ABINIT, developper input variables:

Governs the method of access to the internal wavefunction files. Relevant only for the wavefunctions files for which the corresponding "mkmem"-type variable is zero, that is, for the wavefunctions that are not kept in core memory.

• 0 => Use standard Fortran IO routines
• 1 => Use MPI/IO routines
• 2 => Directly use NetCDF routines (this option is not available)
• 3 => Use ETSF_IO routines, creating NetCDF files according to the ETSF specification.

• "Specification of an extensible and portable file format for electronic structure and crystallographic data", X. Gonze, C.-O. Almbladh, A. Cucca, D. Caliste, C. Freysoldt, M. Marques, V. Olevano, Y. Pouillon, M.J. Verstraete, Comput. Mat. Science 43, 1056 (2008)
• "Sharing electronic structure and crystallographic data with ETSF_IO", D. Caliste, Y. Pouillon, M.J. Verstraete, V. Olevano, X. Gonze, Comput. Physics Communications 179, 748 (2008)
• see also http://www.etsf.eu/fileformats.

Control the size of the block in the LOBPCG algorithm. This keyword works only with paral_kgb=1 and has to be either 1 or a multiple of 2.

-- With npband=1:

• 1 => band-per-band algorithm
• n => The minimization is performed using nband/n blocks of n bands.

• 1 => The minimization is performed using nband/npband blocks of npband bands.
• n => The minimization is performed using nband/(npband*n) blocks of npband*n bands.

Flag to read/write Occupations as computed in DMFT. This flag is useful to restart a DFT+DMFT calculation with self-consistency over electronic density. The occupations are written each time a DMFT loop is finished. So if the calculations stops because the time limit is reached, this option offers the possibility to restart the self-consistent loop over density at the point where it stopped.

• 0=> Occupations are written but never read.
• 1=> Occupations are read from I_DMFTOCCND, where I is the root for input files.
• 2=> Occupations are read from O_DMFTOCCND, where O is the root for output files.

Choice of solver for the Impurity model.

• 1=> LDA+U self-energy is used (for testing purpose)
• 2=> Hubbard one solver.

This keyword is irrelevant when Fast Fourier Transforms are done using Graphics Processing Units (GPU), i.e. when use_gpu_cuda=1 (in that case, it is ignored).

Allows to choose the algorithm for Fast Fourier Transforms. These have to be used when applied to wavefunctions (routine fourwf.f), as well as when applied to densities and potentials (routine fourdp.f). Presently, it is the concatenation of three digits, labelled (A), (B) and (C).

The first digit (A) is to be chosen among 1, 2, 3 and 4 :

• 1=> use FFT routines written by S. Goedecker.
• 2=> use machine-dependent FFT algorithm, taken from the vendor library, if it exists and if it has been implemented. The bare fftalg=200 has little chance to be faster than fftalg=112, but it might be tried. Implementing library subroutines with fftalg/=200 has not yet been done. Currently implemented library subroutines (fftalg=200) are:
  • on HP, z3dfft from Veclib;
  • on DEC Alpha, zfft_3d from DXML;
  • on NEC, ZFC3FB from ASL lib;
  • on SGI, zfft3d from complib.sgimath
• 3=> use serial or multi-threaded FFTW fortran routines (http://www.fftw.org). Currently implemented with fftalg=300.
• 4=> use FFT routines written by S. Goedecker, 2002 version, that will be suited for MPI and OpenMP parallelism.

• 0=> only use Complex-to-complex FFT
• 1=> real-to-complex is also allowed (only coded for A==1)

• 0=> no use of zero padding
• 1=> use of zero padding (only coded for A==1 and A==4)
• 2=> use of zero padding, and also combines actual FFT operations (using 2 routines from S. Goedecker) with important pre- and post-processing operations, in order to maximize cache data reuse. This is very efficient for cache architectures. (coded for A==1 and A==4, but A==4 is not yet sufficiently tested)

Option for LOB algorithm, used in the band/FFT/k-point parallelisation, see npband, npfft, npkpt, and paral_kgb.

• =1 : old implementation
• =2 : new implementation : the calls to getghc are made in parallel on a set of bands nbdblock : the aim is to reduce the number of collective communications. This is not yet implemented in lobpcgwf.

Only relevant if use_gpu_cuda=1, that is, if ABINIT is used with CUDA functionality.

Use of linear algebra and matrix algebra on GPU is only efficient if the size of the involved matrices is large enough. The gpu_linalg_limit parameter defines the threshold above which linear (and matrix) algebra operations are done on the Graphics Processing Unit.
The considered matrix size is equal to:

Choice for the method used to solve the Dyson equation in the calculation of the interacting susceptibility matrix or/and in the calculation of the ACFD exchange-correlation energy:

• idyson=1 : Solve the Dyson equation by direct matrix inversion
• idyson=2 : Solve the Dyson equation as a first-order differential equation with respect to the coupling constant lambda - only implemented for the RPA at the present stage (see header of dyson_de.f for details)
• idyson=3 : Calculate only the diagonal of the interacting susceptibility matrix by self-consistently computing the linear density change in response to a set of perturbations. Only implemented for the RPA at the present stage, and entirely experimental (see dyson_sc.f for details).

Define the HXC kernel, in the cases for which it can be dissociated with the choice of the HXC functional given by ixc, namely the TD-DFT computation of excited states (iscf=-1), and the computation of the susceptibility matrix (for ACFD purposes). Options 2 to 6 are for the ACFD only.

• 0 => RPA for the TDDFT but no kernel for the ACFD (testing purposes).
• 1 => RPA for the TDDFT and ACFD.
• 2 => ALDA (PW92) for the ACFD
• 3 => PGG for the ACFD [M. Petersilka, U.J. Gossmann and E.K.U. Gross, PRL 76,1212 (1996)]
• 4 => BPG for the ACFD. This amounts to half the PGG kernel plus half the ALDA kernel for spin-compensated systems [K. Burke, M. Petersilka and E.K.U. Gross, in "Recent Advances in Density Functional Methods", Vol. III, edited by P. Fantucci and A. Bencini (World Scientific, Singapore, 2002)]
• 5 => Linear energy optimized kernel [J. Dobson and J. Wang, PRB 62, 10038 (2000)]
• 6 => Non-linear energy optimized kernel [J. Dobson and J. Wang, PRB 62, 10038 (2000)]

• 0=> do "usual" xc quadrature on fft grid
• 1=> do higher accuracy xc quadrature using fft grid and additional points at the centers of each cube (doubles number of grid points)--the high accuracy version is only valid for boxcut>=2. If boxcut < 2, the code stops.

NOTE : NOT USED AT PRESENT (v5.3.0)

This variable is a bit-wise combination of what will be written into / read from a special WFK/DEN/POT file. The contents of the file follow the Nanoquanta/ETSF file format specifications.

Please check the "etsf_io" module of the ETSF I/O library for possible values.

NOTE : NOT USED AT PRESENT (v5.3.0)

This variable tells what will be written into / read from a special WFK/DEN/POT file. The contents of the file follow the Nanoquanta/ETSF file format specifications.

Please check the "etsf_io" module of the ETSF I/O library for possible values.

Used when iscf>0, to define:
- the way a change of density is derived from a change of atomic position,
- the way forces are corrected when the SCF cycle is not converged.

Supported values :

• 0 => density not changed (fixed charge), forces not corrected
• 1 => density not changed, forces corrected with rigid ion hypothesis (atomic charge moved with atom)
• 2 => density changed and forces corrected with rigid ion hypothesis (atomic charge moves with atom)
• 3 => density changed and forces corrected with a different implementation of the rigid ion hypothesis
• 4 => density not changed, forces corrected with the use of Harris functional formula (*)
• 5 => density changed using D. Alfe 2nd-order algorithm (**), forces not corrected
• 6 => density changed using D. Alfe 2nd-order algorithm (**) and forces corrected with the use of Harris functional formula (*)

Used when iscf>0, to define the SCF preconditioning scheme. Potential-based preconditioning schemes for the SCF loop are still under development.
The present parameter (force constant part) describes the way a change of force is derived from a change of atomic position.
Supported values :

• 0 => hessian is the identity matrix
• 1 => hessian is 0.5 times the identity matrix
• 2 => hessian is 0.25 times the identity matrix
• -1=> hessian is twice the identity matrix
• ... (simply corresponding power of 2 times the identity matrix)

For the time being, only used when imgmov=9 (Langevin Path-Integral Molecular Dynamics).
irandom defines the random number generator.

Supported values :

• 1 => "uniformrandom", delivered with ABINIT package (initially comes from numerical receipies).
• 2 => intrinsic Fortran 90 random number generator.
• 3 => "ZBQ" non-deterministic random number generator by R. Chandler and P. Northrop. (This was delivered for free at http://www.ucl.ac.uk/~ucakarc/work/index.html#code", but the latter address does not seem to work anymore. In any case, the initial copyright is not violated by the files/documentation present in the ABINIT package).

Control the way the wavefunction for each k-point is stored inside ABINIT, in reciprocal space.
For the GS calculations, in the "cg" array containing the wavefunction coefficients, there is for each k-point and each band, a segment cg(1:2,1:npw). The 'full' number of plane wave is determined by ecut. However, if the k-point coordinates are build only from zeroes and halves (see list below), the use of time-reversal symmetry (that connects coefficients) has been implemented, in order to use real-to-complex FFTs (see fftalg), and to treat explicitly only half of the number of plane waves (this being used as 'npw').
For the RF calculations, there is not only the "cg" array, but also the "cgq" and "cg1" arrays. For the time-reversal symmetry to decrease the number of plane waves of these arrays, the q vector MUST be (0 0 0). Then, for each k point, the same rule as for the RF can be applied.
WARNING (991018) : for the time being, the time-reversal symmetry cannot be used in the RF calculations.

• 1=> do NOT take advantage of the time-reversal symmetry
• 2=> use time-reversal symmetry for k=( 0 0 0 )
• 3=> use time-reversal symmetry for k=(1/2 0 0 )
• 4=> use time-reversal symmetry for k=( 0 0 1/2)
• 5=> use time-reversal symmetry for k=(1/2 0 1/2)
• 6=> use time-reversal symmetry for k=( 0 1/2 0 )
• 7=> use time-reversal symmetry for k=(1/2 1/2 0 )
• 8=> use time-reversal symmetry for k=( 0 1/2 1/2)
• 9=> use time-reversal symmetry for k=(1/2 1/2 1/2)
• 0=> (preprocessed) for each k point, choose automatically the appropriate time-reversal option when it is allowed, and chose istwfk=1 for all the other k points.

Sets proper input values for the determination of U and J i.e. for pawujat (first atom treated with PAW+U), irdwfk (=1), tolvrs (=10^(-8)), nstep (=255), diemix (=0.45), atvshift (pawujat) pawujv). Do not overwrite these variables manually unless you know what you do.

• macro_uj=1 (and nsppol=2) Standard procedure to determine U on atom pawujat through a shift of the potential on both spin channels.
• macro_uj=1 (and nsppol=1) Non standand procedure to determine U from potential shift on atom pawujat (experimental).
• macro_uj=2 (and nsppol=2) Non standand procedure to determine U from potential shift on atom pawujat through a shift on spin channel 1 on this atom and the response on this channel (experimental).
• macro_uj=3 (and nsppol=2) Standand procedure to determine J from potential shift on spin channel 1 on atom pawujat and response on spin channel 2 (experimental).

In case of non-standard, blocked algorithms for the optimization of the wavefunctions (that is, if wfoptalg=4):

• if wfoptalg=4, nbdblock defines the number of blocks (the number of bands in the block is then nband/nbdblock ).

When nctime is non-zero, the molecular dynamics information is output in NetCDF format, every nctime time step. Here is the content of an example file :

netcdf md32.outH_moldyn1 {
dimensions:
        time = UNLIMITED ; // (11 currently)
        DimTensor = 6 ;
        DimCoord = 3 ;
        NbAtoms = 32 ;
        DimVector = 3 ;
        DimScalar = 1 ;
variables:
        double E_pot(time) ;
                E_pot:units = "hartree" ;
        double E_kin(time) ;
                E_kin:units = "hartree" ;
        double Stress(time, DimTensor) ;
                Stress:units = "hartree/Bohr^3" ;
        double Position(time, DimCoord, NbAtoms) ;
                Position:units = "Bohr" ;
        double Celerity(time, DimCoord, NbAtoms) ;
                Celerity:units = "Bohr/(atomic time unit)" ;
        double PrimitiveVector1(DimVector) ;
        double PrimitiveVector2(DimVector) ;
        double PrimitiveVector3(DimVector) ;
        double Cell_Volume(DimScalar) ;
                Cell_Volume:units = "Bohr^3" ;
}

Number of points to be added to lambda=0 and lambda=1 (that are always calculated for the integration ober the coupling constant lambda in the ACFD calculation of the exchange-correlation energy.

• ndyson=-1 : let the code decide how many points to use (presently, 3 points for idyson=1 or 3, and 9 points for idyson=2)
• ndyson=0 : only compute the non-interacting and fully-interacting susceptibility matrices.
• ndyson>0 : use ndyson more points in ]0,1[

Allows to choose the algorithm for non-local operator application. On super-scalar architectures, the Default nloalg=4/14 is the best, but you can save memory by using nloalg=-4.
More detailed explanations:

Defines whether the atomic wave function (used as projectors in PAW+U) should be renormalized to 1 within PAW sphere.

• normpawu=0 : leave projector
• normpawu=1 : renormalize

Needed only when iscf=7 or 17.

Gives the number of previous iterations involved in Pulay mixing (mixing during electronic SC iterations).



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Only relevant (for Ground-State calculations) when paral_kgb=1 and LOBPCG algorithm is used.
When using Scalapack (or any similar Matrix Algebra library), it is well known that the efficiency of the eigenproblem resolution saturates as the number of CPU cores increases. It is better to use a smaller number of CPU cores for the LINALG calls.
This maximum number of cores can be set with np_slk.
A large number for np_slk (i.e. 1000000) means that all cores are used for the Linear Algebra calls.



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This variable controls the order of used scaling functions when the Hartree potential is computed using the Poisson solver (see icoulomb imput variable). This variable is of seldom use since the default value is large enough. Nonetheless, possible values are 8, 14, 16, 20, 24, 30, 40, 50, 60, 100. Values greater than 20 are included in ABINIT for test purposes only.



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Allows to choose the algorithm for orthogonalisation.
Positive or zero values make two projections per line minimisation, one before the preconditioning, one after. This is the clean application of the band-by-band CG gradient for finding eigenfunctions.
Negative values make only one projection per line mininisation.
The orthogonalisation step is twice faster, but the convergence is less good. This actually calls to a better understanding of this effect.
ortalg=0, 1 or -1 is the conventional coding, actually identical to the one in versions prior to 1.7
ortalg=2 or -2 try to make better use of existing registers on the particular machine one is running.
More demanding use of registers is provided by ortalg=3 or -3, and so on.
The maximal value is presently 4 and -4.
Tests have shown that ortalg=2 or -2 is suitable for use on the available platforms.



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PAPI aims to provide the tool designer and application engineer with a consistent interface and methodology for use of the performance counter hardware found in most major microprocessors. PAPI enables software engineers to see, in near real time, the relation between software performance and processor events.
This option can be used only when ABINIT has been compiled with the --enable-papi configure option.
If papiopt=1, then PAPI counters are used instead of the usual time() routine. All the timing output of ABINIT is then done with PAPI values. The measurements are more accurate and give also access to the flops of the calculation.



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Forces the output of the all-electron wavefunction for only a single band. To be used in conjuction with:
pawprtwf=1 and pawprt_k. The indexing of the bands start with one for the lowest occupied band and goes up from there.



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Forces the output of the all-electron wavefunction for only a single k-point. To be used in conjuction with:
pawprtwf=1 and pawprt_b. The indexing follows the order in ouptput of the internal variable kpt in the beginning of the run.



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Determines the atom for which U (or J) should be determined. See also macro_uj.



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The sphere radius serves to extrapolate the U value calculated at r_paw to a larger sphere radius. See also macro_uj. As most projector functions are localized within r_paw to ≈80%, 20 a.u. contains ≈100% of the wavefunction and corresponds to r_paw → ∞.



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Amplitude of the potential shift for the determination of U (or J). See also macro_uj.



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Print PCINFO, PHFREQ, and PHVEC files, for use with self-consistent phonon runs, after a perturbation calculation. Only prints out files for the present q-point, and there is presently no tool to symmetrize or merge these files, so use anaddb instead (with prtscphon input variable). The abinit input variable is destined to someday bypass the use of anaddb for scphon calculations.



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Print out geometry (_BLZTRP_GEOM) and eigenenergy (_BLZTRP_EIGEN) files for the BoltzTraP code by Georg Madsen.



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If set to 1, a CIF file is output with the crystallographic data for the present run (cell size shape and atomic positions).



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Print out dipole of unit cell, calculated in real space for the primitive cell only. Under development.



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If set to 1, the nesting function for the k-point grid is printed. For the moment the path in q space for the nesting function is fixed, but will become an input as well.



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Print out VASP-style POSCAR and FORCES files, for use with PHON or frophon codes for frozen phonon calculations. See the associated script in ~abinit/extras/post_processing/phondisp2abi.py for further details on interfacing with PHON, PHONOPY, etc...



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Used in Recursion method (tfkinfunc=2). In the first SCF calculation it fixes the initial guess for the Fermi energy.



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Used in Recursion method (tfkinfunc=2). It represents the ratio of the two grid step: recgratio=fine_step/coarse_step and it is bigger or equal than 1. It introduces a double-grid system which permits to compute the electronic density on a coarse grid, using a fine grid (defined by ngfft) in the discretisation of the green kernel (see recptrott). Successively the density and the recursion coefficients are interpolated on the fine grid by FFT interpolation. Note that ngfft/recgratio=number of points of the coarse grid has to be compatible with the parallelization parameters.



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Used in Recursion method (tfkinfunc=2). Determine the number of discretisation points to compute some path integral in the recursion method ; those path integrals are used to compute the entropy and the eigenvalues energy. during the latest SFC cycles.



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Used in Recursion method (tfkinfunc=2). Determine the maximum order of recursion, that is the dimension of the krylov space we use to compute density. If the precision setten by rectolden is reached before that order, the recursion method automatically stops.



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Used in Recursion method (tfkinfunc=2). Determine the trotter parameter used to compute the exponential of the hamiltonian in the recursion method: exp(-beta*(-Delta + V)) ~ (exp(-beta/(4*recptrott) V) exp(-beta/(4*recptrott) Delta) exp(-beta/(4*recptrott) V))^(2*recptrott). If set to 0, we use recptrott = 1/2 in the above formula. Increasing recptrott improve the accuracy of the trotter formula, but increase the dicretisation error: it may be necessary to increase ngfft. The discretisation error is essentially the discretisation error of the green kernel exp((recptrott/beta*|r|^2)) on the ngfft grid.



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Used in Recursion method (tfkinfunc=2). Used to improve the computational time in the case of the recursion method in a large cell: the density at a point will be computed with taking account only of a sphere of radius recrcut.



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Used in Recursion method (tfkinfunc=2). It is used to test an electron gas by putting the ion potential equal to zero.



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Used in Recursion method (tfkinfunc=2). Sets a tolerance for differences of electronic density that, reached TWICE successively, will cause one SCF cycle to stop. That electronic density difference is computed in the infinity norm (that is, it is computed point-by-point, and then the maximum difference is computed).



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Not applicable for RPA (as there should be a Kxc present). Initially tested for ikhxc==2 (ALDA).



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Note : this feature exist because in a previous status of the GW calculations, non-symmorphic symmetry operations could not be exploited. Thus, the k points were restricted to the IBZ. In order to prepare GW calculations, and to perform GW calculations, symmorphi=0 was to be used, together with nsym=0.



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Sets a tolerance for the ratio of differences of eigenenergies in the line minisation conjugate-gradient algorithm. It compares the decrease of the eigenenergy due to the last line minimisation, with the one observed for the first line minimisation. When the ratio is lower than tolrde, the next line minimisations are skipped.
The number of line minimisations is limited by nline anyhow.
This stopping criterion is present for both GS and RF calculations. In RF calculations, tolrde is actually doubled before comparing with the above-mentioned ratio, for historical reasons.



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If set to 1, enable the use of ScaLapack within LOBPCG.



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If set to 1, enable the use of LDA+DMFT, see in particular the important variables dmft_solv, dmftbandi, dmftbandf, dmft_nwli, dmft_nwlo, dmft_tollc, and dmft_iter. DMFT is currently available for collinear (nspinor=1) polarized or unpolarized calculations (nspden=nsppol=2 or nspden=nsppol=1) and for non collinear calculations (nspinor=2,nspden=4,nsppol=1). However it is not yet available for collinear antiferromagnetic calculations (nspden=2,nsppol=1) and non collinear non magnetic calculations (nspden=1, nsppol=1,nspinor=2). Only static calculations without relaxation or dynamics are possible. Relevant quantity from converged DMFT calculations are total energy and spectral function. Total and partail spectral functions can be obtained with prtdos=1 and can be found in files OUTSpFunc* (where OUT is the root for output files). (see Amadon, B., Lechermann, F., Georges, A., Jollet, F., Wehling, T. O., and Lichtenstein, A. I. Phys. Rev. B 77(20), (2008) and B Amadon 2012 J. Phys.: Condens. Matter 24 075604 )



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These are user-definable integers which the user may input and then utilize in subroutines of his/her own design. They are not used in the official versions of the ABINIT code, and should ease independent developments (hopefully integrated in the official version afterwards).
Internally, they are available in the dtset structured datatype, e.g. dtset%useria .



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These are user-definable with the same purpose as useri.



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The absolute value of vdw_nfrag is the number of vdW interacting fragments in the unit cell. As wannierization takes place in reciprocal space, the MLWF center positions could be translated by some lattice vector from the cell where atoms are placed. If vdw_nfrag >= 1 then MLWFs are translated to the original unit cell, otherwise the program will keep the positions obtained by Wannier90. The later is usually correct if some atoms are located at the corners or at limiting faces of the unit cell. Used only if vdw_xc=10,11.



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Used only when Van der Waals DFT-D2 correction is activated (vdw_xc=5).
The DFT-D2 (S. Grimme approach) dispersion potential is implemented as a pair potential. The number of pairs of atoms contributing to the potential is necessarily limited. To be included in the potential a pair of atom must have contribution to the energy larger than vdw_tol.



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This array defines the interacting fragments by assigning to each atom an integer index from 1 to vdw_nfrag. The ordering of vdw_typfrag is the same as typat or xcart. Internally each MLWF is assigned to a given fragment by computing the distance to the atoms. MLWFs belong to the same fragment as their nearest atom. The resulting set of MLWFs in each interacting fragment can be found in the output file in xyz format for easy visualization. Used only if vdw_xc=10,11.



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Set of dimensionless positive numbers which define the maximum multiples of the primitive translations (rprimd) in the supercell construction. Each component of vdw_supercell indicates the maximum number of cells along both positive or negative directions of the corresponding primitive vector i.e. the components of rprimd. In the case of layered systems for which vdW interactions occur between layers made of tightly bound atoms, the evaluation of vdW corrections comming from MLWFs in the same layer (fragment) must be avoided. Both a negative or null value for one component of vdw_supercell will indicate that the corresponding direction is normal to the layers. Used only if vdw_xc=10,11.



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It has been observed that the SCF cycle of the Tran-Blaha mGGA can be quite hard to make converge, for systems for which there is some vacuum. In this case, setting xc_denpos to 1.0e-7 ... 1.0e-6 has been seen to allow good convergence. Of course, this will affect the numerical results somehow, and one should play a bit with this value to avoid incorrect calculations.



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xc_tb09_c
Mnemonics: Value of the c parameter in the eXchange-Correlation TB09 functional
Characteristic:
Variable type: real
Default is all 99.99d0

The modified Becke-Johnson exchange-correlation functional by Tran and Blaha (Phys. Rev. Lett. 102, 226401 (2009)) reads :

V_x(r) = c * V_x^{BR}(r) + (3*c - 2) * 1/pi * sqrt(5/12) * sqrt(2*kden(r)/den(r))

in which V_x^{BR}(r) is the Becke-Roussel potential.

In this equation the parameter c can be evaluated at each SCF step according to the following equation :

c = alpha + beta * sqrt(1/V_{cell} * \int_{V_{cell}} |grad(den(r))|/den(r) d3r)

The c parameter is evaluated thanks to the previous equation when xc_tb09_c is equal to the "magic" default value 99.99. The c parameter can also be fixed to some (property-optimized or material-optimized) value by using this variable.



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