high binding energy

[Sandeep Kumar Reddy]

Hi,
    Towards solving this, I have done binding energy calculations for
molecular systems (where they interact through hydrogen bonds) and this
value matches with MP2 results.

It looks like the problem comes in for ionic systems. Did i missed any
keyword in my input file ?

Hope this helps somebody to comment on my input file ...

Thanks & Regards,
Sandeep



On Mon, Jul 2, 2012 at 6:31 PM, Sandeep Kumar Reddy <kuma... at gmail.com>wrote:

> Dear all,
>              I want to calculate binding energy and compare with
> Gaussian's result and then i would like to proceed to bulk simulations.
>
> My system one ion pair (it's an ionic liquid). I did geometry
> optimizations of cation, anion and ion-pair and calculated the binding
> energy. This value is equal to  *-119* *kcal/mol*. After adding BSSE
> corrections, it is reduced to *-116* kcal/mol. For comparison, i carried
> out same calculations at MP2/aug-cc-pVDZ level using Gaussian package and
> this value is equal to -104 kcal/mol (BSSE corrected). A difference of 10
> kcal/mol of such calculation is discouraging.
>
> (I have used same functional, cell parameters, cutoff, potentials for all
> three calculations)
>
>
> I repeated the calculations by changing cutoff (to 480 Ry) and increasing
> box length (20 \AA). But it gives me same binding energy. Additionally, i
> have done same calculations in plane wave basis set using CPMD code. It
> gives 105 kcal/mol, very close to MP2 result.
>
> I am not able to figure out why it happens.  Could anybody comment on my
> input files ?
>
>
> *Ion-pair :*
>
> &GLOBAL
>   PROJECT dimethyl_ammonium_bromide
>   RUN_TYPE GEO_OPT
>   PRINT_LEVEL MEDIUM
> &END GLOBAL
>
> &FORCE_EVAL
>   METHOD Quickstep
>   &DFT
>     BASIS_SET_FILE_NAME  /panfs/home/Xsreddy/cp2k/tests/QS/BASIS_MOLOPT
>     POTENTIAL_FILE_NAME  /panfs/home/Xsreddy/cp2k/tests/QS/POTENTIAL
>     &MGRID
>       CUTOFF 280
>       NGRIDS 5
>     &END MGRID
>     &QS
>       METHOD       GPW
>       EPS_DEFAULT  1.0E-10
>     &END QS
>     &SCF
>       MAX_SCF   50
>       EPS_SCF   1.0E-6
>       SCF_GUESS ATOMIC
>       &OT ON
>         MINIMIZER       CG
>         PRECONDITIONER  FULL_ALL
>         ENERGY_GAP      0.001
>       &END OT
>       &OUTER_SCF
>         MAX_SCF  100
>         EPS_SCF  1.0E-6
>       &END OUTER_SCF
>     &END SCF
>     &XC
>       &XC_FUNCTIONAL  BLYP
>       &END XC_FUNCTIONAL
>       &vdW_POTENTIAL
>         DISPERSION_FUNCTIONAL PAIR_POTENTIAL
>         &PAIR_POTENTIAL
>           TYPE DFTD2
>           REFERENCE_FUNCTIONAL BLYP
>         &END PAIR_POTENTIAL
>       &END vdW_POTENTIAL
>     &END XC
>     &POISSON
>      POISSON_SOLVER WAVELET
>      PERIODIC NONE
>     &END POISSON
>   &END DFT
>   &SUBSYS
>     &CELL
>       ABC 20.0 20.0 20.0
>       PERIODIC NONE
>     &END CELL
>     &COORD
>     H       1.82622900    0.00011700    1.45609900
>     H       0.41368700   -0.00011700    0.43855600
>     N       1.53927100    0.00002300    0.47861600
>     C       1.97625500   -1.24136700   -0.20041700
>     H       3.06445100   -1.28419200   -0.25417500
>     H       1.58040100   -2.09266400    0.34985900
>     H       1.53907000   -1.23367800   -1.19754500
>     C       1.97589400    1.24149000   -0.20039300
>     H       1.54099200    1.23242900   -1.19850300
>     H       1.57755100    2.09264100    0.34831700
>     H       3.06414500    1.28582600   -0.25177600
>     Br     -1.40269500   -0.00003600   -0.01818000
>     &END COORD
>     &TOPOLOGY
>       &CENTER_COORDINATES
>       &END
>     &END
>     &KIND H
>       BASIS_SET  DZVP-MOLOPT-GTH
>       POTENTIAL  GTH-BLYP-q1
>     &END KIND
>     &KIND C
>       BASIS_SET  DZVP-MOLOPT-GTH
>       POTENTIAL  GTH-BLYP-q4
>     &END KIND
>     &KIND N
>       BASIS_SET  DZVP-MOLOPT-GTH
>       POTENTIAL  GTH-BLYP-q5
>     &END KIND
>     &KIND Br
>       BASIS_SET  DZVP-MOLOPT-SR-GTH
>       POTENTIAL  GTH-BLYP-q7
>     &END KIND
>   &END SUBSYS
> &END FORCE_EVAL
> &MOTION
>   &GEO_OPT
>     MAX_FORCE 0.0001
>     MAX_ITER 500
>     OPTIMIZER BFGS
>   &END GEO_OPT
> &END MOTION
>
>
> Other input files are enclosed.
>
> Thanks.
>
> Regards,
> Sandeep
>
>
> *
> *
>
>
>
>
>
>
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