrices are given for each atom on which +U is applied. They contain the “spin-up” and “spin-down” occupations; But, as “spin-up” and “spin-down” are constrained identical, the “spin-down” one is ignored by the code.

dmatpuopt

Mnemonics: Density MATrix for PAW+U OPTion
Mentioned in topic(s): topic_DFT+U
Variable type: integer
Dimensions: scalar
Default value: 2
Only relevant if: %usepaw == 1 and usepawu == 1
Added in version: before_v9

Test list (click to open). Moderately used, [53/1245] in all abinit tests, [4/159] in abinit tutorials

This option governs the way occupations of localized atomic levels are computed:

  • dmatpuopt = 1: atomic occupations are projections on atomic orbitals (Eq. (6) of [Amadon2008a]).

  • dmatpuopt = 2: atomic occupations are integrated values in PAW spheres of angular-momentum-decomposed charge densities (Eq. (7) of [Amadon2008a]).

  • dmatpuopt = 3: only for tests

  • dmatpuopt = 4: Extrapolations of occupancies outside the PAW-sphere. This Definition gives normalized operator for occupation.

In the general case dmatpuopt = 2 is suitable. The use of dmatpuopt = 1 is restricted to PAW datasets in which the first atomic wavefunction of the correlated subspace is a normalized atomic eigenfunction.

dmatudiag

Mnemonics: Density MATrix for paw+U, DIAGonalization
Mentioned in topic(s): topic_DFT+U
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1 and usepawu == 1 and nspden != 4
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

Relevant only for Ground-State calculations. This option can be used to diagonalize the occupation matrix Nocc_{m,m_prime}. Relevant values are:

  • 0: deactivated.
  • 1: occupation matrix is diagonalized and printed in log file at each SCF cycle (eigenvectors are also given in the log file).
  • 2: for testing purpose.

f4of2_sla

Mnemonics: F4 Over F2 ratio of Slater integrals
Mentioned in topic(s): topic_DFT+U
Variable type: real
Dimensions: scalar
Default value: 0.625 if d electrons, 0.6681 if f electrons, 0 otherwise.

Only relevant if: %usepaw == 1 and (usepawu == 1 or usedmft == 1)
Added in version: before_v9

Test list (click to open). Moderately used, [14/1245] in all abinit tests, [1/159] in abinit tutorials

This gives the ratio of Slater Integrals F4 and F2. It is used in DFT+U or DFT+DMFT for the calculation of the orbital dependent screened coulomb interaction.

f6of2_sla

Mnemonics: F6 Over F2 ratio of Slater integrals
Mentioned in topic(s): topic_DFT+U
Variable type: real
Dimensions: scalar
Default value: 0.4943
Only relevant if: (usepawu == 1 or usedmft == 1) and lpawu == 3
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

Gives the ratio of Slater Integrals F6 and F2. It is used with f4of2_sla == 3 in DFT+U or DFT+DMFT for the calculation of the orbital dependent screened coulomb interaction.

iboxcut

Mnemonics: Integer governing the internal use of BOXCUT - not a very good choice of variable name
Mentioned in topic(s): topic_TuningSpeedMem
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

Concern all summations in the reciprocal space and is allowed in PAW and norm-conserving.

  • if set to 0 all reciprocal space summations are done in a sphere contained in the FFT box.
  • if set to 1 all reciprocal space summations are done in the whole FFT box (useful for tests).

jpawu

Mnemonics: value of J for PAW+U
Characteristics: ENERGY
Mentioned in topic(s): topic_DFT+U
Variable type: real
Dimensions: (ntypat)
Default value: 0
*Only relevant if: %usepaw == 1 and usepawu == 1
Added in version: before_v9

Test list (click to open). Moderately used, [56/1245] in all abinit tests, [7/159] in abinit tutorials

Gives the value of the screened exchange interaction between correlated electrons corresponding to lpawu for each species. In the case where lpawu =-1, the value is not used.

lambsig

Mnemonics: LAMB shielding SIGma
Mentioned in topic(s): topic_NMR, topic_MagField
Variable type: real
Dimensions: (ntypat)
Default value: 0
*Added in version: v9

Test list (click to open). Rarely used, [7/1245] in all abinit tests, [1/159] in abinit tutorials

Chemical shielding at each nucleus due to the core electrons. This quantity is input as an array of values, one for each type, see ntypat. In calculations where the orbital magnetic moment is requested in the presence of a nuclear magnetic dipole moment (see orbmag and nucdipmom), the effect of this shielding will be included. If a PAW dataset is used where this quantity is included, then a non-zero value in lambsig will override the PAW value. The value to be used here can be obtained from the PAW core wavefunctions and the Lamb formula [Abragam1961].

ldaminushalf

Mnemonics: LDA minus half
Mentioned in topic(s): topic_LDAminushalf
Variable type: integer
Dimensions: (ntypat)
Default value: 0
*Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

For each type of atom, gives whether a LDA-\({\frac{1}{2}}\) calculation is to be performed. ldaminushalf =0: the LDA-\(\frac{1}{2}\) approach is not used. ldaminushalf =1: the LDA-\(\frac{1}{2}\) approach is used.

lexexch

Mnemonics: value of angular momentum L for EXact EXCHange
Mentioned in topic(s): topic_xc
Variable type: integer
Dimensions: (ntypat)
Default value: -1
Only relevant if: useexexch == 1
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

Give for each species the value of the angular momentum on which to apply the exact exchange correction.

lpawu

Mnemonics: value of angular momentum L for PAW+U
Mentioned in topic(s): topic_DFT+U
Variable type: integer
Dimensions: (ntypat)
Default value: -1
*Only relevant if: usepawu == 1 or 2
Added in version: before_v9

Test list (click to open). Moderately used, [62/1245] in all abinit tests, [7/159] in abinit tutorials

Give for each species the value of the angular momentum on which to apply the DFT+U correction.

  • If equal to 1 (p-orbitals), 2 (d-orbitals) or 3 (f-orbitals), values of upawu and jpawu are used in the calculation.
  • If equal to -1: do not apply DFT+U correction on the species.

mqgriddg

Mnemonics: Maximum number of Q-wavevectors for the 1-dimensional GRID for the Double Grid in PAW
Characteristics: DEVELOP
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 3001
Added in version: before_v9

Test list (click to open). Rarely used, [7/1245] in all abinit tests, [1/159] in abinit tutorials

Maximum number of wavevectors used to sample the local part of the potential, in PAW. Actually referred to as mqgrid_vl internally. Should change name to the latter. See also mqgrid.

ngfftdg

Mnemonics: Number of Grid points for Fast Fourier Transform: Double Grid
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: (3)
Default value: [0, 0, 0]
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Moderately used, [31/1245] in all abinit tests, [0/159] in abinit tutorials

This variable has the same meaning as ngfft (gives the size of fast Fourier transform (fft) grid in three dimensions) but concerns the “double grid” only used for PAW calculations.

nucefg

Mnemonics: NUClear site Electric Field Gradient
Mentioned in topic(s): topic_EFG
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [8/1245] in all abinit tests, [1/159] in abinit tutorials

If nonzero, calculate the electric field gradient at each atomic site in the unit cell. Values will be written to the main output file (search for Electric Field Gradient). If nucefg=1, the electric field gradient in both atomic units and SI units is given, showing separate contributions from the valence electrons, the ion cores, and the PAW reconstruction. If nucefg=2, the quadrupole couplings to the nuclear electric quadrupole moments are reported as well, and are based on the input values of quadmom. If nucefg=3, then in addition to the nucefg=2 output, the EFGs are computed using an ionic point charge model. This is useful for comparing the accurate PAW-based results to those of simple ion-only models. Use of nucefg=3 requires that the variable ptcharge be set as well. The option nucefg is compatible with spin polarized calculations (see nspden) and also DFT+U (see usepawu).

nucfc

Mnemonics: NUClear site Fermi Contact term
Mentioned in topic(s): topic_EFG
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [5/1245] in all abinit tests, [2/159] in abinit tutorials
  • If set to 1, print the Fermi contact interaction at each nuclear site, that is, the electron density at each site. The result appears in the main output file (search for FC). Note that this calculation is different than what is done by cut3d, because it also computes the PAW on-site corrections in addition to the contribution from the valence pseudo-wavefunctions.

optdcmagpawu

Mnemonics: OPTion for Double-Counting MAGnetic term in PAW+U formalism
Mentioned in topic(s): topic_DFT+U
Variable type: integer
Dimensions: scalar
Default value: 3
Only relevant if: %usepaw == 1, usepawu == 1 or 4, and nspden == 4
Added in version: 9.8.2

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

This option is usefull only for tests and code comparisons. For magnetic computations (nspden==4), it defines how the magnetism is treated in the double counting term in the PAW+U formalism. Abinit versions before 9.8 correspond to optdcmagpawu =1, without magnetism in the DC term, while optdcmagpawu =3 takes into account magnetism in the DC term, that is currently the default.

pawcpxocc

Mnemonics: PAW - use ComPleX rhoij OCCupancies
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 2 if optdriver == 0 and ionmov < 6 and pawspnorb == 1 and iscf >= 10 and (kptopt !=1 or kptopt!=2) and %usepaw == 1, 1 otherwise.

Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [10/1245] in all abinit tests, [1/159] in abinit tutorials

The only possible values for pawcpxocc are 1 or 2. When pawcpxocc == 1, “direct” decomposition of total energy cannot be printed out. When pawcpxocc == 2, PAW augmentation occupancies are treated as COMPLEX; else they are considered as REAL. This is needed when time-reversal symmetry is broken (typically when spin- orbit coupling is activated).

Note for ground-state calculations (optdriver == 0): The imaginary part of PAW augmentation occupancies is only used for the computation of the total energy by “direct scheme”; this is only necessary when SCF mixing on potential is chosen (iscf <10). When SCF mixing on density is chosen (iscf >= 10), the “direct” decomposition of energy is only printed out without being used. It is thus possible to use pawcpxocc = 1 in the latter case. In order to save CPU time, when molecular dynamics is selected (ionmov >= 6) and SCF mixing done on density (iscf >= 10), pawcpxocc = 2 is (by default) set to 1.

pawcross

Mnemonics: PAW - add CROSS term in oscillator strengths
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: (optdriver == 3 or optdriver == 4) and %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [0/1245] in all abinit tests, [0/159] in abinit tutorials

When pawcross=1, the overlap between the plane-wave part of one band and the on-site part of an other is taken into account in the computation of the oscillator strengths. Hence, the completeness of the on-site basis is no longer assumed.

pawecutdg

Mnemonics: PAW - Energy CUToff for the Double Grid
Characteristics: ENERGY
Mentioned in topic(s): topic_Planewaves, topic_PAW
Variable type: real
Dimensions: scalar
Default value: -1
Comment: pawecutdg MUST be specified for PAW calculations.
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Moderately used, [320/1245] in all abinit tests, [44/159] in abinit tutorials

Define the energy cut-off for the fine FFT grid (the “double grid”, that allows one to transfer data from the normal, coarse, FFT grid to the spherical grid around each atom). pawecutdg must be larger or equal to ecut. If it is equal to it, then no fine grid is used. The results are not very accurate, but the computations proceed quite fast. For typical PAW computations, where ecut is on the order of 15 Ha, pawecutdg must be tested according to what you want to do. For calculations that do not require a high accuracy (molecular dynamics for instance) a value of 20 Ha is enough. For calculations that require a high accuracy (response functions for instance) it should be on the order of 30 Ha. Choosing a larger value should not increase the accuracy, but does not slow down the computation either, only the memory. The choice made for this variable DOES have a bearing on the numerical accuracy of the results, and, as such, should be the object of a convergence study. The convergence test might be made on the total energy or derived quantities, like forces, but also on the two values of the “Compensation charge inside spheres”, a quantity written in the log file.

pawfatbnd

Mnemonics: PAW: print band structure in the FAT-BaND representation
Mentioned in topic(s): topic_PAW, topic_ElecBandStructure, topic_AtomCentered
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [6/1245] in all abinit tests, [3/159] in abinit tutorials

For Ground-State calculations using PAW and non self-consistent calculations only. This option can be used to plot band structure. For each atom (specified by natsph and iatsph), each angular momentum, and each spin polarisation, the band structure is written in files (such as e.g. FATBANDS_at0001_Ni_is2_l2_m-1). Each file contains the eigenvalue, and the contribution of angular momentum L, and projection of angular momentum M, (for the corresponding wavefunction) to the PAW density inside the PAW sphere as a function of the index of the k-point. The output can be readily plotted with the software xmgrace (e.g xmgrace FATBANDS_at0001_Ni_is2_l2_m-1). Relevant values are:

  • 0: desactivated.
  • 1: The fatbands are only resolved in L.
  • 2: The fatbands are resolved in L and M.

pawlcutd

Mnemonics: PAW - L angular momentum used to CUT the development in moments of the Densities
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 10
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

The expansion of the densities in angular momenta is performed up to l= pawlcutd . Note that, for a given system, the maximum value of pawlcutd is 2*l_max, where l_max is the maximum l of the PAW partial waves basis.

The choice made for this variable DOES have a bearing on the numerical accuracy of the results, and, as such, should be the object of a convergence study. The convergence test might be made on the total energy or derived quantities, like forces, but also on the two values of the “Compensation charge inside spheres”, a quantity written in the log file.

pawlmix

Mnemonics: PAW - maximum L used in the spherical part MIXing
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 10
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

The choice made for this variable determine how the spherical part of the density is mixed during electronic iterations.

Only parts of rhoij quantities associated with l angular momenta up to l=pawlmix are mixed. Other parts of augmentation occupancies are not included in the mixing process. This option is useful to save CPU time but DOES have a bearing on the numerical accuracy of the results.

pawmixdg

Mnemonics: PAW - MIXing is done (or not) on the (fine) Double Grid
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 0 if npfft == 1, 1 otherwise.

Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Moderately used, [15/1245] in all abinit tests, [0/159] in abinit tutorials

The choice made for this variable determines the grid on which the density (or potential) is mixed during the SCF cycle.

If pawmixdg=1 the density/potential is mixed in REAL space using the fine FFT grid (defined by pawecutdg or ngfftdg).

If pawmixdg=0 the density/potential is mixed in RECIPROCAL space using the coarse FFT grid (defined by ecut or ngfft). Only components of the coarse grid are mixed using the scheme defined by iscf; other components are only precondionned by diemix and simply mixed. This option is useful to save memory and does not affect numerical accuracy of converged results. If pawmixdg=1, density and corresponding residual are stored for previous iterations and are REAL arrays of size %nfftdg. If pawmixdg=0, density and corresponding residual are stored for previous iterations and are COMPLEX arrays of size %nfft. The memory saving is particularly efficient when using the Pulay mixing (iscf = 7 or 17).

In wavelet calculations usewvl = 1:

- pawmixdg is set to 1 by default.
- A value of 0 is not allowed.
- Density/potential is mixed in REAL space (Here only one grid is used).

pawnhatxc

Mnemonics: PAW - Flag for exact computation of gradients of NHAT density in eXchange-Correlation.
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 1
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

Relevant only when a GGA exchange-correlation functional is used. When this flag is activated, the gradients of compensation charge density (n_hat) are exactly computed (i.e. analytically); when it is deactivated, they are computed with a numerical scheme in reciprocal space (which can produce inaccurate results if the compensation charge density is highly localized). As analytical treatment of compensation charge density gradients is CPU time demanding, it is possible to bypass it with pawnhatxc = 0; but the numerical accuracy can be affected by this choice. It is recommended to test the validity of this approximation before use.

pawnphi

Mnemonics: PAW - Number of PHI angles used to discretize the sphere around each atom.
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 13
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [8/1245] in all abinit tests, [0/159] in abinit tutorials

Number of phi angles (longitude) used to discretize the data on the atomic spheres. This discretization is completely defined by pawnphi and pawntheta.

pawntheta

Mnemonics: PAW - Number of THETA angles used to discretize the sphere around each atom.
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 12
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [8/1245] in all abinit tests, [0/159] in abinit tutorials

Number of theta angles (latitude) used to discretize the data on the atomic spheres. This discretization is completely defined by pawntheta and pawnphi.

pawnzlm

Mnemonics: PAW - only compute Non-Zero LM-moments of the contributions to the density from the spheres
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 1
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

Concerns the computation of the contributions to the density from the spheres (named rho_1 - rho_tild_1). If set to 0, all lm-moments of the sphere contributions to the density are computed at each electronic iteration. If set to 1, only non-zero lm-moments of the sphere contributions to the density are computed at each electronic iteration (they are all computed at the first iteration then only those found to be non-zero will be computed; thus the first iteration is more cpu intensive)

pawoptmix

Mnemonics: PAW - OPTion for the MIXing of the spherical part
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [7/1245] in all abinit tests, [0/159] in abinit tutorials

In the case of PAW computations, during the self-consistent cycle, ABINIT mixes the density \(\rho(r)= \tilde{\rho}(r) +\hat{\rho}(r)\) and the occupancy matrix \(\rho_{ij}\). (\(\tilde{\rho}(r)\) is the pseudo density, \(\hat{\rho}(r)\) is the compensation charge density). It can be redundant as \(\rho_{ij}\) is contained in \(\hat{\rho}(r)\).

  • If pawoptmix =0: ABINIT mixes \(\rho(r)\) and \(\rho_{ij}\) but the residual used to control the mixing algorithm is only based on \(\rho(r)\).

  • If pawoptmix =1: ABINIT mixes \(\rho(r)\) and \(\rho_{ij}\) and the residual used to control the mixing algorithm is based on \(\rho(r)\) and \(\rho_{ij}\).

This has only an influence on the efficiency of the mixing algorithm. In case of mixing problems, the first suggestion is to increase the size of the history (see npulayit). Then it is also possible to play with the parameters of the Kerker mixing: diemix, diemac, etc…

pawoptosc

Mnemonics: PAW - OPTion for the computation of the OSCillator matrix elements
Mentioned in topic(s): topic_Susceptibility, topic_BSE, topic_SelfEnergy
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9

Test list (click to open). Rarely used, [4/1245] in all abinit tests, [1/159] in abinit tutorials

Only relevant for GW or Bethe-Salpeter calculations with PAW. This variable defines the approach used for the evaluation of the oscillator matrix elements within the PAW formalism. Possible values are 0,1,2. If pawoptosc = 0 the code uses its internal default value (2 for SCREENING calculations, 1 for SIGMA calculations, 2 for Bethe-Salpeter If pawoptosc = 1 the matrix elements are computed with the expression given by [Arnaud2000]. The equation is exact provided that the set of PAW partial waves is complete. If pawoptosc = 2 the matrix elements are computed with the approximated expression proposed by [Shishkin2006].

pawovlp

Mnemonics: PAW - spheres OVerLaP allowed (in percentage)
Mentioned in topic(s): topic_PAW
Variable type: real
Dimensions: scalar
Default value: 5.0
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [7/1245] in all abinit tests, [0/159] in abinit tutorials

When PAW is activated, a localized atomic basis is added to describe wave functions. Spheres around atoms are defined and they are IN PRINCIPLE not allowed to overlap. However, a small overlap can be allowed without compromising the accuracy of results. Be aware that too high overlaps can lead to unphysical results. With the pawovlp variable, the user can control the (voluminal) overlap percentage allowed without stopping the execution. pawovlp is the value (in percentage: 0…100%) obtained by dividing the volume of the overlap of two spheres by the volume of the smallest sphere. The following values are permitted for pawovlp:

  • pawovlp < 0 → overlap is always allowed
  • pawovlp = 0 → no overlap is allowed
  • pawovlp > 0 and < 100 → overlap is allowed only if it is less than pawovlp %

Note that ABINIT will not stop at the first time a too large overlap is identified, in case of ionmov/=0 or imgmov/=0, but only at the second time in the same dataset. Indeed, such trespassing might only be transient. However, a second trespassing in the same dataset, or if both ionmov=0 and imgmov=0, will induce stop.

pawprtden

Mnemonics: PAW: PRinT total physical electron DENsity
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [0/1245] in all abinit tests, [0/159] in abinit tutorials

Deprecated: See the prtden.

pawprtdos

Mnemonics: PAW: PRinT partial DOS contributions
Mentioned in topic(s): topic_PAW, topic_ElecDOS, topic_AtomCentered
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1 and prtdos == 3
Added in version: before_v9

Test list (click to open). Rarely used, [8/1245] in all abinit tests, [2/159] in abinit tutorials

This input variable controls the computation and/or printing of contributions to the PAW partial DOS in _DOS file(s):

  • Plane-waves contribution

\(+\) “on-site” all-electron contribution (\(\phi\))

\(-\) “on-site” pseudo contribution (\(\tilde{\phi}\)).

If pawprtdos=0:

  • The 3 contributions are computed; only the total partial DOS is output in _DOS file.

If pawprtdos=1:

  • The 3 contributions are computed and output in _DOS file.
  • In that case, integrated DOS is not output.

If pawprtdos=2:

  • Only “on-site” all-electron contribution is computed and output in _DOS file.
  • This a (very) good approximation of total DOS, provided that (1) the PAW local basis is complete, (2) the electronic charge is mostly contained in PAW spheres.
  • In that case, the ratsph variable is automatically set to the PAW radius.

pawprtvol

Mnemonics: PAW: PRinT VOLume
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Moderately used, [43/1245] in all abinit tests, [5/159] in abinit tutorials

Control print volume and debugging output for PAW in log file or standard output. If set to 0, the print volume is at its minimum. pawprtvol can have values from -3 to 3:

  • pawprtvol = -1 or 1: matrices \(\rho_{ij}\) (atomic occupancies) and \(D_{ij}\) (psp strength) are printed at each SCF cycle with details about their contributions.
  • pawprtvol = -2 or 2: like -1 or 1 plus additional printing: moments of “on-site” densities, details about local exact exchange.
  • pawprtvol = -3 or 3: like -2 or 2 plus additional printing: details about PAW+U, rotation matrices of spherical harmonics.

When pawprtvol >= 0, up to 12 components of \(\rho_{ij}\) and \(D_{ij}\) matrices for the 1st and last atom are printed. When pawprtvol < 0, all components of \(\rho_{ij}\) and \(D_{ij}\) matrices for all atoms are printed.

pawprtwf

Mnemonics: PAW: PRinT WaveFunctions
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

This input variable controls the output of the full PAW wave functions including the on-site contributions inside each PAW sphere needed to reconstruct the correct nodal shape in the augmentation region. pawprtwf = 1 causes the generation of a file _PAWAVES.nc containing the full wavefunctions in real space on the fine FFT grid defined by pawecutdg or ngfftdg.

Limitations: At present (v8.0), pawprtwf = 1 is not compatible with nspinor =2 and parallel executions Therefore the output of the _AE_WFK has to be done in sequential. Moreover, in order to use this feature, one has to enable the support for netcdf at configure-time as the _PAWAVES file is written using the NETCDF file format following the ETSF-IO specifications for wavefunctions in real space.

If the code is run entirely in serial, additional output is made of various contributions to the all-electron wavefunction. By default the full available set of bands and k-points are output, but a single band and k-point index can be requested by using the variables pawprt_b and pawprt_k.

pawspnorb

Mnemonics: PAW - option for SPiN-ORBit coupling
Mentioned in topic(s): topic_PAW, topic_spinpolarisation
Variable type: integer
Dimensions: scalar
Default value: 1 if nspinor == 2, 0 otherwise.

Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Moderately used, [16/1245] in all abinit tests, [1/159] in abinit tutorials

When PAW is activated, the spin-orbit coupling can be added without the use of specific PAW datasets (pseudopotentials). If pawspnorb = 1, spin-orbit will be added. If the wavefunction is spinorial (that is, if nspinor = 2), there is no reason not to include the spin-orbit interaction, so that the default value of pawspnorb becomes 1 when nspinor = 2. Note that only the all-electron “on-site” contribution to the Hamiltonian is taken into account; this is a very good approximation but requires the following conditions to be fulfilled:

1- the \(\tilde{\phi}_{i}\) basis is complete enough

2- the electronic density is mainly contained in the PAW sphere

Also note that, when spin-orbit coupling is activated and there is some magnetization nspden = 4, the time-reversal symmetry is broken. The use of kptopt = 1 or kptopt = 2 is thus forbidden. It is advised to use kptopt = 3 (no symmetry used to generate k-points) or kptopt = 4 (only spatial symmetries used to generate k-points). Be careful if you choose to use kptopt = 0 (k-points given by hand); Time- reversal symmetry has to be avoided. An artificial scaling of the spin-orbit can be introduced thanks to the spnorbscl input variable.

pawstgylm

Mnemonics: PAW - option for the STorage of G_l(r).YLM(r)
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 1
Only relevant if: %usepaw = 1
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

When PAW is activated, the computation of compensation charge density (so called “hat” density) requires the computation of \(g_{l}(r).Y_{lm}(r)\) factors (and cartesian derivatives) at each point of real space contained in PAW spheres. The number of atoms, of (l,m) quantum numbers and the sharpness of the real FFT grid can lead to a very big {\(g_{l}.Y_{lm}\)} datastructure. One can save memory by putting pawstgylm = 0; but, in that case, \(g_{l}(r).Y_{lm}(r)\) factors a re- computed each time they are needed and CPU time increases.

Possible choices:

  • pawstgylm = 0: \(g_{l}(r).Y_{lm}(r)\) are not stored in memory and recomputed.
  • pawstgylm = 1: \(g_{l}(r).Y_{lm}(r)\) are stored in memory.

Note: \(g_{l}(r)\) are shape functions (analytically known)

\(Y_{lm}(r)\) are real spherical harmonics

pawsushat

Mnemonics: PAW - SUSceptibility, inclusion of HAT (compensation charge) contribution
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1 and optdriver == 0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1245] in all abinit tests, [0/159] in abinit tutorials

Ground-State calculation only. When a sophisticated preconditioning scheme is selected for the SCF cycle of a Ground-State calculation (iprcel > 0), the computation of the susceptibility matrix is required several times during the cycle. This computation is computer time consuming, especially – within PAW – because of the inclusion of additional terms due to the compensation charge density. As only a crude valuation of the susceptibilty matrix is needed (to evaluate a preconditioning matrix), the compensation charge contribution can be neglected to save CPU time (select pawsushat = 0). This approximation could be unfavourable in some cases; in the latter, we advise to put pawsushat = 1.

Possible choices:

  • pawsushat = 0: only plane-wave contribution to suscep. matrix is computed.
  • pawsushat = 1: the whole suscep. matrix (PW + PAW on-site) is computed.

pawusecp

Mnemonics: PAW - option for the USE of CPrj in memory (cprj=WF projected with NL projector)
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 1
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

When PAW is activated, the computation of cprj arrays is memory and time consuming. When pawusecp = 0, then the cprj are never kept in memory, they are recomputed when needed (this is CPU-time consuming). When pawusecp = 1, then the cprj are computed once and then kept in memory. Change the value of the keyword only if you are an experienced user (developer). Remember:

\[ cprj = \langle\tilde{\psi}_{m}.p_{i} \rangle \]

with \(\tilde{\psi}_{n}\) is the wave function, and \(p_{i}\) the non-local projector.

For the time being, only activated for RF calculations.

pawxcdev

Mnemonics: PAW - choice for eXchange-Correlation DEVelopment (spherical part)
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: 1
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Moderately used, [21/1245] in all abinit tests, [0/159] in abinit tutorials
  • If set to 0, the exchange-correlation term in the spherical part of energy is totally computed on the angular mesh (time consuming but exact!)
  • If set to 1, the exchange-correlation term in the spherical part of energy is developed onto lm-moments at order 1
  • If set to 2, the exchange-correlation term in the spherical part of energy is developed onto lm-moments at order 2

Be careful: Response function (DFPT) + PAW + GGA requires pawxcdev = 0. But if you plan to do DFPT calculations, it is better to use this option also in the preliminary ground state calculation. However, if nspden = 4 (non-collinear calculations) with GGA and usepawu/=0, one needs to use pawxcdev = 1.

prtnabla

Mnemonics: PRint NABLA
Mentioned in topic(s): topic_printing
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [5/1245] in all abinit tests, [0/159] in abinit tutorials
  • If set to 1, calculate the matrix elements and write it in file _OPT to be read by the code conducti (see [Mazevet2010]).

ptcharge

Mnemonics: PoinT CHARGEs
Mentioned in topic(s): topic_EFG
Variable type: real
Dimensions: (ntypat)
Default value: 0
*Only relevant if: %usepaw == 1 and nucefg>=3
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

Array of point charges, in atomic units, of the nuclei. In the normal computation of electric field gradients (see nucefg) the ionic contribution is calculated from the core charges of the atomic sites. Thus for example in a PAW data set for oxygen where the core is \(1s^{2}\), the core charge is +6 (total nuclear charge minus core electron charge). In point charge models, which are much less accurate than PAW calculations, all atomic sites are treated as ions with charges determined by their valence states. In such a case oxygen almost always would have a point charge of -2. The present variable taken together with nucefg performs a full PAW computation of the electric field gradient and also a simple point charge computation. The user inputs whatever point charges he/she wishes for each atom type.

quadmom

Mnemonics: QUADrupole MOMents
Mentioned in topic(s): topic_EFG
Variable type: real
Dimensions: (ntypat)
Default value: 0
*Only relevant if: %usepaw == 1 and nucefg>1
Added in version: before_v9

Test list (click to open). Rarely used, [8/1245] in all abinit tests, [1/159] in abinit tutorials
  • Array of quadrupole moments, in barns, of the nuclei. These values are used in conjunction with the electric field gradients computed with nucefg to calculate the quadrupole couplings in MHz, as well as the asymmetries. Note that the electric field gradient at a nuclear site is independent of the nuclear quadrupole moment, thus the quadrupole moment of a nucleus can be input as 0.

spnorbscl

Mnemonics: SPin-ORBit SCaLing
Mentioned in topic(s): topic_PAW, topic_spinpolarisation
Variable type: real
Dimensions: scalar
Default value: 1.0
Only relevant if: ( %usepaw == 1 and pawspnorb >= 1) .or NC pseudos with SOC terms.
Added in version: before_v9

Test list (click to open). Rarely used, [6/1245] in all abinit tests, [0/159] in abinit tutorials

Scaling of the spin-orbit interaction. The default values (one) gives the first-principles value, while other values are used for the analysis of the effect of the spin-orbit interaction, but are not expected to correspond to any physical situation.

Note that, starting with version 9.5.2, this option is also compatible with NC pseudos provided the pseudopotential files include the SOC term.

upawu

Mnemonics: value of U for PAW+U
Characteristics: ENERGY
Mentioned in topic(s): topic_DFT+U
Variable type: real
Dimensions: (ntypat)
Default value: 0
*Only relevant if: %usepaw == 1 and usepawu == 1
Added in version: before_v9

Test list (click to open). Moderately used, [56/1245] in all abinit tests, [7/159] in abinit tutorials

Gives the value of the screened coulomb interaction between correlated electrons corresponding to lpawu for each species. In the case where lpawu =-1, the value is not used. In the case of a GW calculation, the U interaction defined by upawu will be REMOVED from the self energy. In particular, for G0 W0 calculations (perturbative calculations), the energy eigenvalues obtained after an underlying DFT+U calculation will be

\[E_{GW} = E_{DFT+U} + < \phi | Self-energy - U | \phi>\]

Actually, in order to perform a GW @ DFT+U calculation, one should define the same value of U in the self-energy calculation, than the one defined in the DFT calculation. The easiest is actually to define the value of U for the whole set of calculations (for the different datasets), including the screening, even if the U value does not play explicitly a role in the computation of the latter (well, the input wavefunctions will be different anyhow). It is possible to perform calculations of the type GW+\(U^{'}\) @ DFT+U, so keeping a \(U^{'}\) interaction (usually smaller than the initial U) in the GW calculation. This value will be subtracted in the GW correction calculation, as outlined above. Explicitly, in order to do a calculation of a material with a DFT U value of 7.5 eV, followed by a GW calculation where there is a residual U value of 2 eV, one has to define:

  upawu1   7.5 eV   ! This is for the DFT calculation
...
optdriver4  4
upawu4   5.5 eV   ! This is for the screening calculation

usedmatpu

Mnemonics: USE of an initial Density MATrix in Paw+U
Mentioned in topic(s): topic_DFT+U
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1 and usepawu == 1
Added in version: before_v9

Test list (click to open). Moderately used, [16/1245] in all abinit tests, [2/159] in abinit tutorials

When usedmatpu /=0, an initial density matrix (given by dmatpawu keyword) is used and kept fixed during the first ABS( usedmatpu ) SCF steps. This starting value of the density matrix can be useful to find the correct ground state. Within DFT+U formalism, finding the minimal energy of the system is tricky; thus it is advised to test several values of the initial density matrix. Note also that the density matrix has to respect some symmetry rules determined by the space group. If the symmetry is not respected in the input, the matrix is however automatically symmetrised.

The sign of usedmatpu has influence only when ionmov /= 0 (dynamics or relaxation):

  • When usedmatpu >0, the density matrix is kept constant only at first ionic step
  • When usedmatpu <0, the density matrix is kept constant at each ionic step

useexexch

Mnemonics: USE of EXact EXCHange
Mentioned in topic(s): topic_xc
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Rarely used, [1/1245] in all abinit tests, [0/159] in abinit tutorials

When useexexch = 1, the hybrid functional PBE0 is used in PAW, inside PAW spheres only, and only for correlated orbitals given by lexexch. To change the ratio of exact exchange, see also exchmix.

usepawu

Mnemonics: USE PAW+U (spherical part)
Mentioned in topic(s): topic_DFT+U, topic_PAW, topic_GW, topic_SelfEnergy
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Moderately used, [62/1245] in all abinit tests, [7/159] in abinit tutorials

Must be non-zero if a DFT+U calculation is done, or if a GW calculation following a DFT+U calculation is done (important!), or if a DMFT calculation is done..

  • If set to 0, the DFT+U method is not used.

  • If the absolute value is set to 1, 2 or 4, the DFT+U method (cf [Anisimov1991a]) is used. The full rotationally invariant formulation is used (see Eq. (3) of [Liechtenstein1995]) for the interaction term of the energy. Three choices are allowed concerning the double counting term:

    • If abs( usepawu ) = 1 or 10, the Full Localized Limit (FLL) (or Atomic limit) double counting is used (cf Eq. (4) of [Liechtenstein1995] or Eq. (8) of [Czyzyk1994]).

    • If abs( usepawu ) = 2, the Around Mean Field (AMF) double counting is used (cf Eq. (7) of [Czyzyk1994]). Not valid if nspinor=2.

    • If abs( usepawu ) = 4 or 14, the FLL double counting is used. However, and in comparison to usepaw=1, the calculation is done without polarization in the exchange correlation functional (cf [Park2015] and [Chen2016a]). In this case, one must use iscf<10.

For DMFT calculations usedmft=1, only usepawu =10 or 14 is permitted. For other types of calculations, abs( usepawu )=10 or 14 cannot be used. Positive and negative values of usedmft, only differ by their internal implementation. At some stage, only positive values will be used again.

If nspden = 4 (non-collinear calculations) with GGA, one needs to use pawxcdev = 1, and either abs( usepawu )=0, 1, 4, 10 or 14.

If DFT+U is activated ( usepawu /=0), the lpawu, upawu and jpawu input variables are read. The implementation is done inside PAW augmentation regions only (cf [Bengone2000]). The initial density matrix can be given in the input file (see usedmatpu). The expression of the density matrix is chosen thanks to dmatpuopt. In the case of a GW calculation on top of a DFT+U, the absence of definition of a U value in the self-energy will LEAVE the underlying U from the DFT calculation. Thus, the code will actually do a GW+U @ DFT+U calculation. Note that the screening calculation will not be affected by the presence/absence of a U value. Actually, in order to perform a GW @ DFT+U calculation, one should define the same value of U in the self-energy calculation, than the one defined in the DFT calculation. The code will know that the interaction corresponding to that value has to be SUBTRACTED inside the self-energy. The easiest is actually to define the presence of U for the whole set of calculations (for the different datasets), including the screening, even if the U value does not play explicitly a role in the computation of the latter (well, the input wavefunctions will be different anyhow). It is possible to perform calculations of the type GW+\(U^{'}\) @ DFT+U, so keeping a smaller U interaction in the GW calculation, by subtracting a smaller U than the one used in the DFT calculation. See the description of the upawu input variable.

Suggested acknowledgment [Amadon2008a].

usexcnhat

Mnemonics: USE eXchange-Correlation with NHAT (compensation charge density)
Mentioned in topic(s): topic_PAW
Variable type: integer
Dimensions: scalar
Default value: -1
Only relevant if: %usepaw == 1
Added in version: before_v9

Test list (click to open). Moderately used, [26/1245] in all abinit tests, [1/159] in abinit tutorials

This flag determines how the exchange-correlation terms are computed for the pseudo-density.

  • When usexcnhat = 0, the exchange-correlation potential does not include the compensation charge density, i.e. \(V_{xc}=V_{xc}(\tilde{n}_{core} + \tilde{n}_{valence})\).

  • When usexcnhat = 1, the exchange-correlation potential includes the compensation charge density, i.e. \(V_{xc}=V_{xc}(\tilde{n}_{core} + \tilde{n}_{valence}+\hat{n})\).

  • When usexcnhat = -1,the value of usexcnhat is determined from the reading of the PAW dataset file (pseudopotential file).

When PAW datasets with different treatment of \(V_{xc}\) are used in the same run, the code stops.

The difference between these treatments has been studied in detail in [Torrent2010]. The choice usexcnhat = 1 is implemented in VASP and QE, but usexcnhat = 0 is not available in these software (as of 2022). However, in [Torrent2010] several advantages of the choice usexcnhat = 0 are made clear.

The value usexcnhat = 0 corresponds to Bloechl form, see Eq.(2) of [Torrent2010]. The PAW atomic datasets from JTH table [Jollet2014] yield usexcnhat = 0 by default, and it is expected that all future versions of this table will also yield usexcnhat = 0 by default.. The value usexcnhat = 1 corresponds to Kresse form, see Eq.(3) of [Torrent2010]. With ABINIT, only the oldest PAW atomic datasets favour usexcnhat = 1.

Still, the ABINIT user has both options.