I am trying to run a single point g09 calculation for a pentagonal planar molecule with D5h symmetry using the B3LYP/LANL2DZ level or theory.

I would like the calculation to use symmetry, however the program that I use to analyze the output file requires the calculation to run with the “NoSymm” keyword to prevent reorganization of the atoms into standard orientation.

At the moment, the input orientation is in the xy plane with the first terminal atom directly on the y-axis. The 5 terminal atoms are then ordered 1-5 in a clockwise rotation.

How can I set the input geometry such that it is already in standard orientation?

I have tried using the “SaveOrientation” keyword which is supposed to “mark the standard orientation as the input orientation” (Gaussian website), however to no avail.

Any help is greatly appreciated! Thank you.

  • $\begingroup$ You can perform two separate calculations, one with symmetry and the other one with nosymm. As long as the electronic energies of these two jobs are equal, you can think they are equivalent. The first job satisfy your needs, and the 2nd job can be used to analyze the output. Is this OK? $\endgroup$
    – jxzou
    Aug 7 at 6:17
  • $\begingroup$ I am trying to compare the linear coefficients in an MO generated from a qualitative calculation using group theory to the quantitative calculation using g09. The program I use (AOMix) gives me the linear coefficients from the g09 calculation, so preferably I’d like the calculation to run with symmetry so that the coefficients are calculated with respect to symmetry. The AOMix program supports symmetry as long as the atoms are already in their standard orientation. $\endgroup$ Aug 7 at 15:18
  • $\begingroup$ What do you mean by 'linear coefficients'? If you mean MO coefficients, you can find them from Gaussian .fch file, or .log file. In such case, there is no need to use AOMix. The MO coefficients are always stored in .fch file. If you also want to find them in .log file, you need to write the keyword pop=full in .gjf. Or maybe you mean the linear combination coefficients of symmetry-adapted basis functions? $\endgroup$
    – jxzou
    Aug 8 at 1:25


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