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

[Juerg Hutter]

Hi

in addition to the points mentioned by Teo (I would focus
on EPS_DEFAULT as the main source of errors) there is
the problem with the kinetic energy density in CP2K.
For systems with regions of very small density (e.g. isolated
molecules) we have a problem of numerical stability.
This is usually resulting in slow convergence and can mean
that you get rather large differences to reference data.

best regards

Juerg Hutter

----------------------------------------------------------
Juerg Hutter                   Phone : ++41 44 635 4491
Physical Chemistry Institute   FAX   : ++41 44 635 6838
University of Zurich           E-mail: hut... at pci.uzh.ch
Winterthurerstrasse 190
CH-8057 Zurich, Switzerland
----------------------------------------------------------


On Thu, 3 Dec 2009, ires wrote:

> Dear all,
>
> I did some test calculations on acetylene, using different density
> functional approximations and electronic-structure programs. There I
> noticed that the TPSS results obtained with cp2k are different from
> the ones obtained with gamess or gaussian. This was the case for both
> the geometry and the vibrational frequencies of acetylene:
>
> 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.
>
> 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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