[CP2K-user] [CP2K:13668] SCAN XC density functional: Do we have to use specific PSEUDOPOTENTIALS for SCAN? Are they available?

[Thomas Kühne]

Dear Vyacheslav and Tian, 

the usage of post-GGA functionals involves the calculation of \nabla n 
and nasty derivatives of the form \partial e^{XC} / \partial \nabla n, 
which gives rise to strong so-called „ringing effects“. 
To avoid the latter a number of smoothing operators such as NN10, 
SPLINE3, etc. are provided, whose numerical derivatives assume less 
continuity. Many of these smoothing operators also have a favorable 
convergence behavior wrt to the density cutoff, which otherwise would 
require rather high values to filter out the highest frequencies. 

Greetings, 
Thomas

> Am 27.07.2020 um 03:56 schrieb Vyacheslav Bryantsev <vyachesla... at gmail.com>:
> 
> Dear Tian and CP2K developers,
> 
> I confirm for my system, which is a concentrated  aqueous salt, these options work with  CUTOFF=800 and it would probably work at smaller values also.
>         &XC_GRID
> 
>                XC_DERIV NN10_SMOOTH
> 
>                XC_SMOOTH_RHO NN10
> 
>         &END XC_GRID
> Interestingly, removing them requires CUTOFF of at least 1200.
> A question to developers: What do these parameters do and what do those specific options mean?
> There is very little information in the manual about these options.
> 
> Thank you
> Slava
> Vyacheslav Bryantsev
> 
> On Thursday, June 4, 2020 at 6:22:38 AM UTC-4, Hua Tian wrote:
> Dear Prof. Hutter and Bryantsev,
> In my FPMD simulations for aqueous solutions by using SCAN functional (with the MOLOPT-SR basis sets and the GTH  pseudopotentials for SCAN from the website in your e-mail.), I found that smoothing methods (e.g., &XC_GRID / XC_DERIV NN10_SMOOTH / XC_SMOOTH_RHO NN10 / &END XC_GRID) was probably important for the convergence of SCF. For a simulation using SCAN functional with CUTOFF 400 that SCF did not converge, adding the &XC_GRID part methoned above made the SCF converge. However, I did not know if this setting would influence the accuracy of simulations.
> Sincerely, 
> Tian Hua
> 
> 
> 在 2020年4月10日星期五 UTC+8下午6:31:42，jgh写道：
> Hi 
> 
> 1) Many people have used PBE pp previously. 
>    SCAN optimized pp can be found at 
>    https://github.com/juerghutter/GTH/blob/master/SCAN/POTENTIAL <https://github.com/juerghutter/GTH/blob/master/SCAN/POTENTIAL> 
> 2) Newly published SCAN parameters for D3 are available in the current 
>    version of CP2K from Github. For older version you need to 
>    add a line in the input with the parameters. 
> 3) Use very high cutoffs, depending on your system. If the cutoff is not 
>    high enough SCF will not converge smoothly to a low value (10^-7 in OT). 
>    I don't have experience if the smoothing methods work to reduce the cutoff. 
> 
> regards 
> 
> Juerg Hutter 
> -------------------------------------------------------------- 
> Juerg Hutter                         Phone : ++41 44 635 4491 
> Institut für Chemie C                FAX   : ++41 44 635 6838 
> Universität Zürich                   E-mail: h... at chem.uzh.ch <> 
> Winterthurerstrasse 190 
> CH-8057 Zürich, Switzerland 
> --------------------------------------------------------------- 
> 
> -----c... at googlegroups.com <> wrote: ----- 
> To: "cp2k" <c... at googlegroups.com <>> 
> From: "Vyacheslav Bryantsev" 
> Sent by: c... at googlegroups.com <> 
> Date: 04/09/2020 04:50PM 
> Subject: [CP2K:13100] SCAN XC density functional: Do we have to use specific PSEUDOPOTENTIALS for SCAN? Are they available? 
> 
> Dear CP2K Community, 
> 
> Is there a set or recommended setting for using SCAN in cp2k? 
> 
> More specifically, 
> 1. Can we use PBE pseudopotentials for SCAN or this is a bad idea? If not, where one can find specific pseudopotentials reparametrized for SCAN? 
> 2. Does the D3 correction work automatically now with SCAN. If not, how to specify it? 
> 3. Recommendations for grid when using SCAN 
> 
> Thank you, 
> Slava   
> 
> 
>   
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==============================
Thomas D. Kühne
Dynamics of Condensed Matter
Chair of Theoretical Chemistry
University of Paderborn
Warburger Str. 100
D-33098 Paderborn
Germany
tdku... at mail.upb.de
+49/(0)5251/60-5726

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