[CP2K:2971] Re: Lowdin analysis

[Manh-Thuong Nguyen]

Hi Matthias,

Many thanks for your suggestion.
It is really basis set dependent. I've tried again with most basis sets I
have, only the MOLOPT-SR types can give me some "right physics" results.
Btw, could you please tell me some technical papers about this problem?

Thanks again,
Manh


On Sun, Dec 5, 2010 at 3:06 PM, Matthias Krack <matthia... at psi.ch>wrote:

> Hi Manh,
>
> population analyses are known to be very sensible to the basis set
> choice. I guess also in this case the TZV2P MOLOPT basis set is the
> reason for the unexpected result. The MOLOPT basis sets include
> relatively small exponents which might cause linear dependencies in
> the overlap matrix. The Lowdin population analysis requires the
> calculation of S**(1/2) which involves (in CP2K) a diagonalisation of
> the overlap matrix. However, an ill-conditioned overlap matrix will
> most likely result in a weird charge partition. Therefore, I would
> suggest to employ different basis sets, e.g. the MOLOPT-SR or the DZVP/
> TZVP basis sets.
>
> Best,
>
> Matthias
>
> On 3 Dez., 17:46, Manh <manht... at gmail.com> wrote:
> > Hello everyone,
> >
> > I calculate the Mulliken and Lowdin charges for a water molecule. The
> > results are:
> >
> > ----------------------------------------------------------------
> >
> >  MULLIKEN POPULATION ANALYSIS
> >
> >  # Atom  Element  Kind  Atomic population                Net charge
> >       1     H        1           0.780838                  0.219162
> >       2     H        1           0.780981                  0.219019
> >       3     O        2           6.438182                 -0.438182
> >  # Total charge                  8.000000                  0.000000
> >
> >  LOWDIN POPULATION ANALYSIS
> >
> >  # Atom  Element  Kind  Atomic population                Net charge
> >       1     H        1           1.210449                 -0.210449
> >       2     H        1           1.210473                 -0.210473
> >       3     O        2           5.579079                  0.420921
> >  # Total charge                  8.000000                  0.000000
> >
> > --------------------------------------------------------
> >
> > I think that the Lowdin analysis has some problem.
> >
> > Here is my input:
> >
> > ---------------------------------------------
> >
> > &FORCE_EVAL
> >   METHOD Quickstep
> >   &DFT
> >     BASIS_SET_FILE_NAME ../../../BASIS_MOLOPT
> >     POTENTIAL_FILE_NAME ../../../GTH_POTENTIALS
> >     RESTART_FILE_NAME H2O-RESTART.wfn.wfn
> >     &QS
> >       METHOD GPW
> >       EXTRAPOLATION ASPC
> >       EXTRAPOLATION_ORDER 3
> >     &END QS
> >     &MGRID
> >       CUTOFF 400
> >       NGRIDS 5
> >     &END
> >     &SCF
> >       MAX_SCF 20
> >       SCF_GUESS RESTART
> >       EPS_SCF 1.0E-6
> >       &OT
> >         PRECONDITIONER  FULL_SINGLE_INVERSE
> >         MINIMIZER  CG
> >       &END
> >       &OUTER_SCF
> >         MAX_SCF 10
> >         EPS_SCF 1.0E-6
> >       &END
> >       &PRINT
> >         &RESTART
> >           &EACH
> >             QS_SCF 0
> >             GEO_OPT 2
> >           &END
> >           ADD_LAST NUMERIC
> >           FILENAME RESTART.wfn
> >         &END
> >         &RESTART_HISTORY OFF
> >         &END
> >       &END
> >     &END SCF
> >
> >     &XC
> >       &XC_FUNCTIONAL PBE
> >       &END XC_FUNCTIONAL
> >     &END XC
> >
> >     &PRINT
> >      &MULLIKEN
> >      &END MULLIKEN
> >
> >      &LOWDIN
> >      &END LOWDIN
> >     &END
> >
> >   &END DFT
> >   &SUBSYS
> >     &CELL
> >    ABC [angstrom]   30 30 30
> >     &END CELL
> >     &TOPOLOGY
> >       COORD_FILE_NAME water.xyz
> >       COORDINATE xyz
> >     &END
> >
> >     &KIND O
> >       BASIS_SET TZV2P-MOLOPT-GTH
> >       POTENTIAL GTH-PBE-q6
> >     &END KIND
> >     &KIND H
> >       BASIS_SET TZV2P-MOLOPT-GTH
> >       POTENTIAL GTH-PBE-q1
> >     &END KIND
> >
> >   &END SUBSYS
> >
> > &END FORCE_EVAL
> >
> > &GLOBAL
> >   PRINT_LEVEL LOW
> >   PROJECT H2O
> >   RUN_TYPE ENERGY
> >   WALLTIME 285000
> > &END GLOBAL
> >
> > &MOTION
> >     &GEO_OPT
> >      MAX_ITER 5000
> >      MAX_FORCE 0.00010
> >      OPTIMIZER BFGS
> >     &BFGS
> >     &END
> >   &END
> > &END
> >
> > ------------------------------------------------
> >  the water.xyz file is
> > ----------------------------------------
> >        3
> >  water
> >   H         8.4351137971        5.1620318678       12.1510352783
> >   H         8.5534822942        3.6347695084       12.1803075532
> >   O         7.9011326518        4.3528437024       12.1874564118
> > ------------------------------------------------
> >
> > Regards,
> > Manh
>
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