9
$\begingroup$

I am a beginner and newly started running DFT calculations to find out the electronic band structure of certain materials in Quantum ESPRESSO. But we have to select the pseudopotential for running the SCF loop. There are lots of pseudopotential files(.UPF format) available on the internet for the same material. Which is quite confusing for me to select which one I Should use. How they are different from one another? Does it depend on the type of calculation we are going to perform or which property of materials we are looking for? Can I generate a pseudopotential file by myself? If yes, how.

Please, Clarify my doubts! It will be helpful to me in my learning process. Thanks!

$\endgroup$
  • $\begingroup$ +1. Welcome to our community, and thank you for contributing your excellent question here! We hope to see much more of you !!! $\endgroup$ – Nike Dattani Sep 21 at 18:48
6
$\begingroup$

How to choose pseudopotential for DFT calculations in Quantum ESPRESSO?

You can find almost all the pseudopotentials (PP) from the following website for all elements in the periodical table.

Currently, there are four parameters that you can choose.

  1. type: NC(Scalar and FR version)/PAW
  2. XC: LDA/PBE/PBEsol
  3. accuracy: standard/stringent
  4. format: upf/html/psp8/psml/djrepo

How they differ from one another? Does it depend on the type of calculation we are going to perform or which property of materials we are looking for?

Yes, it depends on the materials that you are modeling. There are many things that need to be considered in the generated PP and hence differ. For example, the spin-orbit coupling (SOC) should be included or not. If you consider SOC, you should use the FR version. Which method is utilized to generate this PP? It is differed by PAW and NC.

Can I generate a pseudopotential file by myself?

Yes, you can. BUT as a beginner, I strongly recommend you use the existed PP database.

| cite | improve this answer | |
$\endgroup$
  • $\begingroup$ Thanks! it is helpful. $\endgroup$ – Ujjawal M. Sep 23 at 5:55
4
$\begingroup$

The Materials Cloud Initiative has provided a very useful tool, the Standard solid-state pseudopotentials (SSSP), as

A standard solid-state pseudopotentials (SSSP) library optimized for precision and efficiency.

The two libraries (SSSP Precision and SSSP Efficiency) cover for each element either the best in class (among many libraries, or generated by us), or occasionally allow for a compromise (either expensive and accurate, or less expensive and a bit less accurate).

The convergence pattern of each element includes for each of the considered family (represented by a color): the total number of electrons in the valence, Z; delta value (the error in the equation of state compared with all-electron WIEN2k results, developed by Cottenier group), at full converged cutoff; the largest phonon frequency, ωmax, at the zone boundary (as a number), at full cutoff; and then as a function of wave function cutoff: the discrepancy of all phonon frequencies, δω̄, at the zone boundary, with respect to the converged value; the convergence of the pressure, δVpress, with respect to the converged value; the convergence of the cohesive energy, δEcoh, with respect to the converged value; the convergence of the band's structure, η10, and max η10 with respect to the converged value.

enter image description here

They also provided the calculated band structures, as a reference against several pseudo-potential libraries. It is a very good starting point when starting the choice of pseudo-potential.

| cite | improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.