quadrupole moment not traceless ?

[Hanning Chen]

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?

  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
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