[CP2K:3890] Re: high binding energy

Sandeep Kumar Reddy kuma... at gmail.com
Wed Jul 4 08:50:02 CEST 2012


Dear Matt,
                For Br,  DZVP is the large basis set available in cp2k.
>From last two days, i am continuously running tests on different ion pairs.
All calculations show considerable difference compared to MP2 results.

I will repeat the calculations with extra diffuse functions wherever
possible.

(when i did the calculations on different ion-pairs, i got huge differences
in some cases also ( -40 kcal/mol difference)



Regards,
Sandeep


On Wed, Jul 4, 2012 at 12:06 PM, Matt W <MattWa... at gmail.com> wrote:

> Hi Sandeep,
>
> there is nothing very obviously wrong with your input.
>
> Maybe the basis set is not good enough for the anion? You could see
> whether extra diffuse functions make a big difference...
>
> Matt
>
> On Tuesday, July 3, 2012 11:13:18 AM UTC+1, sandeep wrote:
>>
>> 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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