I've simulated the dielectric constants using the LEPSILON = .TRUE. tag and the PBE GPAW potentials. A collegue mentioned that for accurate results norm conserving pseudo-potentials are the way to go. I have two problems/questions now

  • Why would norm conserving potentials be better? I could not find any source verifying this.
  • How can I get the norm conserving potentials. I could not find them on the VASP download site anymore.
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    $\begingroup$ +1. Great first question! Welcome to the site and we hope to see more of your!!! $\endgroup$ – Nike Dattani May 24 at 16:49
  • $\begingroup$ The first part may be related to this question $\endgroup$ – Cody Aldaz May 24 at 16:50
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    $\begingroup$ I don't think Vasp has NCPPs anymore. At least I've not seen them in recent datasets they provide. It's entirely PAW datasets (strongly preferred) or USPPs. I'm not sure why you were recommended NCPPs since PAW potentials will have atom-corrections in dielectric calculations, and are in general very accurate in reference to all-electron calculations. $\endgroup$ – Anubhab Haldar May 25 at 9:02
  • $\begingroup$ @AnubhabHaldar I think NCPPs make many computations significantly easier. While I agree PAW is advantageous for being able to reconstruct the all-electron wavefunctions (which can be useful for other things) and are the most transferable, depending on the definition of accuracy (Delta gauge etc.) and how each potential is generated, NCPPs can be equally "accurate" with respect to the all-electron calculation. I guess what I mean is, a "good" NCPP is better than a "bad" PAW dataset. $\endgroup$ – Kevin J. M. May 28 at 3:09

I don't think there is a consensus of norm conserving PP being more accurate. There are some references I am aware of which have calculated dielectric tensor using NC-PP, but without justification though:

  • Yu, E. K.; Stewart, D. A.; Tiwari, S. Ab Initio Study of Polarizability and Induced Charge Densities in Multilayer Graphene Films. Phys. Rev. B - Condens. Matter Mater. Phys. 2008, 77 (19), 1–8.
  • Kumar, P.; Bhadoria, B. S.; Kumar, S.; Bhowmick, S.; Chauhan, Y. S.; Agarwal, A. Thickness and Electric-Field-Dependent Polarizability and Dielectric Constant in Phosphorene. Phys. Rev. B 2016, 93 (19), 1–8.

But then I have seen often (and performed calculations myself) PAW-based methods in VASP used for calculating the dielectric tensor. Here is a reference for you to dig deeper:

  • Laturia, A.; Van de Put, M. L.; Vandenberghe, W. G. Dielectric Properties of Hexagonal Boron Nitride and Transition Metal Dichalcogenides: From Monolayer to Bulk. npj 2D Mater. Appl. 2018, 2 (1), 6.

One way to validate your method is to compare polarizabilities (related to dielectric constant) with more accurate methods such as polarizability calculations using maximally localized Wannier functions - see below for some insights:

  • Pan, D.; Govoni, M.; Galli, G. Dielectric Properties of Condensed Systems Composed of Fragments. J. Chem. Phys. 2018, 149 (5), 051101.
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  • $\begingroup$ +1. Thanks for all the references gogo! $\endgroup$ – Nike Dattani May 28 at 0:34

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