[CP2K-user] [CP2K:18242] Re: QS Method, Basis, Potential and settings for organic molecules

DMT dobromirak at gmail.com
Thu Dec 22 10:59:16 UTC 2022


I kind of did a lot of digging and came up with the following general 
inputs for PBE and PBE0 for organic, non-periodic systmes.
What do you think ?

Can I optimize them further ?

I guess the system is too small (Li near cyclohexadiene, 14 atoms) to 
properly test the cutoff in
                    POTENTIAL_TYPE TRUNCATED    !TRUNCATED 1/r (Coulomb) 
                    CUTOFF_RADIUS 6.0            !SHOULD BE < HALF THE CELL
                    T_C_G_DATA /home/lsd/cp2k_data/t_c_g.dat     !DATA FOR 


                !    CUTOFF_RADIUS 6.0
                !    SCALE_X 0.25
                !&END PBE_HOLE_T_C_LR

but quite frankly even on a larger and periodic system (graphene) there 
seems to be no speed up.

The EPS_SCHWARZ is set to 1.0E-6 either way.

Best Regards,

On Tuesday, December 20, 2022 at 3:56:32 PM UTC+2 DMT wrote:

> Hello,
> I am interested in organic molecules, which are to be eventually modeled 
> over surfaces, in solvents in reactions and also in molecular crystals. I 
> am new to the software, so I have questions regarding choice of QS METHOD, 
> BASIS_SET, POTENTIALS and some settings. I have found a few input files, 
> searched the group (some google) and the manual, but there are quite a few 
> things I am not familiar with.
> For basis sets I search the cp2k/data directory of the source code and I 
> search the Basis Set Exchange web site. 
> - are there other ways of finding basis sets +/- potentials ?
> So far I am left with the impression that all GTH-POTENTIALs are only 
> available optimized for certain DFT functionals and are hence unsuitable 
> with other functionals ?
> I assume DZVP-GTH basis has a double-zeta valence shell + polarizations ? 
> Does it also exist with diffusion functions (let's say I need density a 
> little further away - an anion, a complex, etc.) ? How good is it compared 
> to TZVP (all-electron) or def2-TZVP ? Or compared to 6-31g* or cc-pVDZ ? 
> Which basis sets for CP2K would be like 6-31g*, TZVP, def2-TZVP and cc-pVDZ 
> ... and why not cc-pVTZ for each of the following QS METHODs: DFTB, GAPW, 
> Which CP2K basis sets have diffusion shells ?
> !> I cannot deduce the shells of basis sets by reading the basis set 
> files, so is there a way to actually see how many s, p, d and/or f shells 
> does a CP2K basis set have ? I can guess whether there are polarizations or 
> not based on the element and type of shells, but I cannot guess the same 
> for diffusion orbitals, as they are of the same type as the covalent shell 
> orbitals.
> !> What QS METHOD is good for organics and not just for semiconductors or 
> metals ? Which are faster and which are slower ? Which BASIS_SET and/or 
> POTENTIAL should I use for good / scientific / publication quality 
> calculations ?
> Can I use one QS METHOD for a central molecule and another QS METHOD and 
> BASIS_SET for surrounding solvent molecules, without QM/MM ? Or one qs 
> method and basis for a central molecule and another method + basis 
> combination for a surface (graphene or semi-conductor or metal) ?
> Is it a good idea to calculate molecular crystals with qs method + basis 
> different from those for single molecules / complexes.
> The way I understand it, plane wave basis sets may not be the best for 
> organics ?
> !> What type of dispersion is most appropriate for organic molecules / 
> organo-metallic complexes, with or without a solvent. And for molecular 
> crystals ?
> !> I see that there are some new DFT types in CP2K, beyond the kind of DFT 
> that Gaussian does. Should I pick any of them and for which kind of systems 
> ?
> Best Regards,
> Dobromir

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