How to use NC_K variable correctly? about vaspsol

[rhennig]

The variable NC_K describes indeed the cutoff charge density. This variable is described in the two papers on the solvation model:

Implicit solvation model for density-functional study of nanocrystal surfaces and reaction pathways. K. Mathew, R. Sundararaman, K. Letchworth-Weaver, T. A. Arias, and R. G. Hennig. J. Chem. Phys. 140, 084106 (2014), doi:10.1063/1.4865107.

Implicit self-consistent description of electrolyte in plane-wave density-functional theory. K. Mathew and R. G. Hennig,
Please let us know if you have any further questions.
arXiv:1601.03346 (2016).

Look for the equation for the shape function where the cutoff charge density parameter is used normalized the charge density inside the error function.

We find that it is numerical more stable to change SIGMA_K when modifying the solvation model and to leave the variable NC_K at its default value.

I hope this helps.

Best regards,
Richard Hennig

Richard G. Hennig
Associate Professor
Materials Science and Engineering, University of Florida
Adjunct Professor
Materials Science and Engineering, Cornell University
Email: [email protected]
Web: http://hennig.mse.ufl.edu

On Oct 28, 2016, at 5:53 AM, Fly330 [email protected] wrote:

As shown in Fig.1, I find a variable NC_K, the critical of charge density in VASPsol OUTCAR file.
https://cloud.githubusercontent.com/assets/21698419/19802178/0b52e656-9d35-11e6-95c5-219329596fd4.jpg
Fig.1
It isn't reported in USAGE.md file. Whether does the NC_K variable represent cutoff charge density of the total solid-liquid system or cutoff charge density of empty space not occupied by the metal slab only? Could you introduce the NC_K variable in detail? And how to use NC_K correctly?
Many thanks!
Yuan

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[Fly330]

Hi Prof. Hennig,
Thank you for your paper “Implicit self-consistent description of electrolyte in plane-wave density-functional theory”, as mentioned last time. The NC_K and SIGMA_K parameters have been correctly applied in my electrochemical simulations. In this paper, the computing PZCs of various metallic slabs agree well with experimental values. It is exciting and inspires me to repeat your results. However, I’m not sure how to correctly calculate the surface charge density? Could you please help me to solve this problem? If the problem were hard to explain briefly, could you please recommend me relevant papers or programs? Many thanks!
Best Regards,
Yuan

[rhennig]

Hi Yuan,

Remember that for metals the charge will be located on the surface. The surface charge density is simply the total charge of the slab divided by the total surface area, i.e. 2 x a x b for a rectangular unit cell.

Best regards,
Richard

On Nov 13, 2016, at 3:55 AM, Fly330 <[email protected]mailto:[email protected]> wrote:

Hi Prof. Hennig,
Thank you for your paper “Implicit self-consistent description of electrolyte in plane-wave density-functional theory”, as mentioned last time. The NC_K and SIGMA_K parameters have been correctly applied in my electrochemical simulations. In this paper, the computing PZCs of various metallic slabs agree well with experimental values. It is exciting and inspires me to repeat your results. However, I’m not sure how to correctly calculate the surface charge density? Could you please help me to solve this problem? If the problem were hard to explain briefly, could you please recommend me relevant papers or programs? Many thanks!
Best Regards,
Yuan

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