dfpt input variables¶
This document lists and provides the description of the name (keywords) of the dfpt input variables to be used in the input file for the abinit executable.
bdeigrf¶
Mnemonics: BanD for secondorder EIGenvalues from ResponseFunction
Mentioned in topic(s): topic_TDepES
Variable type: integer
Dimensions: scalar
Default value: 1
Only relevant if: ieig2rf in [1,2,3,4,5]
Added in version: before_v9
Test list (click to open). Moderately used, [15/1027] in all abinit tests, [0/121] in abinit tutorials
The variable bdeigrf is the maximum number of bands for which the second order eigenvalues must be calculated: the full number of bands is still used during the computation of these corrections.
If bdeigrf is set to 1, the code will automatically set bdeigrf equal to nband.
d3e_pert1_atpol¶
Mnemonics: 3^{rd} Derivative of Energy, mixed PERTurbation 1: limits of ATomic POLarisations
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: (2)
Default value: [1, 1]
Only relevant if: optdriver == 5 (nonlinear response computations)
Added in version: before_v9
Test list (click to open). Moderately used, [27/1027] in all abinit tests, [6/121] in abinit tutorials
Controls the range of atoms for which displacements will be considered in nonlinear computations (using the 2n+1 theorem), for the 1^{st} perturbation. May take values from 1 to natom, with d3e_pert1_atpol (1)<= d3e_pert1_atpol (2). See rfatpol for additional details.
d3e_pert1_dir¶
Mnemonics: 3^{rd} Derivative of Energy, mixed PERTurbation 1: DIRections
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: (3)
Default value: [0, 0, 0]
Only relevant if: optdriver == 5 (nonlinear response computations)
Added in version: before_v9
Test list (click to open). Moderately used, [27/1027] in all abinit tests, [6/121] in abinit tutorials
Gives the directions to be considered in nonlinear computations (using the 2n+1 theorem), for the 1^{st} perturbation. The three elements corresponds to the three primitive vectors, either in real space (atomic displacement), or in reciprocal space (electric field perturbation). See rfdir for additional details.
d3e_pert1_elfd¶
Mnemonics: 3^{rd} Derivative of Energy, mixed PERTurbation 1: ELectric FielD
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: optdriver == 5 (nonlinear response computations)
Added in version: before_v9
Test list (click to open). Moderately used, [27/1027] in all abinit tests, [6/121] in abinit tutorials
Turns on electric field perturbation in nonlinear computation, as 1^{st} perturbation. Actually, such calculations requires first the nonself consistent calculation of derivatives with respect to k, independently of the electric field perturbation itself. See rfelfd for additional details.
d3e_pert1_phon¶
Mnemonics: 3^{rd} Derivative of Energy, mixed PERTurbation 1: PHONons
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: optdriver == 5 (nonlinear response computations)
Added in version: before_v9
Test list (click to open). Moderately used, [27/1027] in all abinit tests, [6/121] in abinit tutorials
Turns on atomic displacement perturbation in nonlinear computation, as 1^{st} perturbation. See rfphon for additional details.
d3e_pert2_atpol¶
Mnemonics: 3^{rd} Derivative of Energy, mixed PERTurbation 2: limits of ATomic POLarisations
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: (2)
Default value: [1, 1]
Only relevant if: optdriver == 5 (nonlinear response computations)
Added in version: before_v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [0/121] in abinit tutorials
 v3: t83.in
Controls the range of atoms for which displacements will be considered in non linear computations (using the 2n+1 theorem), for the 2^{nd} perturbation. May take values from 1 to natom, with d3e_pert2_atpol (1) <= d3e_pert2_atpol (2). See rfatpol for additional details.
d3e_pert2_dir¶
Mnemonics: 3^{rd} Derivative of Energy, mixed PERTurbation 2: DIRections
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: (3)
Default value: [0, 0, 0]
Only relevant if: optdriver == 5 (nonlinear response computations)
Added in version: before_v9
Test list (click to open). Moderately used, [27/1027] in all abinit tests, [6/121] in abinit tutorials
Gives the directions to be considered in nonlinear computations (using the 2n+1 theorem), for the 2^{nd} perturbation. The three elements corresponds to the three primitive vectors, either in real space (atomic displacement), or in reciprocal space (electric field perturbation). See rfdir for additional details.
d3e_pert2_elfd¶
Mnemonics: 3^{rd} Derivative of Energy, mixed PERTurbation 2: ELectric FielD
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: optdriver == 5 (nonlinear response computations)
Added in version: before_v9
Test list (click to open). Moderately used, [27/1027] in all abinit tests, [6/121] in abinit tutorials
Turns on electric field perturbation in nonlinear computation, as 2^{nd} perturbation. Actually, such calculations requires first the nonself consistent calculation of derivatives with respect to k, independently of the electric field perturbation itself. See rfelfd for additional details.
d3e_pert2_phon¶
Mnemonics: 3^{rd} Derivative of Energy, mixed PERTurbation 2: PHONons
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: optdriver == 5 (nonlinear response computations)
Added in version: before_v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [0/121] in abinit tutorials
 v3: t83.in
Turns on atomic displacement perturbation in nonlinear computation, as 2^{nd} perturbation. See rfphon for additional details.
d3e_pert3_atpol¶
Mnemonics: 3^{rd} Derivative of Energy, mixed PERTurbation 3: limits of ATomic POLarisations
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: (2)
Default value: [1, 1]
Only relevant if: optdriver == 5 (nonlinear response computations)
Added in version: before_v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [0/121] in abinit tutorials
 v3: t83.in
Controls the range of atoms for which displacements will be considered in non linear computations (using the 2n+1 theorem), for the 3^{rd} perturbation. May take values from 1 to natom, with d3e_pert3_atpol (1)<= d3e_pert3_atpol (2). See rfatpol for additional details.
d3e_pert3_dir¶
Mnemonics: 3^{rd} Derivative of Energy, mixed PERTurbation 3: DIRections
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: (3)
Default value: [0, 0, 0]
Only relevant if: optdriver == 5 (nonlinear response computations)
Added in version: before_v9
Test list (click to open). Moderately used, [27/1027] in all abinit tests, [6/121] in abinit tutorials
Gives the directions to be considered in nonlinear computations (using the 2n+1 theorem), for the 3^{rd} perturbation. The three elements corresponds to the three primitive vectors, either in real space (atomic displacement), or in reciprocal space (electric field perturbation). See rfdir for additional details.
d3e_pert3_elfd¶
Mnemonics: 3^{rd} Derivative of Energy, mixed PERTurbation 3: ELectric FielD
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: optdriver == 5 (nonlinear response computations)
Added in version: before_v9
Test list (click to open). Moderately used, [27/1027] in all abinit tests, [6/121] in abinit tutorials
Turns on electric field perturbation in nonlinear computation, as 3^{rd} perturbation. Actually, such calculations requires first the nonself consistent calculation of derivatives with respect to k, independently of the electric field perturbation itself. See rfelfd for additional details.
d3e_pert3_phon¶
Mnemonics: 3^{rd} Derivative of Energy, mixed PERTurbation 3: PHONons
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: optdriver == 5 (nonlinear response computations)
Added in version: before_v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [0/121] in abinit tutorials
 v3: t83.in
Turns on atomic displacement perturbation in nonlinear computation, as 3^{rd} perturbation. See rfphon for additional details.
dfpt_sciss¶
Mnemonics: DFPT SCISSor operator
Characteristics: ENERGY
Mentioned in topic(s): topic_DFPT
Variable type: real
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [0/121] in abinit tutorials
 v7: t46.in
It is the value of the “scissors operator”, the shift of conduction band eigenvalues, used in response function calculations. Can be specified in Ha (the default), Ry, eV or Kelvin, since ecut has the ENERGY characteristics (1 Ha = 27.2113845 eV). Typical use is for response to electric field (rfelfd = 3), but NOT for d/dk (rfelfd = 2) and phonon responses.
efmas¶
Mnemonics: EFfective MASs
Mentioned in topic(s): topic_EffectiveMass
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Rarely used, [6/1027] in all abinit tests, [0/121] in abinit tutorials
Turns on effective mass tensor calculations. Such calculations requires the nonselfconsistent calculation of derivatives with respect to k, in the same dataset. It must therefore be used with rfelfd = 2 (or 1).
 0 → no effective mass tensor calculation
 1 → effective mass tensor calculation
Note
At the present time, both normconserving (NC) and PAW calculations are supported. Also, for PAW calculations only, nspinor == 2 and pawspnorb == 1 (i.e. spinorbit (SO) calculations) is supported. NC SO calculations are NOT currently supported. Also, for both NC and PAW, nspden/=1 and nsppol/=1 are NOT supported.
efmas_bands¶
Mnemonics: EFfective MASs, BANDS to be treated.
Mentioned in topic(s): topic_EffectiveMass
Variable type: integer
Dimensions: (2,nkpt)
Default value: The full range of band available in the calculation for each kpoint.
Only relevant if: efmas == 1
Added in version: before_v9
Test list (click to open). Rarely used, [6/1027] in all abinit tests, [0/121] in abinit tutorials
This variable controls the range of bands for which the effective mass is to be calculated. If a band is degenerate, all other bands of the degenerate group will automatically be treated, even if they were not part of the user specified range.
efmas_calc_dirs¶
Mnemonics: EFfective MASs, CALCulate along DIRectionS
Mentioned in topic(s): topic_EffectiveMass
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: efmas == 1
Added in version: before_v9
Test list (click to open). Rarely used, [5/1027] in all abinit tests, [0/121] in abinit tutorials
Allows the user to calculate the scalar effective mass of all bands specified by efmas_bands along specific directions in reciprocal space. This is particularly useful when considering degenerate bands, which are usually warped, and thus cannot have their dispersion (hessian) and effective mass expressed as a tensor. This allows the user to see the more complex angular behavior of effective masses in these cases, for instance.
When efmas_calc_dirs == 0, no directions are read from the input file (using efmas_dirs) and the effective masses along the 3 cartesian directions are output by default.
When efmas_calc_dirs == 1, 2 or 3, efmas_n_dirs directions are read from efmas_dirs, assuming cartesian, reduced or angular (\theta,\phi) coordinates, respectively. In the case efmas_calc_dirs == 3, 2 real values per directions are read, whereas 3 real values are read in the two other cases.
efmas_deg¶
Mnemonics: EFfective MASs, activate DEGenerate formalism
Mentioned in topic(s): topic_EffectiveMass
Variable type: integer
Dimensions: scalar
Default value: 1
Only relevant if: efmas > 0
Added in version: before_v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [0/121] in abinit tutorials
 v7: t82.in
Activate (==1) or not (==0) the treatment of degenerate bands (criterion efmas_deg_tol is used to determine whether bands are degenerate). Also compute the transport equivalent effective mass (see [Mecholsky2014]).
efmas = 0 should only be used for testing purposes.
efmas_deg_tol¶
Mnemonics: EFfective MASs, DEGeneracy TOLerance
Mentioned in topic(s): topic_EffectiveMass
Variable type: real
Dimensions: scalar
Default value: 1e05
Only relevant if: efmas_deg == 1
Added in version: before_v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [0/121] in abinit tutorials
 v7: t82.in
Energy difference below which 2 bands are considered degenerate (and treated using the formalism activated with efmas_deg == 1). efmas_deg_tol has the ENERGY characteristics.
efmas_dim¶
Mnemonics: EFfective MASs, DIMension of the effective mass tensor
Mentioned in topic(s): topic_EffectiveMass
Variable type: integer
Dimensions: scalar
Default value: 3
Only relevant if: efmas == 1
Added in version: before_v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [0/121] in abinit tutorials
 v7: t80.in
For 2D or 1D systems, the band dispersion goes to 0 perpendicular to the system, which causes the inverse effective mass to be singular, i.e. the effective mass to be NaN. This keyword circumvents the problem by eliminating the troublesome dimensions from the inverse effective mass.
In 2D, the Z axis is ignored and, in 1D, the Z and Y axis are ignored.
Also, note that in the 2D degenerate case, a subtlety arises: the ‘transport equivalent’ effective mass does not determine the scale of the transport tensors (conductivity and others). Therefore, for this specific case, the factor by which these transport tensors should be scaled once determined from the ‘transport equivalent’ effective mass tensor is output separately on the line immediately after the effective mass.
efmas_dirs¶
Mnemonics: EFfective MASs, DIRectionS to be calculated
Mentioned in topic(s): topic_EffectiveMass
Variable type: real
Dimensions: (3 or 2,efmas_n_dirs)
Default value: 0
Only relevant if: efmas_calc_dirs > 0
Added in version: before_v9
Test list (click to open). Rarely used, [5/1027] in all abinit tests, [0/121] in abinit tutorials
List of efmas_n_dirs directions to be considered according to the value of efmas_calc_dirs. The directions are specified by 3 real values if efmas_calc_dirs == 1 or 2 and by 2 real values if efmas_calc_dirs == 3.
efmas_n_dirs¶
Mnemonics: EFfective MASs, Number of DIRectionS
Mentioned in topic(s): topic_EffectiveMass
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: efmas_calc_dirs > 0
Added in version: before_v9
Test list (click to open). Rarely used, [5/1027] in all abinit tests, [0/121] in abinit tutorials
Number of directions in efmas_dirs, to be considered according to efmas_calc_dirs.
efmas_ntheta¶
Mnemonics: EFfective MASs, Number of points for integration w/r to THETA
Mentioned in topic(s): topic_EffectiveMass
Variable type: integer
Dimensions: scalar
Default value: 1000
Only relevant if: efmas == 1 and efmas_bands == (degenerate band index)
Added in version: before_v9
Test list (click to open). Rarely used, [6/1027] in all abinit tests, [0/121] in abinit tutorials
When a band is degenerate, the usual definition of effective mass becomes invalid. However, it is still possible to define a ‘transport equivalent mass tensor’ that reproduces the contribution of the band to the conductivity tensor. To obtain this tensor, an integration over the solid sphere is required. The angular variables are sampled using efmas_ntheta points for the theta coordinate, and twice efmas_ntheta points for the phi coordinate. The default value gives a tensor accurate to the 4^{th} decimal in Ge.
elph2_imagden¶
Mnemonics: ELectronPHonon interaction at 2^{nd} order: IMAGinary shift of the DENominator
Characteristics: ENERGY
Mentioned in topic(s): topic_TDepES
Variable type: real
Dimensions: scalar
Default value: 0.0
Only relevant if: ieig2rf != 0
Added in version: before_v9
Test list (click to open). Moderately used, [19/1027] in all abinit tests, [4/121] in abinit tutorials
 paral: t59.in, t59.in, t59.in, t59.in, t60.in, t60.in, t60.in
 tutorespfn: tdepes_1.in, tdepes_2.in, tdepes_3.in, tdepes_4.in
 v6: t37.in
 v7: t50.in, t51.in, t55.in, t57.in, t58.in, t59.in, t83.in
The variable elph2_imagden determines the imaginary shift of the denominator of the sumoverstates in the perturbation, (e_{nk}e_{n'k'}+i elph2_imagden ). One should use a width comparable with the Debye frequency or the maximum phonon frequency. Can be specified in Ha (the default), Ry, eV or Kelvin, since ecut has the ENERGY characteristics (1 Ha = 27.2113845 eV).
esmear¶
Mnemonics: Eigenvalue SMEARing
Characteristics: ENERGY
Mentioned in topic(s): topic_TDepES
Variable type: real
Dimensions: scalar
Default value: 0.01
Only relevant if: smdelta != 0
Added in version: before_v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [0/121] in abinit tutorials
 v6: t60.in
The variable esmear determines the width of the functions approximating the delta function, \delta(e_{nk}e_{n'k'}), present in the expression of the lifetimes. One should use a width comparable with the Debye frequency or the maximum phonon frequency. Can be specified in Ha (the default), Ry, eV or Kelvin, since ecut has the ENERGY characteristics (1 Ha = 27.2113845 eV).
frzfermi¶
Mnemonics: FReeZe FERMI energy
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Rarely used, [3/1027] in all abinit tests, [0/121] in abinit tutorials
Can be used to suppress artificially the firstorder change of Fermi energy, in case of Response Function calculation for metals at Q=0. If the input variable frzfermi is set to 1, this contribution is suppressed, even though this is incorrect.
ieig2rf¶
Mnemonics: Integer for secondorder EIGenvalues from ResponseFunction
Mentioned in topic(s): topic_TDepES
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Moderately used, [26/1027] in all abinit tests, [4/121] in abinit tutorials
 paral: t59.in, t59.in, t59.in …
 tutorespfn: tdepes_1.in, tdepes_2.in, tdepes_3.in …
 v5: t26.in …
 v6: t37.in, t50.in, t54.in …
 v7: t50.in, t51.in, t55.in …
If ieig2rf is greater than 0, the code will produce a file, named with the suffix _EIGR2D, containing the secondorder electronic eigenvalues for the perturbation. These files are used in the calculation of the thermal correction to the electronic eigenvalues.

If ieig2rf is set to 1, the secondorder electronic eigenvalues will be calculated from the DFPT method (Sternheimer).

If ieig2rf is set to 2, the secondorder electronic eigenvalues will be calculated from the AllenCardona method (sum over states).

If ieig2rf is set to 3, the secondorder electronic eigenvalues will be calculated from the DFPT method (sum over states) but using a different part of the code. This is equivalent to ieig2rf = 1 [debuging].

If ieig2rf is set to 4, the secondorder electronic eigenvalues will be calculated from the dynamical DFPT method (Sternheimer). The code will generate _EIGR2D.nc files that contain the electronphonon matrix element squared on the space orthogonal to the active space. The code will also produce _FAN.nc files that contain the electronphonon matrix elements squared.

If ieig2rf is set to 5, the secondorder electronic eigenvalues will be calculated from the dynamical DFPT method (Sternheimer). The code will generate _EIGR2D.nc files that contain the electronphonon matrix element square on the space orthogonal to the active space. The code will also produce _GKK.nc files that contain electronphonon matrix elements. This option is preferable for large system to ieig2rf = 4 as the GKK files take much less disk space and memory (but run a little bit slower).
Note
ieig2rf = 4 and 5 can only be used if Abinit is compiled with NETCDF support.
Related variables: bdeigrf, elph2_imagden, getgam_eig2nkq, smdelta
ixcrot¶
Mnemonics: Index of the XC ROTation method used to calculate firstorder exchangecorrelation potential in noncollinear DFPT calculations
Mentioned in topic(s): topic_DFPT, topic_xc
Variable type: integer
Dimensions: scalar
Default value: 1
Added in version: before_v9
Test list (click to open). Moderately used, [12/1027] in all abinit tests, [0/121] in abinit tutorials
Method of calculation of the 1^{st} order XC potential in noncollinear DFPT calculations. The possible values 1,2 and 3 correspond to the following methods:
 If ixcrot=1, the spinor rotation matrix U at each FFT point is not calculated explicitly. Instead the needed expressions involving U are derived based on the general properties of the U matrix.
 If ixcrot=2, U is computed explicitly
 If ixcrot=3, the brute force evaluation of the 1^{st} order XC potential as a functional derivative is used. Rotation matrices are not computed.
In theory, all methods give identical results. However, due to different implementation approaches, the roundoff errors can lead to slight differences intermediate and final results obtained using methods 1,2 and 3. The choice of the method can also affect the convergence. For more details, see [Ricci2019] or [Gonze2020]. WARNING: in [Ricci2019], the meaning of ixcrot =2 or 3 is inverted with respect to the implementation. On the contrary, the implemention and [Gonze2020] agree. More explicitly, the method refered to as method 1’ in [Ricci2019] is ixcrot =2, and method refereed to as method 2 in [Ricci2019] is ixcrot =3.
Note
For nonzero perturbation wavevector (qpt/=0), only the ixcrot =3 implementation is currently available. The code will stop with the default ixcrot value for nonzero perturbation wavevector. The user should then set ixcrot =3 and restart.
lw_flexo¶
Mnemonics: LongWave calculation of FLEXOelectricity related spatial dispersion tensors
Characteristics: DEVELOP
Mentioned in topic(s): topic_longwave
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: optdriver = 10
Added in version: v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [1/121] in abinit tutorials
 tutorespfn: tlw_1.in
Used to run the calculation of spatial dispersion tensorial quantities needed to build the bulk flexoelectric tensor (the clampedion contribution is alread calculated by abint whereas the mixed and latticemediated ones are obtained through a postprocessing anaddb calculation, see flexoflag@anaddb).
At present (May 18, 2020 ), all the elements of the spatial dispersion tensors are necessarily calculated. This requires the precalculation of the groundstate wavefunctions and density as well as response functions and densities to a set of perturbations as specified below. All perturbations and directions need to be explicictly computed, and the linear response calculations have to be performed with prepalw = 1.
 0 → No flexoelectric spatial dispersion tensors are calculated.
 1 → Four tensors required to build all the contributions to the bulk flexoelectric tensor are calculated. Requires precomputed linear response functions and densities: ddk, d2_dkdk, electric field, atomic displacement and strain.
 2 → Clampedion flexoelectric tensor is calculated. Requires precomputed linear response functions and densities: ddk, d2_dkdk, electric field and strain.
 3 → Two tensors required to build the mixed flexoelectric tensor are calculated: the first moment of polarization response to an atomic displacement and the first moment of the IFCs. Related quantities that can be derived from these two tensors are also printed: dynamical quadrupoles, clampedion piezoelectric tensor and piezoelectric force response tensor. Requires precomputed linear response functions and densities: ddk, d2_dkdk, electric field and atomic displacement.
 4 → Two tensors required to build the latticemediated flexoelectric tensor are calculated: the first moment of the IFCs and the first moment of the piezoelectric force response tensor. Related quantities that can be derived from these two tensors are also printed: piezoelectric force response tensor and clampedion elastic tensor. Requires precomputed linear response functions and densities: ddk, atomic displacement and strain.
lw_qdrpl¶
Mnemonics: LongWave calculation of dynamical QuaDRuPoLes tensor
Characteristics: DEVELOP
Mentioned in topic(s): topic_longwave
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: optdriver = 10
Added in version: v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [1/121] in abinit tutorials
 tutorespfn: tlw_4.in
Used to run dynamical quadrupoles tensor calculation (e.g., needed to include dipolequadrupole and/or quadrupolequadrupole electrostatic interactions in the anaddb calculation of phonons. See dipquad@anaddb and quadquad@anaddb).
 0 → No dynamical quadrupoles are calculated
 1 → Dynamical quadrupoles are calculated. Related quantities that can be derived from the dynamical quadrupoles are also printed: the first moment of the polarization response to an atomic displacement and the clampedion piezoelectric tensor.
At present (May 18, 2020 ), all the elements of the dynamical quadrupoles tensor are necessarily calculated. This requires the precalculation of the groundstate wave functions and density as well as response functions and densities to the following perturbations: ddk, d2_dkdk, atomic displacements and electric fields. All perturbations and directions need to be explicictly computed, and the linear response calculations have to be performed with prepalw = 1.
nonlinear_info¶
Mnemonics: Output NONLINEAR INFOrmation
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: optdriver == 5 and usepead == 0, or rf2_dkdk/=0 or rf2_dkde/=0
Added in version: before_v9
Test list (click to open). Rarely used, [9/1027] in all abinit tests, [0/121] in abinit tutorials
Control the output of the nonlinear implementation (only when usepead == 0). The default value, nonlinear_info == 0 does nothing. If nonlinear_info == 1, different contributions of 3^{rd} derivatives of the energy are written in the output file (non time consuming).
Higher values activate some internal tests for checking the implementation correctness (time consuming, not useable in parallel). If nonlinear_info == 2, same effect than 1 and tests are done in nonlinear (optdriver==5 and usepead == 0). If nonlinear_info == 3, same effect than 1 and tests are done in rf2_init (rf2_dkdk/=0 or rf2_dkde/=0). If nonlinear_info == 4, same effect than 1 and tests are done in both nonlinear and rf2_init. A line containining “NOT PASSED” (and other information) is added to the output file for each test that does not pass, otherwise nothing is printed. However, more information concerning the tests is always printed in the standard output file.
prepalw¶
Mnemonics: PREPAre LongWave calculation
Characteristics: DEVELOP
Mentioned in topic(s): topic_longwave
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: v9
Test list (click to open). Rarely used, [2/1027] in all abinit tests, [2/121] in abinit tutorials
The computation of spatial dispersion quantities from the longwave DFPT approach requires the firstorder wavefunctions and densities obtained from a linear response calculation. The standard approach in a linear response calculation is:
 compute only the irreducible perturbations;
 use symmetries to reduce the number of kpoints for the kpoint integration.
This approach cannot be applied, presently (v9.0), if the firstorder wavefunctions are to be used to compute spatial dispersion properties. During the linear response calculation, in order to prepare a longwave calculation, one should put prepalw to 1 in order to force ABINIT to compute all the perturbations explicitly, and to keep the full number of kpoints in half the BZ (kptopt=2), or the full BZ (kptopt=3).
prepanl¶
Mnemonics: PREPAre NonLinear response calculation
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Moderately used, [26/1027] in all abinit tests, [6/121] in abinit tutorials
The computation of thirdorder derivatives from the 2n+1 theorem requires the firstorder wavefunctions and densities obtained from a linear response calculation. The standard approach in a linear response calculation is:
 compute only the irreducible perturbations;
 use symmetries to reduce the number of kpoints for the kpoint integration.
This approach cannot be applied, presently (v4.1), if the firstorder wavefunctions are to be used to compute thirdorder derivatives. First, for electric fields, the code needs the derivatives along the three directions. Still, in case of phonons, only the irreducible perturbations are required. Second, for both electric fields and phonons, the wavefunctions must be available in half the BZ (kptopt=2), or the full BZ (kptopt=3). During the linear response calculation, in order to prepare a nonlinear calculation, one should put prepanl to 1 in order to force ABINIT to compute the electric field perturbation along the three directions explicitly, and to keep the full number of kpoints.
In the case of a 2^{nd} derivative of wavefunction (rf2_dkdk or rf2_dkde), prepanl == 1 can be used in order to skip directions of perturbations that will not be used by the nonlinear routine (see rf2_dkdk for more details).
prepgkk¶
Mnemonics: PREPAre GKK calculation
Mentioned in topic(s): topic_ElPhonInt
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Rarely used, [5/1027] in all abinit tests, [1/121] in abinit tutorials
The calculation of electronphonon coupling quantities requires the presence of all the perturbations (all atoms in all directions) for the chosen set of (irreducible) qpoints. To impose this and prevent ABINIT from using symmetry to reduce the number of perturbations, set prepgkk to 1. Use in conjunction with prtgkk.
prtbbb¶
Mnemonics: PRinT BandByBand decomposition
Mentioned in topic(s): topic_printing, topic_Output
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [0/121] in abinit tutorials
 v3: t77.in
If prtbbb is 1, print the bandbyband decomposition of Born effective charges and localization tensor, in case they are computed. See [Ghosez2000].
prtefmas¶
Mnemonics: PRint EFfective MASs data
Mentioned in topic(s): topic_printing, topic_EffectiveMass
Variable type: integer
Dimensions: scalar
Default value: 1
Only relevant if: efmas == 1
Added in version: before_v9
Test list (click to open). Rarely used, [2/1027] in all abinit tests, [0/121] in abinit tutorials
If 1, at the end of an effective mass calculation (efmas = 1), create a file *_EFMAS, that contains the generalized secondorder kderivatives, see Eq.(66) in [Laflamme2016], in view of further processing.
prtfull1wf¶
Mnemonics: PRinT FULL 1^{st}order WaveFunction
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [0/121] in abinit tutorials
 v8: t36.in
If set to 1, the output _1WF files will contain the full 1^{st}order wavefunctions, for both valence and conduction bands. Otherwise, the _1WF files are not really 1^{st}order perturbed wavefunctions, but merely a set of perturbed wavefunctions that yield the correct perturbed density. This is used when one expect to perform postprocessing of the 1^{st}order wavefunctions.
rf2_dkde¶
Mnemonics: Response Function: mixed 2^{nd} Derivative of wavefunctions with respect to K and electric field
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Rarely used, [9/1027] in all abinit tests, [0/121] in abinit tutorials
If is equal to 1, activates computation of mixed second derivatives of wavefunctions with respect to wavevector and electric field (ipert = natom+11 is activated). This is not strictly a response function but is a needed auxiliary quantity in the calculations of 3^{rd}order derivatives of the energy (nonlinear response) if usepead == 0. The directions for the derivatives are determined by rf2_pert1_dir, rf2_pert2_dir and prepanl in the same way than rf2_dkdk.
rf2_dkdk¶
Mnemonics: Response Function: 2^{nd} Derivative of wavefunctions with respect to K
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Moderately used, [11/1027] in all abinit tests, [2/121] in abinit tutorials
If is equal to 1, activates computation of second derivatives of wavefunctions with respect to wavevectors (ipert = natom+10 is activated). This is not strictly a response function but is a needed auxiliary quantity in the calculations of 3^{rd}order derivatives of the energy (nonlinear response) if usepead == 0. The directions for the derivatives are determined by rf2_pert1_dir and rf2_pert2_dir and prepanl as the following:
The computation of the 2^{nd} derivative of wavefunction with respect to “lambda_1” and “lambda_2” is computed if if rf2_pert1_dir[idir1] AND rf2_pert2_dir[idir2] are equal to 1, where “idir1” (“idir2”) is direction of the perturbation “lambda_1” (“lambda_2”). If ALL directions are activated (default behavior) AND prepanl == 1, then the code automatically selects only the directions that will be used by the nonlinear routine (optdriver == 5) using crystal symmetries.
rf2_pert1_dir¶
Mnemonics: Response Function (2^{nd} order Sternheimer equation): 1^{st} PERTurbation DIRection
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: (3)
Default value: [1, 1, 1]
Added in version: before_v9
Test list (click to open). Rarely used, [0/1027] in all abinit tests, [0/121] in abinit tutorials
Gives the directions of the 1^{st} perturbation to be considered when solving the 2^{nd} order Sternheimer equation. The three elements corresponds to the three primitive vectors, either in real space (phonon calculations), or in reciprocal space (\,d/ \,d k, homogeneous electric field, homogeneous magnetic field calculations). If equal to 1, the 2^{nd} order wavefunctions, as defined by rf2_dkdk or rf2_dkde, are computed for the corresponding direction. If 0, this direction is not considered. See rf2_dkdk for more details.
rf2_pert2_dir¶
Mnemonics: Response Function (2^{nd} order Sternheimer equation): 2^{nd} PERTurbation DIRection
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: (3)
Default value: [1, 1, 1]
Added in version: before_v9
Test list (click to open). Rarely used, [0/1027] in all abinit tests, [0/121] in abinit tutorials
Gives the directions of the 2^{nd} perturbation to be considered when solving the 2^{nd} order Sternheimer equation. The three elements corresponds to the three primitive vectors, either in real space (phonon calculations), or in reciprocal space (\,d/ \,d k, homogeneous electric field, homogeneous magnetic field calculations). If equal to 1, the 2^{nd} order wavefunctions, as defined by rf2_dkdk or rf2_dkde, are computed for the corresponding direction. If 0, this direction is not considered. See rf2_dkdk for more details.
rfasr¶
Mnemonics: Response Function: Acoustic Sum Rule
Mentioned in topic(s): topic_Phonons
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Rarely used, [4/1027] in all abinit tests, [0/121] in abinit tutorials
Control the evaluation of the acoustic sum rule in effective charges and dynamical matrix at Gamma within a response function calculation (not active at the level of producing the DDB, but at the level of the phonon eigenfrequencies output).
 0 → no acoustic sum rule imposed
 1 → acoustic sum rule imposed for dynamical matrix at Gamma, and charge neutrality imposed with extra charge evenly distributed among atoms
 2 → acoustic sum rule imposed for dynamical matrix at Gamma, and charge neutrality imposed with extra charge given proportionally to those atoms with the largest effective charge.
The treatment of the acoustic sum rule and charge neutrality sum rule is finer at the level of the ANADDB utility, with the two independent input variables asr and chneut.
rfatpol¶
Mnemonics: Response Function: ATomic POLarisation
Mentioned in topic(s): topic_DFPT, topic_Elastic, topic_Phonons
Variable type: integer
Dimensions: (2)
Default value: [1, 1]
Added in version: before_v9
Test list (click to open). Moderately used, [185/1027] in all abinit tests, [21/121] in abinit tutorials
 gpu: t01.in …
 libxc: t81.in, t82.in …
 mpiio: t51.in, t62.in, t62.in …
 paral: t53.in, t53.in, t53.in …
 seq: tsv4_80.in …
 tutoparal: tdfpt_04.in …
 tutorespfn: tdepes_1.in, tdepes_2.in, tdepes_3.in …
 v2: t01.in, t03.in, t04.in …
 v3: t02.in, t06.in, t07.in …
 v4: t02.in, t52.in, t60.in …
 v5: t21.in, t23.in, t24.in …
 v6: t35.in, t36.in, t37.in …
 v7: t43.in, t45.in, t50.in …
 v8: t07.in, t36.in, t41.in …
 v9: t41.in, t42.in, t50.in …
Control the range of atoms for which displacements will be considered in phonon calculations (atomic polarizations). These values are only relevant to phonon response function calculations. May take values from 1 to natom, with rfatpol (1)<= rfatpol (2). The atoms to be moved will be defined by the doloop variable iatpol:
 do iatpol= rfatpol (1), rfatpol (2)
For the calculation of a full dynamical matrix, use rfatpol (1)=1 and rfatpol (2)=natom, together with rfdir 1 1 1. For selected elements of the dynamical matrix, use different values of rfatpol and/or rfdir. The name ‘iatpol’ is used for the part of the internal variable ipert when it runs from 1 to natom. The internal variable ipert can also assume values larger than natom, denoting perturbations of electric field or stress type (see the DFPT help file).
rfddk¶
Mnemonics: Response Function with respect to Derivative with respect to K
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Rarely used, [10/1027] in all abinit tests, [0/121] in abinit tutorials
Activates computation of derivatives of ground state wavefunctions with respect to wavevectors. This is not strictly a response function but is a needed auxiliary quantity in the electric field calculations (see rfelfd). The directions for the derivatives are determined by rfdir.
 0 → no derivative calculation
 1 → calculation of first derivatives of wavefunctions with respect to k points (\,d/ \,d k calculation). The exact same functionality is provided by rfelfd = 2.
rfdir¶
Mnemonics: Response Function: DIRections
Mentioned in topic(s): topic_DFPT, topic_Elastic, topic_Phonons
Variable type: integer
Dimensions: (3)
Default value: [0, 0, 0]
Added in version: before_v9
Test list (click to open). Moderately used, [247/1027] in all abinit tests, [32/121] in abinit tutorials
 gpu: t01.in …
 libxc: t81.in, t82.in …
 mpiio: t51.in, t62.in, t62.in …
 paral: t06.in, t06.in, t06.in …
 seq: tsv2_82.in, tsv3_05.in, tsv4_55.in …
 tutoparal: tdfpt_04.in …
 tutorespfn: tdepes_1.in, tdepes_2.in, tdepes_3.in …
 v2: t01.in, t03.in, t04.in …
 v3: t02.in, t06.in, t07.in …
 v4: t02.in, t52.in, t56.in …
 v5: t05.in, t21.in, t23.in …
 v6: t06.in, t20.in, t35.in …
 v67mbpt: t52.in …
 v7: t03.in, t41.in, t43.in …
 v8: t07.in, t36.in, t41.in …
 v9: t41.in, t42.in, t50.in …
Gives the directions to be considered for response function calculations (also for the Berry phase computation of the polarization, see the berryopt input variable). The three elements corresponds to the three primitive vectors, either in real space (phonon calculations), or in reciprocal space (\,d/ \,d k, homogeneous electric field, homogeneous magnetic field calculations). So, they generate a basis for the generation of the dynamical matrix or the macroscopic dielectric tensor or magnetic susceptibility and magnetic shielding, or the effective charge tensors. If equal to 1, response functions, as defined by rfddk, rfelfd, rfphon, rfdir and rfatpol, are to be computed for the corresponding direction. If 0, this direction should not be considered.
rfelfd¶
Mnemonics: Response Function with respect to the ELectric FielD
Mentioned in topic(s): topic_EffectiveMass, topic_DFPT
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Moderately used, [106/1027] in all abinit tests, [16/121] in abinit tutorials
 libxc: t81.in, t82.in …
 mpiio: t62.in, t62.in, t69.in …
 paral: t54.in, t54.in, t54.in …
 seq: tsv3_05.in …
 tutorespfn: telast_2.in, teph_1.in, tlw_1.in …
 v2: t05.in, t06.in, t30.in …
 v3: t09.in, t16.in, t77.in …
 v4: t02.in, t52.in, t56.in …
 v5: t05.in, t23.in, t24.in …
 v6: t62.in, t63.in, t64.in …
 v67mbpt: t52.in …
 v7: t41.in, t43.in, t46.in …
 v8: t07.in, t47.in, t51.in …
 v9: t57.in …
Turns on electric field response function calculations. Actually, such calculations requires first the nonselfconsistent calculation of derivatives with respect to k, independently of the electric field perturbation itself.
 0 → no electric field perturbation
 1 → full calculation, with first the derivative of groundstate wavefunction with respect to k (\,d / \,d k calculation), by a nonselfconsistent calculation, then the generation of the firstorder response to an homogeneous electric field
 2 → only the derivative of groundstate wavefunctions with respect to k
 3 → only the generation of the firstorder response to the electric field, assuming that the data on derivative of groundstate wavefunction with respect to k is available on disk.
Note
Because the tolerances to be used for derivatives or homogeneous electric field are different, one often does the calculation of derivatives in a separate dataset, followed by calculation of electric field response as well as phonon. The options 2 and 3 proves useful in that context; also, in case a scissor shift is to be used, it is usually not applied for the \,d / \,d k response).
rfmagn¶
Mnemonics: Response Function with respect to MAGNetic Bfield perturbation
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Rarely used, [4/1027] in all abinit tests, [0/121] in abinit tutorials
rfmagn allows one to run response function calculations with respect to external magnetic field if set to 1. Currently, orbital magnetism is not taken into account and the perturbing potential has Zeeman form. For more details, see [Ricci2019].
rfmeth¶
Mnemonics: Response Function METHod
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: scalar
Default value: 1
Added in version: before_v9
Test list (click to open). Rarely used, [2/1027] in all abinit tests, [0/121] in abinit tutorials
Selects method used in response function calculations. Presently, only abs( rfmeth ) = 1 is allowed. This corresponds to storing matrix elements of the 2DTE computed using nonstationary expressions, instead of stationary ones.
The difference between positive and negative values is rather technical. Very often, the symmetries can be used in such a way that some matrix elements can be proven to be zero even without doing any computation. Positive values of rfmeth activate this use of symmetries, while it is denied when rfmeth is negative. There is an indirect additional outcome of this, as a symmetrization of the whole 2DTE is sometimes rendered possible when the additional knowledge of the zero matrix elements is available. Thus, the results obtained for positive and negative values of rfmeth might slightly differ for nonzero elements of the 2DTE, if they are computed in both cases.
rfphon¶
Mnemonics: Response Function with respect to PHONons
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Moderately used, [186/1027] in all abinit tests, [21/121] in abinit tutorials
 gpu: t01.in …
 libxc: t81.in, t82.in …
 mpiio: t51.in, t62.in, t62.in …
 paral: t53.in, t53.in, t53.in …
 seq: tsv4_80.in …
 tutoparal: tdfpt_04.in …
 tutorespfn: tdepes_1.in, tdepes_2.in, tdepes_3.in …
 v2: t01.in, t03.in, t04.in …
 v3: t02.in, t06.in, t07.in …
 v4: t02.in, t52.in, t60.in …
 v5: t21.in, t23.in, t24.in …
 v6: t35.in, t36.in, t37.in …
 v7: t43.in, t45.in, t50.in …
 v8: t07.in, t36.in, t41.in …
 v9: t41.in, t42.in, t50.in …
It must be equal to 1 to run phonon response function calculations.
rfstrs¶
Mnemonics: Response Function with respect to STRainS
Mentioned in topic(s): topic_DFPT, topic_Elastic
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Moderately used, [27/1027] in all abinit tests, [6/121] in abinit tutorials
 paral: t95.in, t95.in, t95.in …
 tutorespfn: telast_2.in, telast_5.in, telast_6.in …
 v4: t58.in, t59.in, t61.in …
 v7: t95.in, t96.in, t99.in …
 v8: t07.in …
Used to run strain responsefunction calculations (e.g. needed to get elastic constants). Define, with rfdir, the set of perturbations.
 0 → no strain perturbation
 1 → only uniaxial strain(s) (ipert=natom+3 is activated)
 2 → only shear strain(s) (ipert=natom+4 is activated)
 3 → both uniaxial and shear strain(s) (both ipert=natom+3 and ipert=natom+4 are activated)
See the possible restrictions on the use of strain perturbations, in the respfn help file.
rfuser¶
Mnemonics: Response Function, USERdefined
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Rarely used, [0/1027] in all abinit tests, [0/121] in abinit tutorials
Available to the developers, to activate the use of ipert=natom+6 and ipert=natom+7, two sets of perturbations that the developers can define.
 0 → no computations for ipert=natom+6 or ipert=natom+7
 1 → response with respect to perturbation natom+6 will be computed
 2 → response with respect to perturbation natom+7 will be computed
 3 → responses with respect to perturbations natom+6 and natom+7 will be computed
Important
In order to define and use correctly the new perturbations, the developer might have to include code lines or additional routines at the level of the following routines: dfpt_cgwf.F90, dfpt_dyout.F90, dfpt_symph.F90, dfpt_dyout.F90, dfpt_etot.F90, littlegroup_pert.F90, dfpt_looppert.F90, dfpt_mkcor.F90, dfpt_nstdy.F90, dfpt_nstwf.F90, respfn.F90, dfpt_scfcv.F90, irreducible_set_pert.F90, dfpt_vloca.F90, dfpt_vtorho.F90, dfpt_vtowfk.F90. In these routines, the developer should pay a particular attention to the rfpert array, defined in the routine respfn (in m_respfn_driver.F90), as well as to the ipert local variable.
smdelta¶
Mnemonics: SMeared DELTA function
Mentioned in topic(s): topic_TDepES
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Moderately used, [26/1027] in all abinit tests, [4/121] in abinit tutorials
 paral: t59.in, t59.in, t59.in …
 tutorespfn: tdepes_1.in, tdepes_2.in, tdepes_3.in …
 v5: t26.in …
 v6: t37.in, t50.in, t54.in …
 v7: t50.in, t51.in, t55.in …
When smdelta in nonzero, it will trigger the calculation of the imaginary part of the secondorder electronic eigenvalues, which can be related to the electronic lifetimes. The delta function is evaluated using:
 when smdelta == 1, FermiDirac smearing: \frac{0.25}{(cosh(\frac{x}{2.0}))^2}
 when smdelta == 2, Cold smearing by Marzari using the parameter a=0.5634 (minimization of the bump): \frac{e^{x^2}}{\sqrt{\pi}}\left(1.5+x(a\ 1.5+x(1.0+a\ x))\right)
 when smdelta == 3, Cold smearing by Marzari using the parameter a=0.8165 (monotonic function in the tail): as 2 but different a
 when smdelta == 4, Smearing of Methfessel and Paxton ([Methfessel1989]) with Hermite polynomial of degree 2, corresponding to “Cold smearing” of N. Marzari with a=0 (so, same smeared delta function as smdelta=2, with different a).
 when smdelta == 5, Gaussian smearing: \frac{e^{x^2}}{\sqrt{\pi}}
td_maxene¶
Mnemonics: TimeDependent dft: MAXimal kohnsham ENErgy difference
Mentioned in topic(s): topic_TDDFT
Variable type: real
Dimensions: scalar
Default value: 0.0
Added in version: before_v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [0/121] in abinit tutorials
 v1: t69.in
The Matrix to be diagonalized in the Casida framework (see [Casida1995]) is a NxN matrix, where, by default, N is the product of the number of occupied states by the number of unoccupied states. The input variable td_maxene allows one to diminish N: it selects only the pairs of occupied and unoccupied states for which the KohnSham energy difference is less than td_maxene . The default value 0.0 means that all pairs are taken into account. See td_mexcit for an alternative way to decrease N.
td_mexcit¶
Mnemonics: TimeDependent dft: Maximal number of EXCITations
Mentioned in topic(s): topic_TDDFT
Variable type: real
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Rarely used, [1/1027] in all abinit tests, [0/121] in abinit tutorials
 v1: t69.in
The Matrix to be diagonalized in the Casida framework (see [Casida1995]) is a NxN matrix, where, by default, N is the product of the number of occupied states by the number of unoccupied states. The input variable td_mexcit allows one to diminish N: it selects the first td_mexcit pairs of occupied and unoccupied states, ordered with respect to increasing KohnSham energy difference. However, when td_mexcit is zero, all pairs are allowed. See td_maxene for an alternative way to decrease N.
tim1rev¶
Mnemonics: TIMe 1^{st} order REVersal
Characteristics: DEVELOP
Mentioned in topic(s): topic_DFPT
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9
Test list (click to open). Rarely used, [3/1027] in all abinit tests, [0/121] in abinit tutorials
Allowed values are 0 or 1.
If tim1rev is equal to 1, the Sternheimer equation is solved simultaneously at +q and q perturbation wavevectors. The first order potential at q is taken to be equal to the Hermitian conjugate of the first order potential at +q. The wavefunctions from both +q and q are then combined to generate the first order density. Relevant in the case of magnetic field perturbation (but will be relevant also in case of nonzero frequency DFPT, when implemented).
usepead¶
Mnemonics: USE of PEAD formalism
Mentioned in topic(s): topic_nonlinear
Variable type: integer
Dimensions: scalar
Default value: 1
Only relevant if: optdriver == 5 (nonlinear response computations)
Added in version: before_v9
Test list (click to open). Rarely used, [9/1027] in all abinit tests, [0/121] in abinit tutorials
Determine which nonlinear implementation is used. If usepead =1, the Perturbation Expansion After Discretization formalism is used, as in [Veithen2005]. In that method, the electric field is treated numerically, i.e the kspace gradient operator appearing in the expression of the electric field potential is discretized (see Eq.7 and 10 of [Veithen2005]). If usepead =0, the electric field is treated analytically, leading to a better kpoints convergence. Furthermore, the current implementation is compatible with PAW pseudopentials, while usepead =1 is not. The drawback of the analytical method is one has to solve a second order Sternheimer equation before actually computing third derivatives of the energy, using rf2_dkdk and rf2_dkde. This is not the most timeconsumming part though. Look at the inputs of related tests in the testsuite to see examples of the workflow.