[CP2K-user] Question about usage of libxc

[Frederick Stein]

Dear Huang,

There are some examples with correlation functionals in the test suite 
(tests/QS/regtest-libxc/H2O-hybrid-b3lyp_libxc.inp). LibXC correlation 
functionals are treated like exchange functionals. Technically, there isn't 
any difference between calculating a LibXC exchange or correlation or 
kinetic energy functional of the same kind.

RPBE affects only the enhancement factor of the exchange part. The LDA 
exchange energy density is known analytically. For the correlation part, 
you have to manually add the PBE correlation functional. The LibXC 
implementation and our implementation, both exploit the PW92 LDA functional.

The input section looks like the following

&XC_FUNCTIONAL
  &LIBXC
    FUNCTIONAL XC_GGA_X_RPBE
  &END LIBXC
  &LIBXC
    FUNCTIONAL XC_GGA_C_PBE
  &END LIBXC
&END XC_FUNCTIONAL

or with the cp2k implementation of PBE

&XC_FUNCTIONAL
  &LIBXC
    FUNCTIONAL XC_GGA_X_RPBE
  &END LIBXC
  &PBE
# We don't need PBE exchange here because we are using RPBE exchange
    SCALE_X 0.0
  &END PBE
&END XC_FUNCTIONAL

I hope I could help you.

Best,

Frederick
yk... at gmail.com schrieb am Freitag, 14. August 2020 um 06:15:02 UTC+2:

> Greetings, cp2k users.
>
> I want to use rpbe functional in my calculation, after reading manual I 
> find I should use libxc cuz rpbe is not implemented directly in cp2k. 
> However, when I am reading input files in test/, I find there are examples 
> in which only exchange term is defined, so I wonder how will cp2k calculate 
> the correlation term? Will it use original LDA?
> Answers will be appreciated, thanks in advance. 
>
> Huang Yike 
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.cp2k.org/archives/cp2k-user/attachments/20200814/384705db/attachment.htm>