[ase-users] Range parameter for the Tkatchenko-Scheffler dispersion correction

[Miguel Caro]

Hi all,

I wanted to use RPBE with Tkatchenko-Scheffler dispersion corrections
and couldn't find optimal s_R parameters in the literature. They have
been obtained by Marom et al [JCTC 7, 3944 (2011)] for a few hybrid and
meta-GGA functionals, but s_R parameters for the regular GGAs are
nowhere to be found in the literature. So I optimized these parameters
with GPAW using the S22 test set (as has been done before, for example
in the Marom paper and the original TS paper). Since doing one is the
same as doing seven I calculated them for all the GGAs whose alias is
recognized by GPAW (that is, they don't require explicit libXC naming to
work).

At the moment, s_R is hard-coded in ASE, and defaults to the PBE value
(self.sR = 0.94 in ase/calculators/vdwcorrection.py). This looks quite
inflexible. However a very simple solution would be to pass the xc value
to vdWTkatchenko09prl() and then look it up in a dictionary, and use the
optimal s_R value for a specific xc if it is in the dictionary:

    sR_opt = {"PBE": 0.940, "RPBE": 0.590, "revPBE": 0.585, "PBEsol":
    1.055, "BLYP": 0.625, "AM05": 0.840, "PW91": 0.965}

    self.sR = sR_opt[xc]

The dictionary above (sR_opt) contains the values for the 7 GGAs that I
have optimized.

I hope these values are useful to someone.

Regards,
Miguel
-- 
*Dr. Miguel Caro*
/Postdoctoral researcher/
Department of Electrical Engineering and Automation,
and COMP Centre of Excellence in Computational Nanoscience
Aalto University, Finland
Personal email: *mcaroba at gmail.com*
Work: *miguel.caro at aalto.fi*
Website: http://mcaroba.dyndns.org
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listserv.fysik.dtu.dk/pipermail/ase-users/attachments/20170403/b565a845/attachment.html>