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PseudosPAW

This page gives hints on how to master the use of norm-conserving pseudopotentials and PAW atomic data, and their consequences with the ABINIT package.

Introduction

ABINIT can read many different types of norm-conserving (NC) pseudopotentials and PAW atomic data. The names of the files to be used in an ABINIT run are to be provided in the input file, one for each type of atom. The list of pseudopotentials with the pseudos input variable and (optionally) the directory where all pseudos are located with pp_dirpath.

Note that one cannot mix NC pseudopotentials with PAW atomic data files in a single ABINIT run, even for different datasets. One has to stick either to NC pseudopotentials or to PAW. The ultrasoft formalism is not implemented.

Norm-conserving pseudopotential tables

There are several sets of NC pseudopotentials available for most elements of the periodic table, either in LDA or in GGA-PBE. The recommended one (GGA-PBE, ixc=11) comes from the ONCVPSP generator. For the formalism please consult [Hamann2013]. The generation and validation of the table is discussed in [Setten2018].

Other tables are also available. The Goedecker HGH table (e.g. LDA, ixc=1), also including spin-orbit is rather accurate, but requires often large ecut. The old Troullier-Martins type tables are deprecated, because not accurate enough, and also not including spin-orbit coupling. The different formats for norm-conserving pseudopotentials are described in the Pseudos page of the developers section A much more flexible and powerful file format (PSML) has been recently proposed in [Garcia2018]. The format is supported by Abinit via the psml library that must be activated by user during the configuration of the package.

Abinit can read NC pseudos in different formats, including the psp8 format and
the UPF1 and UPF2 formats. The ONCVPSP generator can produce pseudopotentials in these different formats. THe UPF2 format has the advantage that is contains atomic orbitals, from which ABINIT can compute a initial Hamiltonian, diagonalize it, and thus, generate a rather good starting density and potential. Activate this using wfinit=2 .

However, ultrasoft or PAW pseudos in UPF1/UPF2 format are not supported.

PAW atomic data tables

Five large sets of PAW atomic data can be read by ABINIT. The JTH table is recommended (GGA-PBE, ixc=11).
It uses the PAW-XML format. Others are also available.

Validation

Many pseudopotentials (NC as well as PAW) have been tested against all-electron calculations, see the section “Documents and tools” paragraph about the “Delta” project on the ABINIT web site PAW page. In paw3 tutorial it is explained How to perform more detailed comparisons with an all-electron code.

Generation

Six codes are available to generate new pseudopotentials when needed, see the related ABINIT web page. For norm-conserving pseudopotentials, ONCVPSP is the preferred one. The ultra-soft pseudopotentials generated by “USPP” are approximations of the Projector Augmented Wave approach, and are treated within the PAW framework in ABINIT. The ATOMPAW generator is actually tightly connected to ABINIT such that there are ABINIT automatic tests in which a PAW atomic data is generated, and then used in ABINIT. There is also a dedicated tutorial to ATOMPAW/ABINIT.

Miscellaneous

Norm-conserving pseudopotentials can be mixed, to generate “alchemical” pseudoatoms, see topic_AtomTypes. This feature is not available for PAW.

compulsory:

  • ntypat Number of TYPes of AToms
  • znucl charge -Z- of the NUCLeus

useful:

  • wfinit WaveFunctions INITialization

expert:

  • npsp Number of PSeudoPotentials to be read

internal:

  • %ziontypat Z (charge) of the IONs for the different TYPes of AToms

Selected Input Files

No input file associated to this topic.

Tutorials