Author Topic: geometry optimization with 2 dihedrals constrain  (Read 7091 times)


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geometry optimization with 2 dihedrals constrain
« on: October 27, 2020, 04:53:13 PM »
Hi all,
I would like to optimize structure in which 2 dihedrals fixed in their initial values. I have modified coord as follow:
# definitions of internal coordinates
   769 f  1.0000000000000 tors  162  165  167  188 val= 166.85063
   770 f  1.0000000000000 tors  165  167  188  191 val= 246.53136
Also these lines are added into control file:

tors C162  C165  O167  P188 start=166.85063 end=166.85063 stepsize=0.0
tors C165  O167  P188  O191 start=246.53136 end=246.53136 stepsize=0.0

I am using TURBOMOLE V6.4 and got this error after first cycle of optimization. The output in GEO_OPT_FAILED file says:
ERROR in statpt step
  Please look at the output file statpt.tmpout
statpt (blackbox) : TURBOMOLE V6.4 21
 Copyright (C) 2012 TURBOMOLE GmbH, Karlsruhe
    2020-10-23 15:30:43.155
                           this is S T A T P T   
                     hessian and coordinate update for
                          stationary point search
                     by barbara unterreiner, marek sierka,
                           and reinhart ahlrichs
                          quantum chemistry group
                          universitaet  karlsruhe
  Keyword $statpt not found - using default options
        ***************  Stationary point options ******************
           Maximum allowed trust radius:           3.000000E-01
           Minimum allowed trust radius:           1.000000E-03
           Initial trust radius:                   1.500000E-01
           GDIIS used if gradient norm <           1.000000E-02
           Number of previous steps for GDIIS:       5
           Hessian update method:                  BFGS
                        *** Convergence criteria ***               
           Threshold for energy change:            1.000000E-06
           Threshold for max displacement element: 1.000000E-03
           Threshold for max gradient element :    1.000000E-03
           Threshold for RMS of displacement:      5.000000E-04
           Threshold for RMS of gradient:          5.000000E-04
     Number of symmetry restricted degrees of freedom:   774
     Constituted by:     3 translational degrees of freedom
                         3 rotational degrees of freedom
                     768 internal degrees of freedom

Any help/comment will be appreciated.


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Re: geometry optimization with 2 dihedrals constrain
« Reply #1 on: October 28, 2020, 07:03:50 PM »

I don't really understand the $constraint keyword. That is used by TmoleX or the tool scanprep for PES scans and is not needed for fixed internal coordinates.

However, in such a case I would suggest to fix the atoms at their cartesian position by adding an f behind the element in the coord file and optimize in cartesian coordinates.



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Re: geometry optimization with 2 dihedrals constrain
« Reply #2 on: October 29, 2020, 06:48:38 AM »
Dear Arnim,
Hi and thanks for suggestion. I will test fixing corresponding atoms in coord file.