Author Topic: Different results between t2x and t2x -c  (Read 522 times)

rkloditz

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Different results between t2x and t2x -c
« on: September 26, 2020, 03:22:49 PM »
Hey guys!

I came upon a puzzling "feature" of the t2x script. See below my results of t2x -c and the last entry of t2x:

t2x:

6
Energy =    -475.2662961282
F    1.3809469   -1.0945653   -0.0000000  0.00   -0.0011503    0.0012745    0.0000000
C    0.6600148    0.0000000    0.0000000  0.00    0.0018920    0.0000000   -0.0000001
F    1.3809469    1.0945653   -0.0000000  0.00   -0.0011503   -0.0012745    0.0000000
C   -0.6600148   -0.0000000   -0.0000000  0.00   -0.0018920    0.0000000    0.0000001
F   -1.3809469   -1.0945653    0.0000000  0.00    0.0011503    0.0012745   -0.0000000
F   -1.3809469    1.0945653    0.0000000  0.00    0.0011503   -0.0012745   -0.0000000

t2x -c:

6
Energy = -475.2662962055
F     1.3808817   -1.0945270    0.0000000
C     0.6600139    0.0000000   -0.0000000
F     1.3808817    1.0945270    0.0000000
C    -0.6600139   -0.0000000    0.0000000
F    -1.3808817   -1.0945270   -0.0000000
F    -1.3808817    1.0945270    0.0000000

You will see differences in the coordinates and the energies. These are quite small and especially for the coordinates presumably negligible. But my questions are: Where does this difference come from and which results are the "more right" ones? I might add, that I use turbomole version 7.1. I very much thank you in advance!

Best regards
Roger

Arnim

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Re: Different results between t2x and t2x -c
« Reply #1 on: October 01, 2020, 03:27:50 PM »
Hello Roger,

in short: 't2x' converts the coordinates from the gradient file, 't2x -c' the coordinates from the coord file.

The reason that this differs is because the optimiser (statpt by default) checks whether the convergence criteria are meet and then writes out one last geometry. In order to have orbitals that match these coordinates, one last SCF run is done.

If you run 'sdg energy' and 'grep cy gradient', you will notice that there is one last energy for which is no gradient. This is the energy that belongs to the coordinates in the coord file.

If you need the most right energy (say for a reaction calculation), use the one from 't2x -c'.

I hope that clear this up.

Arnim

rkloditz

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Re: Different results between t2x and t2x -c
« Reply #2 on: October 09, 2020, 11:05:06 AM »
Hi Arnim,