quadrupole moment not traceless ?

[Axel]

On Jun 20, 1:04 am, Hanning Chen <chenh... at gmail.com> wrote:
> Dear CP2k users,
>
>   I ran a simple SCF calculation on CO2 and found that its output quadrupole
> moment (as shown below) apparently does not satisfy the requirement of
> traceless, i.e., Q(XX)+Q(YY)+Q(ZZ)==0.

>   Does CP2k have its own definition of quadrupole moment rather than the
> standard one?

there is not one but two "standard" definitions.
a quick search on google reveals this page, for example:

http://cccbdb.nist.gov/quadrupole.asp

axel.

>   Thanks.
>
> Hanning Chen
> Ph.D.
> Department of Chemistry
> Northwestern University
> Evasnton, IL 60201
>
> OUTPUT_FILE:
>
>  Reference Point [Bohr]             9.44863138      9.44863173
> 9.44499632
>   Charges
>     Electronic=      -16.0000      Core=      16.0000      Total=
> 0.0000
>   Dipoles are based on the traditional operator.
>   Dipole moment [Debye]
>     X=          0.000478093061    Y=         -0.000005701601    Z=
> 0.005608188292                   Total=            0.005628532793
>   Quadrupole moment [Debye*Angstrom]
>                 XX=        -18.812852208659         XY=
> -0.089714841097         XZ=         -0.083871152755
>                 YY=        -14.716948452691         YZ=
> -0.002201287063         ZZ=        -14.716586168813
>
> INPUT_FILE:
>
> &FORCE_EVAL
>   METHOD Quickstep
>   &DFT
>     &MGRID
>       CUTOFF 300
>     &END MGRID
>     &QS
>       EPS_DEFAULT 1.0E-12
>     &END QS
>     &SCF
>       SCF_GUESS RESTART
>       EPS_SCF 1.0E-10
>       MAX_SCF 1000
>       &OT
>        MINIMIZER DIIS
>        PRECONDITIONER FULL_KINETIC
>       &END OT
>     &END SCF
>     &XC
>       &XC_FUNCTIONAL PBE
>       &END XC_FUNCTIONAL
>     &END XC
>     &POISSON
>      POISSON_SOLVER WAVELET
>      PERIODIC NONE
>     &END POISSON
>     &PRINT
>      &MOMENTS
>       FILENAME =dipole
>       REFERENCE COM
>       PERIODIC = F
>       MAX_MOMENT 2
>      &END MOMENTS
>     &END PRINT
>   &END DFT
>   &SUBSYS
>     &CELL
>       ABC 10.0 10.0 10.0
>       PERIODIC NONE
>     &END CELL
>     &COORD
>   C         5.0000000838        5.0000000000        4.9999999999
>   O         3.8098548376        4.9999999994        4.9999999994
>   O         6.1901450757        5.0000000006        5.0000000006
>     &END COORD
>     &KIND C
>       BASIS_SET DZVP-GTH-PBE
>       POTENTIAL GTH-PBE-q4
>     &END KIND
>     &KIND O
>       BASIS_SET DZVP-GTH-PBE
>       POTENTIAL GTH-PBE-q6
>     &END KIND
>   &END SUBSYS
> &END FORCE_EVAL
> &GLOBAL
>   PROJECT CO2
>   RUN_TYPE ENERGY
>   PRINT_LEVEL MEDIUM
> &END GLOBAL