[CP2K:2440] TPSS - differences with cp2k/gamess

[Teodoro Laino]

Dear Inga,

> The experimental values are: CC bond length - 1.2027 A; CH bond length
> - 1.062 A.
>
> With gamess-us (TPSS/TZ2P), I obtain r(CC) = 1.2028 A, r(CH) = 1.0648
> A, corresponding to a mean relative error (MRE) of 0.13%.
>
> With gaussian09 (TPSS/6-311G*), I obtain r(CC) = 1.2049 A, r(CH) =
> 1.0656 A, MRE = 0.26%.
>
> With cp2k (TPSS/GTH-PBE+TZ2P-MOLOPT, version 2.1.79), I obtain r(CC) =
> 1.2101 A, r(CH) = 1.0739 A, MRE = 0.87%
>
> Both, the CC and the CH bond are significantly longer in the cp2k
> optimized geometry compared with the other two geometries.
>   
Significantly longer?!? (we are talking about  errors smaller than 1%).
well.. let's have a look at your input:

0) Pseudo is not tuned for TPSS ! using pseudo tuned for a specific 
functional (PBE in your case) and use another functional for DFT 
calculations is looking for trouble (unless you know what you are doing..).
Comparison is done with all-electron calculations (GAMESS and G03).
Maybe you may want to try all-electron also in cp2k and avoid the 
problem of the PSEUDO.
1) In cp2k you have periodicity (which you don't have for GAMESS or 
G03). This can already account for some devitions.
    Use a decoupler for eliminate this effect (see-> &POISSON and older 
posts). Even using a larger cell you have always interaction at the 
multipolar level (which may be small.. possibly on the same order of the 
error you see for the bonds).
2) EPS_DEFAULT 1.0E-8 : why did you choose this value?! It's a quite 
relaxed one: the default is *1.0E-12 *!!!!
3) same for DENSITY_CUTOFF: again, please use defaults unless you know 
what you are really doing..

Honestly I find it a miracle to have such good agreements with all the 
above observations !
Possibly, fixing the points above you  may get better agreement.

There is always the possibility for a bug or slightly different 
implementation of TPSS: Fawzi that wrote that functional can comment on 
that. The feeling is that if there is a real bug it will be a dirty job 
to find it due to the small differences.

Teo

> For the harmonic frequencies, I obtain deviations from the
> experimental harmonic frequencies of:
> with gamess mean absolute deviation (MAD) =  14 cm-1, RMSD = 17 cm-1
> with gaussian MAD = 13 cm-1, RMSD = 18 cm-1
> with cp2k MAD = 46 cm-1, RMSD = 52 cm-1
>
> For the anharmonic frequencies, I obtain deviations from experimental
> anharmonic frequencies of:
> with gamess MAD = 36 cm-1, RMSD = 41 cm-1
> with cp2k MAD = 52 cm-1, RMSD = 66 cm-1
>
> The disagreement at the harmonic level is much more pronounced than at
> the anharmonic level.
>
> For other functionals, like PBE, the agreement of the results from
> cp2k and other electronic structure programs is very good.
>
> The calculations are performed fully periodic, using a 10x10x14 A^3
> unit cell, which leaves 10 A distance between the repeated C2H2
> molecules. I also tested larger unit cells, but the results do not
> change.
>
> My question is: Am I doing something wrong? Is there something I need
> did not take into account?
> This is the input I used for the optimization (and similar ones for
> the harmonic frequency analysis and PES generation):
>
> &FORCE_EVAL
>   METHOD Quickstep
>   &DFT
>       BASIS_SET_FILE_NAME  /Users/cp2k/BASIS_MOLOPT
>       POTENTIAL_FILE_NAME /Users/cp2k/GTH_POTENTIALS
>     &MGRID
>       CUTOFF 300
>     &END MGRID
>     &QS
>       EPS_DEFAULT 1.0E-8
>     &DISTRIBUTION
>       SKIP_OPTIMIZATION TRUE
>     &END DISTRIBUTION
>     &END QS
>     &SCF
>       EPS_SCF 1.0E-7
>       SCF_GUESS RESTART
>       MAX_SCF 500
>       &OT
>         PRECONDITIONER FULL_ALL
>          MINIMIZER DIIS
>          STEPSIZE 0.08
>          N_DIIS 10
>        &END OT
>        &OUTER_SCF
>          OPTIMIZER DIIS
>          MAX_SCF 30
>        &END OUTER_SCF
>     &END SCF
> &XC
>      DENSITY_CUTOFF 1.0e-9
>      &XC_GRID
>       XC_SMOOTH_RHO SPLINE3
>       XC_DERIV SPLINE3_SMOOTH
>      &END XC_GRID
>      &XC_FUNCTIONAL
>      &TPSS
>      &END TPSS
>      &END XC_FUNCTIONAL
>    &END XC
>   &END DFT
>   &SUBSYS
>     &CELL
>       ABC 10.0 10.0 14.0
>     &END CELL
>     &COORD
>   C         5.0000000000        5.0000000000        6.3854890654
>   C         5.0000000000        5.0000000000        7.5956054689
>   H         5.0000000000        5.0000000000        5.3115675669
>   H         5.0000000000        5.0000000000        8.6694973010
>     &END COORD
>     &KIND C
>       BASIS_SET TZV2P-MOLOPT-GTH
>       POTENTIAL GTH-PBE-q4
>     &END KIND
>     &KIND H
>       BASIS_SET TZV2P-MOLOPT-GTH
>       POTENTIAL GTH-PBE-q1
>     &END KIND
>   &END SUBSYS
> &END FORCE_EVAL
> &GLOBAL
>   PROJECT c2h2_tpss
>   PREFERRED_FFT_LIBRARY FFTSG
>   RUN_TYPE GEO_OPT
>   PRINT_LEVEL LOW
> &END GLOBAL
> &MOTION
>   &GEO_OPT
>     MAX_ITER 300
>     MAX_FORCE 1.E-6
>     OPTIMIZER BFGS
>   &END GEO_OPT
> &END MOTION
>
> I also tried using a higher cutoff and different interpolation
> schemes, but the results did not change.
> I am grateful for any comments.
> Thanks
> Inga
>
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>
>