---
description: How to master the use of norm-conserving pseudopotentials and PAW atomic data, and their consequences
authors: XG
---
<!--- This is the source file for this topics. Can be edited. -->

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 [[topic:AtomTypes|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
[[https://www.abinit.org/psp-tables|recommended one]]
(GGA-PBE, [[ixc]]=11) comes from the ONCVPSP generator.
For the formalism please consult [[cite:Hamann2013]]. 
The generation and validation of the table is discussed in [[cite:Setten2018]].

[Other tables](https://www.abinit.org/atomic-data-files) 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](/developers/psp8_info/)
A much more flexible and powerful file format (PSML) has been recently proposed in [[cite:Garcia2018]].
The format is supported by Abinit via the psml library that must be activated by user during 
the configuration of the package.

!!! important

    Abinit can read NC pseudos in UPF1 format but not pseudos written following the 
    more recent UPF2 specifications.
    Also, 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
[[https://www.abinit.org/psp-tables|JTH table]]
is recommended (GGA-PBE, [[ixc]]=11).                
It uses the PAW-XML format.
[Others](https://www.abinit.org/atomic-data-files) 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
[[https://www.abinit.org/downloads/PAW2|the ABINIT web site PAW
page]]. In [[tutorial:paw3]] 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
[[https://www.abinit.org/atomic-data-files|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.

## Related Input Variables

{{ related_variables }}

## Selected Input Files

{{ selected_input_files }}

## Tutorials

* [[tutorial:paw2|Second tutorial on the projector-augmented wave technique]] The generation of atomic data. 
* [[tutorial:paw3|Third tutorial on the projector-augmented wave technique]] Testing PAW datasets against an all-electron code.

