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vdw input variables

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

irdvdw

Mnemonics: Integer that governs the ReaDing of _VDW files
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc > 0, to read previously calculated vdW-DF variables. Supported values:

  • 0: do not read vdW-DF variables
  • 1: read vdW-DF variables

prtvdw

Mnemonics: PRinT Van Der Waals file
Characteristics: DEVELOP
Mentioned in topic(s): topic_printing
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Print out a NetCDF file containing a vdW-DF kernel.

vdw_df_acutmin

Mnemonics: vdW-DF MINimum Angular CUT-off
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 10
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build angular meshes for the vdW-DF kernel.

vdw_df_aratio

Mnemonics: vdW-DF Angle RATIO between the highest and lowest angles.
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 30
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build angular meshes for the vdW-DF kernel.

vdw_df_damax

Mnemonics: vdW-DF Delta for Angles, MAXimum
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 0.5
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build angular meshes for the vdW-DF kernel.

vdw_df_damin

Mnemonics: vdW-DF Delta for Angles, MINimum
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 0.01
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build angular meshes for the vdW-DF kernel.

vdw_df_dcut

Mnemonics: vdW-DF D-mesh CUT-off
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 30
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build the vdW-DF kernel.

vdw_df_dratio

Mnemonics: vdW-DF, between the highest and lowest D, RATIO.
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 20
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build the vdW-DF kernel.

vdw_df_dsoft

Mnemonics: vdW-DF Distance for SOFTening.
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 1.0
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build the vdW-DF kernel.

vdw_df_gcut

Mnemonics: vdW-DF G-space CUT-off
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 5
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to filter the vdW-DF kernel in reciprocal space.

vdw_df_ndpts

Mnemonics: vdW-DF Number of D-mesh PoinTS
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: integer
Dimensions: scalar
Default value: 20
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build the vdW-DF kernel.

vdw_df_ngpts

Mnemonics: vdW-DF Number of G-mesh PoinTS
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: integer
Dimensions: scalar
Default value: -1
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build the vdW-DF kernel.

vdw_df_nqpts

Mnemonics: vdW-DF Number of Q-mesh PoinTS
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: integer
Dimensions: scalar
Default value: 30
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build the vdW-DF kernel.

vdw_df_nrpts

Mnemonics: vdW-DF Number of R-PoinTS
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: integer
Dimensions: scalar
Default value: 2048
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to define the sampling of the vdW-DF-kernel in real-space.

vdw_df_nsmooth

Mnemonics: vdW-DF Number of SMOOTHening iterations
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: integer
Dimensions: scalar
Default value: 12
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to exponentially smoothen q near q0.

vdw_df_phisoft

Mnemonics: vdW-DF PHI value SOFTening.
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: -1.0
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build the vdW-DF kernel.

vdw_df_qcut

Mnemonics: vdW-DF Q-mesh CUT-off
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 5
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build the vdW-DF kernel.

vdw_df_qratio

Mnemonics: vdW-DF, between highest and lowest Q, RATIO.
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 20
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0,.

vdw_df_rcut

Mnemonics: vdW-DF Real-space CUT-off
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 100
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to define the vdW-DF kernel cut-off radius.

vdw_df_rsoft

Mnemonics: vdW-DF radius SOFTening.
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 0.0
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build the vdW-DF kernel.

vdw_df_threshold

Mnemonics: vdW-DF energy calculation THRESHOLD
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 0.01
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Sets a threshold for the energy gradient that, when reached, will cause the vdW-DF interactions to be calculated. Adjust it to a big value (e.g. 1e12) to enable it all along the SCF calculation. Too small values, as well as negative values, will result in the vdW-DF energy contributions never being calculated.

vdw_df_tolerance

Mnemonics: vdW-DF global TOLERANCE.
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 1e-13
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build the vdW-DF kernel.

vdw_df_tweaks

Mnemonics: vdW-DF TWEAKS.
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: integer
Dimensions: scalar
Default value: 0
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, to build the vdW-DF kernel.

Important

Modifying this variable will likely transform the calculated energies and their gradients into garbage. You have been warned!

vdw_df_zab

Mnemonics: vdW-DF ZAB parameter
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: -0.8491
Only relevant if: vdw_xc>0
Added in version: before_v9

Test list (click to open). Rarely used, [0/1087] in all abinit tests, [0/148] in abinit tutorials

Used when vdw_xc>0, as introduced in [Dion2004].

vdw_nfrag

Mnemonics: Van Der Waals Number of interacting FRAGments
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: integer
Dimensions: scalar
Default value: 1
Only relevant if: vdw_xc in [10,11]
Added in version: before_v9

Test list (click to open). Rarely used, [3/1087] in all abinit tests, [0/148] in abinit tutorials

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.

vdw_supercell

Mnemonics: Van Der Waals correction from Wannier functions in SUPERCELL
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: integer
Dimensions: (3)
Default value: [0, 0, 0]
Only relevant if: vdw_xc in [10,11]
Added in version: before_v9

Test list (click to open). Rarely used, [3/1087] in all abinit tests, [0/148] in abinit tutorials

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 coming 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.

vdw_tol

Mnemonics: Van Der Waals TOLerance
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: 1e-10
Only relevant if: vdw_xc == 5
Added in version: before_v9

Test list (click to open). Rarely used, [4/1087] in all abinit tests, [0/148] in abinit tutorials

The DFT-D methods [Grimme2010] dispersion potentials, vdw_xc == 5 or 6 or 7, include 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 .

vdw_tol_3bt

Mnemonics: Van Der Waals TOLerance for 3-Body Term
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: real
Dimensions: scalar
Default value: -1
Comment: Do include the 3-body term in the correction
Only relevant if: vdw_xc == 6
Added in version: before_v9

Test list (click to open). Rarely used, [1/1087] in all abinit tests, [0/148] in abinit tutorials

Control the computation of the 3-body correction inside DFT-D3 dispersion correction (Grimme approach) to the total energy:

  • If vdw_tol_3bt <0, no 3-body correction.
  • If vdw_tol_3bt >0, the 3-body term is included with a tolerance = vdw_tol_3bt.

DFT-D3 as proposed by S. Grimme adds two contributions to the total energy in order to take into account of the dispersion:

  • A pair-wise potential for which the tolerance is controlled by vdw_tol

  • A 3-body term which is obtained by summing over all triplets of atoms. Each individual contribution depends of the distances and angles between the three atoms. As it is impossible to sum over all the triplets in a periodic system, one has to define a stopping criterium which is here that an additional contribution to the energy must be higher than vdw_tol_3bt

The last term has been predicted to have an important effect for large molecules [Grimme2010]. It is however quite costly in computational time for periodic systems and seems to lead to an overestimation of lattice parameters for weakly bound systems [Grimme2011]. Still, its contribution to energy, to forces and to stress is available (not planned for elastic constants, dynamical matrix and internal strains).

vdw_typfrag

Mnemonics: Van Der Waals TYPe of FRAGment
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: integer
Dimensions: (natom)
Default value: 1 * natom
Only relevant if: vdw_xc in [10,11]
Added in version: before_v9

Test list (click to open). Rarely used, [3/1087] in all abinit tests, [0/148] in abinit tutorials

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.

vdw_xc

Mnemonics: Van Der Waals eXchange-Correlation functional
Characteristics: DEVELOP
Mentioned in topic(s): topic_vdw
Variable type: integer
Dimensions: scalar
Default value: 0
Added in version: before_v9

Test list (click to open). Rarely used, [7/1087] in all abinit tests, [0/148] in abinit tutorials

Selects a van-der-Waals density functional to apply the corresponding correction to the exchange-correlation energy. If set to zero, no correction will be applied. Possible values are:

  • 0: no correction.
  • 1: apply vdW-DF1 (DRSLL) from [Dion2004].
  • 2: apply vdw-DF2 (LMKLL) from [Lee2010].
  • 5: apply vdw-DFT-D2 as proposed by S. Grimme [Grimme2006] (adding a semi-empirical dispersion potential). Available only for ground-state calculations and response functions; see vdw_tol variable to control convergence.
  • 6: apply vdw-DFT-D3 as proposed by S. Grimme [Grimme2010] (refined version of DFT-D2). Available only for ground-state calculations and response functions; see vdw_tol variable to control convergence and vdw_tol_3bt variable to include 3-body corrections.
  • 7: apply vdw-DFT-D3(BJ) as proposed by Grimme (based on Becke-Jonhson method from [Becke2006]). Available only for ground-state calculations and response functions; see vdw_tol variable to control convergence.
  • 10: evaluate the vdW correlation energy from maximally localized Wannier functions, as proposed by P. L. Silvestrelli, also known as vdW-WF1 method [Silvestrelli2008]. For details on this implementation please check [Espejo2012]. The improvements introduced by Andrinopoulos et al. [Andrinopoulos2011], namely the amalgamation procedure, splitting of p-like MLWFs into two s-like Wannier functions and fractional occupation of MLWFs are performed automatically.
  • 11: evaluate the vdW correlation energy from maximally localized Wannier functions, as proposed by A. Ambrosetti and P. L. Silvestrelli, also known as vdW-WF2 method [Ambrosetti2012].
  • 14: apply DFT/vdW-QHO-WF method as proposed by Silvestrelli, which combines the quantum harmonic oscillator-model with localized Wannier functions [Silvestrelli2013]. For periodic systems a supercell approach has to be used since vdw_supercell is not enabled in this case.

For vdw_xc = 1 and vdw_xc = 2, the implementation follows the strategy devised in the article of Roman-Perez and Soler [Romanperez2009].