PC GAMESS-related discussion club

Alex Granovsky
gran@classic.chem.msu.su

1. You can try to use $contrl coord=cart
2. Take a look at the excellent PC GAMESS tutorial written by Dr. Kalju Kahn (for link, see the "Tutorial" section of the PC GAMESS homepage),  where you'll find more information on this topic.
3. You can use ChemCraft to symmetrize structures and create list of symmetry-unique atoms for PC GAMESS input.

Best regards,
Alex


On Thu Feb 21 '08, Tae-Yun Park wrote
-------------------------------------
>Recently I found PCGAMESS calculation speed enhances a lot when geometry optimization is performed with symmetry & unique atom information of molecules. For example when the geometry optimization for ethylene is performed with C1 symmetry, i.e.,

>C1
>C      6.0     0.00000   0.00000   0.66790
>H      1.0     0.00000   0.93000   1.22780
>H      1.0     0.00000  -0.93000   1.22780
>C      6.0     0.00000   0.00000  -0.66790
>H      1.0     0.00000  -0.93000  -1.22780
>H      1.0     0.00000   0.93000  -1.22780

>it took about 13.7 sec in our machine, while when D2h is used, i.e.,

>Dnh 2

>C      6.0     0.00000   0.00000   0.66790
>H      1.0     0.00000   0.93000   1.22780

>the calculation was done in 5.4 sec (more than 250% improvement !!).

>Thus, input structure based on symmetry information with unique atoms contributes a lot in terms of calculation speed for geometry optimization.

>I have software that catches the symmetry of a molecule, but it does not generate the PCGAMESS input structure with unique atoms only. I wonder if anyone of you knows or has got any tool to generate such structure information that enhances the speed of geometry optimization with PCGAMESS.

>There might be an input keyword option that PCGAMESS automatically detects this situation, which I¡¯m not aware of yet.

>Any comments related to this subject will highly be appreciated.

>Many thanks in advance,

>Tae-Yun
>