Pseudopotentials

Currently PWscf and CP support both Ultrasoft (US) Vanderbilt pseudopotentials (PPs) and Norm-Conserving (NC) Hamann-Schlüter-Chiang PPs in separable Kleinman-Bylander form. Note however that calculation of third-order derivatives is not (yet) implemented with US PPs.

The Quantum-ESPRESSO package uses a unified pseudopotential format (UPF) (http://www.pwscf.org/format.htm) for all types of PPs, but still accepts a number of other formats:

• the ``old PWscf'' format for NC PPs (PWscf only!),
• the ``old CP'' format for NC PPs (CP only!),
• the ``old FPMD'' format for NC PPs (CP only!),
• the ``new PWscf'' format for NC and US PPs,
• the ``Vanderbilt'' format (formatted, not binary) for NC and US PPs.

See also http://www.pwscf.org/oldformat.htm.

A large collection of PPs (currently about 60 elements covered) can be downloaded from the Pseudopotentials Page of the Quantum-ESPRESSO web site (http://www.pwscf.org/pseudo.htm). The naming convention for these PPs is explained in file Doc/nomefile.upf.

If you do not find there the PP you need (because there is no PP for the atom you need or you need a different exchange-correlation functional or a different core-valence partition or for whatever reason may apply), it may be taken, if available, from published tables, such as e.g.:

• G.B. Bachelet, D.R. Hamann and M. Schlüter, Phys. Rev. B 26, 4199 (1982)
• X. Gonze, R. Stumpf, and M. Scheffler, Phys. Rev. B 44, 8503 (1991)
• S. Goedecker, M. Teter, and J. Hutter, Phys. Rev. B 54, 1703 (1996)

or otherwise it must be generated. Since version 2.1, Quantum-ESPRESSO includes a PP generation package, in the directory atomic/ (sources) and atomic_doc/ (documentation, tests and examples). The package can generate both NC and US PPs in UPF format. We refer to its documentation for instructions on how to generate PPs with the atomic/ code.

Other PP generation packages are available on-line:

• David Vanderbilt's code (UltraSoft PPs):
  http://www.physics.rutgers.edu/~dhv/uspp/index.html
• Fritz Haber's code (Norm-Conserving PPs):
  http://www.fhi-berlin.mpg.de/th/fhi98md/fhi98PP
• José-Luís Martins' code (Norm-Conserving PPs):
  http://bohr.inesc-mn.pt/~jlm/pseudo.html

The first two codes produce PPs in UPF format, or in a format that can be converted to unified format using the utilities of directory upftools/.

Finally, other electronic-structure packages (CAMPOS, ABINIT) provide tables of PPs that can be freely downloaded, but need to be converted into a suitable format for use with Quantum-ESPRESSO.

Remember: always test the PPs on simple test systems before proceeding to serious calculations.