SIESTA Pseudos and Basis Set Database

Pseudopotentials with © symbol are created and optimised by SIMUNE. We would appreciate for proper citation of this set: J. Oroya, A. Martín, M. Callejo, M.García-Mota, and F. Marchesin in “Pseudopotential and Numerical Atomic Orbitals Basis Dataset”, provided by SIMUNE Atomistics (www.simuneatomistics.com).

The rest of pseudopotentials is obtained from: https://departments.icmab.es/leem/SIESTA_MATERIAL/Databases/Pseudopotentials/periodictable-gga-abinit.html

Please log in and select the desired element from the periodic table. All registered users can download the optimised GGA-PBE* pseudopotentials and DZP basis sets**. Please contact us if you need a pseudopotential that is currently not available for download.

The .zip file contains:

• Pseudopotential file in .psf format. It is compatible with the stable version of SIESTA (4.0.2) as well as with the beta release (4.1-b4)
• Basis set block
• Graphics of the All Electron (AE) vs pseudo (PS) charge of the pseudopotential
• README.md file containing information about the electrons included in the code and valence of the pseudo potential

*PBE-GGA: Generalized Gradient Approximations of J. P. Perdew, K. Burke and M. Ernzerhof, Phys. Rev. Lett. 77, 3865 (1996)

**DZP: Double Zeta Polarization basis set

SIMUNE uses optimization procedures to generate high quality and high transferability pseudopotentials and corresponding basis sets. The pseudopotentials are created by minimizing the difference in the pseudopotential and all-electron energy between different electronic configurations. The optimization of the basis sets is based on the minimization of the average energy of a dimer system with different interatomic distances. This approach ensures the generation of a transferable basis set, and excellent performance in different environments (molecules and bulk). These pseudopotentials have been generated and then optimized using the GGA-PBE approximation, while the basis sets have been optimized specifically for corresponding pseudopotentials. We recommend to use a pseudopotential with corresponding basis set to avoid unphysical system behaviour.

The pseudopotential file (.psf format) has to be placed in the same folder with the input SIESTA .fdf file. It is necessary to have a pseudopotential file for each element included into the system of study.

The basis set block (block-PAO.basis-DZP) has to be included into the SIESTA .fdf input file. If the system of study contains several elements it is important to include the basis set for each of the them as it is shown below:

%block PAO.Basis
H 2
n=1 0 2 E 10 -0.7
10.0 5.0
n=1 1 1 E 10 -0.7 Q 2.0 1.0
10.0
Na 2
n=3 0 1 E 10 -0.7
10.0 5.0
n=3 1 1 E 10 -0.7 Q 2.0 1.0
10.0
%endblock PAO.Basis

The Δ-test is a benchmark test that has become very popular while comparing the accuracy of DFT codes, basis sets and pseudopotentials. The Δ-value quantifies the difference of the calculated Equation Of State (EOS) curve between a code (in this case SIESTA) and the reference code (WIEN2k). A Δ-value of 0 meV/atom would correspond to identical results between the codes.

Extended information on Δ-test can be found at https://dx.doi.org/10.1080/10408436.2013.772503, https://science.sciencemag.org/content/351/6280/aad3000 and https://molmod.ugent.be/deltacodesdft.

SIMUNE makes use of the Δ-test to evaluate the quality and the transferability of the optimized pseudopotentials and basis sets.*

* Although the Δ-test by itself does not indicate the transferability of a basis set (it is only performed for a specific system). However, due to the fact that the optimized basis sets are obtained from calculations on a molecule, the value is a good indicator of the basis set transferability. The SIESTA Δ-test values were calculated with optimized pseudopotentials and DZP basis sets. In general, better results (lower Δ-values) can be obtained by increasing the basis set multiplicity.