The degree of compatibility with LibXC / other functionals

[andrewshyichuk]

What is your suggested feature? Please describe.

The code requires libxc, it thus must call libxc. If it calls libxc for PW91 LDA - it can call it for any other LDA, am I right? The same goes for GGA, and hybrids. Or, does it not?

Describe the solution you'd like

I'd like to use PBEsol at least, and general libxc input at best (e.g. XC_GGA_X_PBE_SOL+XC_GGA_C_PBE_SOL).

Edit Modified the two files below, adding a functional was straightforward. sktwocnt/lib/xcfunctionals.f90 sktwocnt/lib/twocnt.f90

Do I assume correctly that, from purely physical point of view, there is no fundamental difference in which GGA do I use? I mean, as long as the functional itself is sane, the SK files and the respective DFTB calculation would be sane as well?

[vanderhe]

Hi @andrewshyichuk,

while slateratom and sktwocnt are interfaced with libXC, we only support a limited number of xc-functionals. An extension of this list in principle is straight-forward and requires changes to all three components: sktools, slateratom, and sktwocnt. So modifying the two files listed above does not suffice. I don't think we will support general libXC inputs any time soon, but adding e.g. PBEsol shouldn't be too involved.

Do I assume correctly that, from purely physical point of view, there is no fundamental difference in which GGA do I use?

Yes, that is correct. From a technical point of view one has to be careful, especially with hybrids as you are responsible to admix the correct amount of (range-separated) Fock exchange.

Best regards Tammo