[molpro-user] To understand the reason for difference betweeen two outputs for the same situation developed by MOLPRO
Hans-Joachim Werner
werner at theochem.uni-stuttgart.de
Mon Nov 13 11:28:03 CET 2017
As I wrote in my previous mail, the two structures are (within the optimization accuracy) equivalent. By default, Molpro does not orient or shift the molecule if xyz coordinates are given in the input. In a geometry optimization, the final cartesian coordinates therefore depend on the initial ones. You can force orientation and shifting to the center of mass using the "orient,mass“ directive (but this sometimes slows down geometry optimizations and is better done after the optimization). If this is done using your two final structures, one obtains (see attached outputs):
structure from h2cs_opt-fixed-1.out
NR ATOM CHARGE X Y Z
1 H1 1.00 0.000000000 1.765967499 -3.211856242
2 H2 1.00 0.000000000 -1.765967499 -3.211856242
3 C 6.00 0.000000000 0.000000000 -2.101410757
4 S 16.00 0.000000000 0.000000000 0.989231483
structure from H2CS_opt2.out
1 H1 1.00 0.000000000 1.765973450 -3.211867166
2 H2 1.00 0.000000000 -1.765973450 -3.211867166
3 C 6.00 0.000000000 0.000000000 -2.101417486
4 S 16.00 0.000000000 0.000000000 0.989234692
The very minor differences of the structures are due to the optimization accuracy, but the energies are (with the accuracy of convergence) the same
h2co_orient1.out: !CCSD(T) total energy -436.833295371578
h2co_orient2.out: !CCSD(T) total energy -436.833295371017
If you add another atom (e.g. He) to the geometry, the energy and other results will depend only on the 3N-6 internal coordinates of the system,
not on rotations or translations of the entire system.
The accuracy of the geometry optimization can be affected with some options, for example
optg,gradient=1.d-5
would give you more accurate coordinates. But this will have virtually no effect on the results (energies, frequencies, or whatever). And the effect
will also be much smaller than other errors of the calculation, as for example basis set incompleteness errors.
Note that the center of mass also depends on the isomers, see section 10 or the manual. By default, average isotopic masses are used.
Best regards
Joachim
---
Prof. Dr. Hans-Joachim Werner
Institut für Theoretische Chemie
Universität Stuttgart
Pfaffenwaldring 55
70569 Stuttgart, Germany
e-mail: werner at theochem.uni-stuttgart.de
> Am 13.11.2017 um 08:55 schrieb Prof. Suresh Chandra <suresh492000 at yahoo.co.in>:
>
> Dear Prof. Dr. Werner,
>
> Many thanks for your email. Please let me know which coordinates are accurate, as the coordinates of atoms are with respect to the center-of-mass of the molecule.
>
> To my understanding, the molecule is not shifted as such. Since the coordinates of atoms are changed differently, it is something different from the shift of molecule. Please let me know which command in my input file has made this shift. In fact, we want to use the MOLPRO for calculation of interaction potential between the molecule and the interacting particle, say He atom, by putting it at various positions.
>
> Please find attached herewith the two output files for your kind consideration.
>
> With regards,
>
> Prof. Suresh Chandra,
>
> Deputy Director & Professor,
> Amity Centre for Astronomy & Astrophysics,
> Amity Institute of Applied Sciences,
> Amity University, Sector-125,
> NOIDA 201313, U.P., India
>
> Email: schandra2 at amity.edu;
> suresh492000 at yhoo.co.in
>
> Mob. +91-9818005663, 8368908608
> =========================================
> Alexander von Humboldt Fellow (Germany),
> Former Director, School of Physical Sciences,
> S.R.T.M. University, Nanded (Maharashtra)
>
>
> On Monday, 13 November 2017 2:34 AM, Hans-Joachim Werner <werner at theochem.uni-stuttgart.de> wrote:
>
>
> The internal coordinates and also the harmonic frequencies are the same (within the optimization accuracy).
> Only in one case the molecule is shifted along the z-axis, which of course has no effect on the results.
> Best regards
> Joachim Werner
> ---
> Prof. Dr. Hans-Joachim Werner
> Institut für Theoretische Chemie
> Universität Stuttgart
> Pfaffenwaldring 55
> 70569 Stuttgart, Germany
> e-mail: werner at theochem.uni-stuttgart.de
>
>
>
>
> > Am 10.11.2017 um 07:50 schrieb Prof. Suresh Chandra <suresh492000 at yahoo.co.in>:
> >
> > Dear Friends,
> >
> > We have optimized H2CS on 21 September 2017 and on 1 April 2014 with the help of
> > MOLPRO using the same basis-set and the same method, but we got two different results,
> > attached herewith (where lines are deleted in the text; one can ask for complete output). For example,
> > in the output file h2cs_opt-fixed.out, the optimized coordinates are:
> >
> > Atomic Coordinates
> >
> > Nr Atom Charge X Y Z
> >
> > 1 H1 1.00 0.000000000 1.765967499 -2.745177896
> > 2 H2 1.00 0.000000000 -1.765967499 -2.745177896
> > 3 C 6.00 0.000000000 0.000000000 -1.634732411
> > 4 S 16.00 0.000000000 0.000000000 1.455909829
> >
> > On the other side, the optimized coordinates in the output file H2CS_opt2.out are:
> >
> > Atomic Coordinates
> >
> > Nr Atom Charge X Y Z
> >
> > 1 H1 1.00 0.000000000 1.765973450 -3.050725593
> > 2 H2 1.00 0.000000000 -1.765973450 -3.050725593
> > 3 C 6.00 0.000000000 0.000000000 -1.940275913
> > 4 S 16.00 0.000000000 0.000000000 1.150376265
> >
> > There is large difference. Could you please suggest me some reason for the
> > difference between the two outputs.
> >
> > With regards,
> >
> > Prof. Suresh Chandra,
> >
> > Deputy Director & Professor,
> > Amity Centre for Astronomy & Astrophysics,
> > Amity Institute of Applied Sciences,
> > Amity University, Sector-125,
> > NOIDA 201313, U.P., India
> >
> > Email: schandra2 at amity.edu;
> > suresh492000 at yhoo.co.in
> >
> > Mob. +91-9818005663, 8368908608
> > =========================================
> > Alexander von Humboldt Fellow (Germany),
> > Former Director, School of Physical Sciences,
> > S.R.T.M. University, Nanded (Maharashtra)
>
> > <h2cs_opt-fixed_modified.out><H2CS_opt2_modified.out>_______________________________________________
> > Molpro-user mailing list
> > Molpro-user at molpro.net
> > http://www.molpro.net/mailman/listinfo/molpro-user
>
>
>
> <H2CS_opt2.out><h2cs_opt-fixed.out>
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