erroneous dipole moments from mp2 calculations

[sampsa]

Dear Forum,

When relaxing water monomer and dimer and calculating their dipole moments
(everything done at the MP2 level, using the "cc-pVDZ" basis set for both O and H,
calculated with the ricc2 module), the ricc2 program reports the following values:

dipole moment for water monomer: >= 2.0 debye
dipole moment for water dimer: >= 3.0 debye

this is rubbish..  from literature, the correct (close to experiment) values are
~ 1.8D and 2.7D (see for example xantheas,  jcp 102 11 (1995)).

I have tried also with

ricc2 -fanal

having the following lines in the control file:

$anadens
 densityfile

where, as the densityfile, I have tried

mp2-gs1d-ur-1a-000.cao
mp2-gsdn-1a-000-total.cao
gsdens
ddens

the output from ricc2 (in the analysis mode) gives me always, in the case of
water dimer, dipole moments of ~ 3.0 debyes.

Have I completely missuderstood something here..?

Interestingly, those large dipole-moment values resemble the Hartree-Fock values.

It gets even better .. when I generate a file in the gaussian cube format and generate
the dipole moment using the information in that file (with a home-made program), i.e.
the electron density and the ionic positions and charges, I get much more reasonable
dipole moment values.

I attached a .zip file with control (you might want to remove the last, analysis-related lines), coordinates and
basis-set information.

Regards,

Sampsa

[Arnim]

Dear Sampa,

close only counts in horseshoes!
If you check your reference carefully, you will find that Xantheas used the aug-cc-pVDZ basis, not cc-pVDZ.

Cheers,

Arnim

[sampsa]

Hello,

Thanks for the swift reply.

How can I access the augmented basis set..?

-----------------------
ENTER A SET OF ATOMS TO WHICH YOU WANT TO ASSIGN BASIS SETS
 ( ATOMIC SET : all none <index list> <identifier> )
 TO OUTPUT ATOMIC SET SYNTAX ENTER A QUESTION MARK  ?
 E.G.  all dz            (DZ BASIS FOR ALL ATOMS)
       all sto-3g hondo  (SCALED STO-3G)
       1,2,4-6 dzp       (DZP BASIS FOR ATOMS 1,2,4,5,6)
       "c" tz            (TZ BASIS FOR ALL CARBON ATOMS)
 ANY DISPLAY COMMAND  dis  MAY BE ENTERED OR YOU MAY
 HIT >return< TO QUIT (GOING BACK TO MAIN MENU)

all aug-cc-pVDZ

 SUPPLYING BASIS SETS TO    6 ATOMS

  THERE ARE NO DATA SETS CATALOGUED IN FILE
 basis
  CORRESPONDING TO NICKNAME o aug-cc-pVDZ                                                           

  IF YOU WANT, I SKIP TO THE LIBRARY /v/linux26_x86_64/appl/chem/TM6.3p/TURBOMOLE/basen/
  DEFAULT(y)

----------------

[Arnim]

Did you consider pressing the return key as define suggests??

[Ian K]

Yeah, what that message is saying is that there isn't an oxygen aug-cc-pVDZ basis set in the 'basis' file in the current directory. The file suggested to check next in the next line is the general basis library.

[sampsa]

Hello again,

I have continued my scientific efforts to get the water mono- and dimer dipole moments right with turbomole (how difficult can that be..?)

Thank you for indicating me to press the enter key ..

.. I did just that and obtained the turbomole "default" basis set.  With that one I get:

monomer: 2.25 debye
dimer       : 2.75 debye

I am happy with the dimer value, but the monomer value isn't even "horseshoes" close.  A beginner in QC as myself would
expect that turbomole with the "standard" basis set would give a correct value for the water monomer dipole moment..!

Something I have missed?  Which key should I press next (the panic button maybe) ?

[Arnim]

Well ... There are different basis set demands for different methods and different properties.
For MP2 calculations larger basis set are needed than for DFT calculations. And to get converged results for dipole moments, diffuse basis functions are needed.

Maybe you could press the TmoleX button? For a beginner it might be easier to start with the GUI. Not all functionalities are covered here, but you won't get lost in define sub-menus.

Cheers,

Arnim

[sampsa]

Hello,

And thanks for the tip again.

I have everything "automatized" here (I have created an ASE interface for turbomole) so I' d like to avoid
the TmoleX button.

Instead, could you please give me an idea of a suitable - diffuse enough - basis set?

As I mentioned before, aug-cc-pVDZ is not available, at least not in the turbomole package I have.

Regards,

Sampsa

[Arnim]

It is available. Please, check again.