PM6

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Teodoro Laino

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Apr 30, 2008, 11:36:50 AM4/30/08
to cp...@googlegroups.com, Teodoro Laino
Dear All,

good news:
with the today commit, (finally !!), there's the possibility to run
PM6 semi-empirical calculation in
CP2K (fully support for all elements) (at the moment only numerical
derivatives.. analytical will come soon).

bad news:
In the original version of PM6 there are some terms that make the
heat of formation a discontinuous function of
the nuclei positions (are just correction terms, constants that
become zero for different topological configurations) that
we didn't implement. Therefore for few situations there could be
discrepancies between the heat of formation of CP2K
and the one of MOPAC (but the electronic energy should anyway be the
same (within numerical errors (see below)).
An example is H-CC-H, that has a constant correction term to the heat
of formation of the triple bond that becomes
zero when the triple bond is broken (it's just a step function).

Why have been these terms omitted?
Simply because there's no trace of them in the PM6 paper.

I'm sure that there could be other hidden corrections/parameters not
explicitly mentioned in the paper (classical correction
like the one for correcting the sp2 pyramidalization, that we didn't
implement as well), so in case of big discrepancies
compared with MOPAC2007 feel free to post here your input file and a
short description of the problem.

What does it mean big discrepancies?
These are the values for the heat of formation (kcalmol) of the
following systems (CP2K/MOPAC2007)

HCl (17.0356/17.0345)
BrCl (2113.534/2113.493)
TiO (202.714/202.633)

If you have some discrepancy larger than the ones above, check always
the value of the electronic energy that
must anyway be VERY similar (the only difference is in the way we
compute integrals.. so just kind of numerical
errors, totally negligible).
Have fun!!

Teo

Teodoro Laino

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May 1, 2008, 2:55:16 PM5/1/08
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Just for record:

The analytical derivatives for PM6 and other SE methods using d-
orbitals have been implemented and are
available in the CVS.

Cheers,
Teo

B Goldf

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Sep 11, 2019, 4:28:11 AM9/11/19
to cp2k
Dear Teo,

besides PM6, PM6-FM is implemented in CP2K6.1.
Do you know which modification "FM" makes?
Is there some reference for PM6-FM?

Many thank
Bernd

Thomas Kühne

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Sep 11, 2019, 5:26:49 AM9/11/19
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Dear Bernd, 

„FM“ stands for force-matched. It is a PM6 custom parametrization for 
aqueous systems obtained by force matching to MP2 water clusters. 

Cheers, 
Thomas

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==============================
Thomas D. Kühne
Dynamics of Condensed Matter
Chair of Theoretical Chemistry
University of Paderborn
Warburger Str. 100
D-33098 Paderborn
Germany

B Goldf

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Sep 12, 2019, 4:08:34 AM9/12/19
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Dear Thomas,
Vielen Dank !
Grüße Bernd
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B Goldf

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Sep 21, 2019, 9:08:28 AM9/21/19
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Dear Thomas
dear all,

is it possible to run
QM / "QM"
eg. DFT/SE like PBE / PM6
via FORCE_MIXING
in cp2k,rather than QM/"MM"?

Best regards
Bernd

Matt W

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Sep 21, 2019, 9:47:10 AM9/21/19
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Yes, but only in an ONIOMM like subtractive method. You wouldn't be able to electrostatically couple the two representations.

B Goldf

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Sep 22, 2019, 1:48:04 PM9/22/19
to cp2k
Dear Matt,
many thanks!

B Goldf

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Sep 26, 2019, 9:28:38 AM9/26/19
to cp2k
Dear Matt

an example subractive
CP2K QMMM   (2016_summer_school)
scheme is

&MULTIPLE_FORCE_EVALS
  FORCE_EVAL_ORDER 2 3 
&END

&FORCE_EVAL 
 METHOD MIXED
 &MIXED
   MIXING_TYPE GENMIX
   &GENERIC
     MIXING_FUNCTION X+Y-Z
     VARIABLES X Y Z
   &END GENERIC
 &END
&END FORCE_EVAL

&FORCE_EVAL 
  METHOD FIST
&END FORCE_EVAL

&FORCE_EVAL 
  METHOD QS
&END FORCE_EVAL

&FORCE_EVAL 
  METHOD FIST
&END FORCE_EVAL


So the way to set up
a (DFT)PBE-PM6 scheme would be


&MULTIPLE_FORCE_EVALS
  FORCE_EVAL_ORDER 1 2 
&END

&FORCE_EVAL 
  METHOD QS
      PM6
....
&END FORCE_EVAL

&FORCE_EVAL 
  METHOD QS
      PBE
.....
&END FORCE_EVAL


Would this be correct?
Many thanks
Bernd




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