# PAW settings

### This page gives hints on how to set parameters for a PAW calculation with the ABINIT package.

##### Copyright (C) 2016-2017 ABINIT group (FJ)

Mentioned in topic_Planewaves, help_features#2.3.

### Table of content:

- 1. Introduction.
- 2. Related lesson(s) of the tutorial.
- 3. Related input variables.
- 4. Selected input files.
- 5. References.

### 1. Introduction.

The PAW atomic data can be used with plane waves as well as with wavelets. Specificities of PAW for use with planewaves are presented here. See topic_Wavelets for its use with wavelets.

The way the PAW method is implemented with planewaves in ABINIT is described in [Torrent2008].
The use of PAW atomic data (equivalent to pseudopotential file for the norm-conserving case) automatically launch a PAW calculation. ABINIT is provided with the JTH [Jollet2014] PAW atomic data table on the ABINIT web site.
To perform a standard PAW calculation, the input file is the same than for a norm-conserving one, except that the variable pawecutdg must be specified (see below). In the case the input variable accuracy is used, the input variable pawecutdg is automatically used.
Some physical functionalities are available only in the PAW framework: DFT+U, DMFT, local exact exchange,...

Go to the top

### 2. Related lesson(s) of the tutorial.

- The lesson on the use of PAW (PAW1) presents the Projector-Augmented Wave method, implemented in ABINIT as an alternative to norm-conserving pseudopotentials, with a sizeable accuracy and CPU time advantage.
- The lesson on the generation of PAW atomic data files (PAW2) presents the generation of atomic data for use with the PAW method. Prerequisite : PAW1.
- The lesson on the validation of a PAW atomic datafile (PAW3) demonstrates how to test a generated PAW dataset using ABINIT, against the ELK all-electron code, for diamond and magnesium. Prerequisite : PAW1 and PAW2.
Go to the top

### 3. Related input variables.

Compulsory input variables:

... pawecutdg [PAW - Energy CUToff for the Double Grid]

Useful input variables:

... ngfftdg [Number of Grid points for Fast Fourier Transform : Double Grid]
... pawfatbnd [PAW: print band structure in the FAT-BaND representation]
... pawovlp [PAW - spheres OVerLaP allowed (in percentage)]
... pawprtden [PAW: PRinT total physical electron DENsity]
... pawprtdos [PAW: PRinT partial DOS contributions]
... pawprtwf [PAW: PRinT WaveFunctions]
... pawspnorb [PAW - option for SPiN-ORBit coupling]
... pawxcdev [PAW - choice for eXchange-Correlation DEVelopment (spherical part)]
... usepawu [USE PAW+U (spherical part)]
... usexcnhat [USE eXchange-Correlation with NHAT (compensation charge density)]

Relevant internal variables:

... %usepaw [USE Projector Augmented Waves method]

Input variables for experts:

... bxctmindg [BoX CuT-off MINimum for the Double Grid (PAW)]
... mqgriddg [Maximum number of Q-wavevectors for the 1-dimensional GRID for the Double Grid in PAW]
... pawcpxocc [PAW - use ComPleX rhoij OCCupancies]
... pawlcutd [PAW - L angular momentum used to CUT the development in moments of the Densitites]
... pawlmix [PAW - maximum L used in the spherical part MIXing]
... pawmixdg [PAW - MIXing is done (or not) on the (fine) Double Grid]
... pawnhatxc [PAW - Flag for exact computation of gradients of NHAT density in eXchange-Correlation.]
... pawnphi [PAW - Number of PHI angles used to discretize the sphere around each atom.]
... pawntheta [PAW - Number of THETA angles used to discretize the sphere around each atom.]
... pawnzlm [PAW - only compute Non-Zero LM-moments of the contributions to the density from the spheres]
... pawoptmix [PAW - OPTion for the MIXing of the spherical part]
... pawprt_b [PAW PRinT band]
... pawprt_k [PAW PRinT K-point]
... pawprtvol [PAW: PRinT VOLume]
... pawstgylm [PAW - option for the STorage of G_l(r).YLM(r)]
... pawsushat [PAW - SUSceptibility, inclusion of HAT (compensation charge) contribution]
... pawusecp [PAW - option for the USE of CPrj in memory (cprj=WF projected with NL projector)]
... spnorbscl [SPin-ORBit SCaLing]
Go to the top

### 4. Selected input files.

WARNING : as of ABINITv8.6.x, the list of input files provided in the specific section of the topics Web pages is still to be reviewed/tuned. In some cases, it will be adequate, and in other cases, it might be incomplete, or perhaps even useless.
The user can find some related example input files in the ABINIT package in the directory /tests, or on the Web:

tests/v4/Input: t06.in t08.in t17.in t94.in

tests/v5/Input: t06.in t11.in t17.in t20.in
Go to the top

### 5. References.

[Jollet2014] F. Jollet, M. Torrent and N. Holzwarth, "Generation of Projector Augmented-Wave atomic data: a 71 element validated table in the XML format", Comp. Phys. Comm. 185, 1246-1254 (2014).
[Torrent2008] Marc Torrent, François Jollet, François Bottin, Gilles Zérah and Xavier Gonze, "Implementation of the projector augmented-wave method in the ABINIT code: Application to the study of iron under pressure", Computational Materials Science 42, 337 - 351 (2008).
DOI: 10.1016/j.commatsci.2007.07.020.

Go to the top