mirror of https://github.com/abinit/abinit.git
97 lines
4.3 KiB
Markdown
97 lines
4.3 KiB
Markdown
---
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description: How to master the use of norm-conserving pseudopotentials and PAW atomic data, and their consequences
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authors: XG
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---
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<!--- This is the source file for this topics. Can be edited. -->
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This page gives hints on how to master the use of norm-conserving pseudopotentials and PAW atomic data, and
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their consequences with the ABINIT package.
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## Introduction
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ABINIT can read many different types of norm-conserving (NC) pseudopotentials and
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PAW atomic data. The names of the files to be used in an ABINIT run are to be
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provided in the input file, one for each [[topic:AtomTypes|type of atom]].
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The list of pseudopotentials with the [[pseudos]] input variable and (optionally)
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the directory where all pseudos are located with [[pp_dirpath]].
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Note that one **cannot mix** NC pseudopotentials with PAW atomic data files in a single ABINIT run,
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even for different datasets. One has to stick either to NC pseudopotentials or to PAW.
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The ultrasoft formalism is not implemented.
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**Norm-conserving pseudopotential tables**
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There are several sets of NC pseudopotentials available for most
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elements of the periodic table, either in LDA or in GGA-PBE. The
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[[https://www.abinit.org/psp-tables|recommended one]]
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(GGA-PBE, [[ixc]]=11) comes from the ONCVPSP generator.
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For the formalism please consult [[cite:Hamann2013]].
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The generation and validation of the table is discussed in [[cite:Setten2018]].
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[Other tables](https://www.abinit.org/atomic-data-files) are also available.
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The Goedecker HGH table (e.g. LDA, [[ixc]]=1), also including spin-orbit
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is rather accurate, but requires often large
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[[ecut]]. The old Troullier-Martins type tables
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are deprecated, because not accurate enough, and also not
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including spin-orbit coupling. The different formats for norm-conserving
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pseudopotentials are described in the Pseudos page of the [developers section](/developers/psp8_info/)
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A much more flexible and powerful file format (PSML) has been recently proposed in [[cite:Garcia2018]].
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The format is supported by Abinit via the psml library that must be activated by user during
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the configuration of the package.
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Abinit can read NC pseudos in different formats, including the psp8 format and
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the UPF1 and UPF2 formats. The ONCVPSP generator can produce pseudopotentials in these different formats.
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THe UPF2 format has the advantage that is contains atomic orbitals, from which ABINIT can compute a
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initial Hamiltonian, diagonalize it, and thus, generate a rather good starting density and potential.
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Activate this using [[wfinit]]=2 .
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However, ultrasoft or PAW pseudos in UPF1/UPF2 format are not supported.
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**PAW atomic data tables**
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Five large sets of PAW atomic data can be read by ABINIT. The
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[[https://www.abinit.org/psp-tables|JTH table]]
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is recommended (GGA-PBE, [[ixc]]=11).
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It uses the PAW-XML format.
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[Others](https://www.abinit.org/atomic-data-files) are also available.
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**Validation**
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Many pseudopotentials (NC as well as PAW) have been tested
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against all-electron calculations, see the section "Documents and tools"
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paragraph about the "Delta" project on
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[[https://www.abinit.org/downloads/PAW2|the ABINIT web site PAW
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page]]. In [[tutorial:paw3]] it is explained How to perform more detailed
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comparisons with an all-electron code.
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**Generation**
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Six codes are available to generate new pseudopotentials when needed, see
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[[https://www.abinit.org/atomic-data-files|the related ABINIT web
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page]]. For norm-conserving pseudopotentials, ONCVPSP is the preferred one.
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The ultra-soft pseudopotentials generated by "USPP" are approximations of the
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Projector Augmented Wave approach, and are treated within the PAW framework in
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ABINIT. The ATOMPAW generator is actually tightly connected to ABINIT such
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that there are ABINIT automatic tests in which a PAW atomic data is generated,
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and then used in ABINIT. There is also a dedicated tutorial to ATOMPAW/ABINIT.
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**Miscellaneous**
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Norm-conserving pseudopotentials can be mixed, to generate "alchemical"
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pseudoatoms, see [[topic:AtomTypes]].
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This feature is not available for PAW.
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## Related Input Variables
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{{ related_variables }}
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## Selected Input Files
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{{ selected_input_files }}
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## Tutorials
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* [[tutorial:paw2|Second tutorial on the projector-augmented wave technique]] The generation of atomic data.
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* [[tutorial:paw3|Third tutorial on the projector-augmented wave technique]] Testing PAW datasets against an all-electron code.
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