PC GAMESS-related discussion club

Tae-Yun Park
taeyun0000@gmail.com

While I¡¯ve been enjoying the performance of PCGAMESS recently, I found another factor that the performance of PCGAMESS could possibly be compared unfairly if one just uses default settings for geometry optimization. The default settings in PCGAMESS are,
OPTTOL = 0.00010
RMS Force = OPTTOL/3 = 0.00003333¡¦
RMAX = 0.1
RMIN = 0.0015

In the case of G03, the default settings are,
Max. Force = 0.00045
RMS Force = 0.00030
Max. Displacement = 0.00180
RMS Displacement = 0.00120

If OPTTOL and Max. Force have got the same meaning, it looks to me that PCGAMESS settings are more severe, which may result in more iterations and calculation time but more accurate geometry. Same for the case of RMS Force setting. I wonder if this is a correct view.

If indeed the default settings are not really equivalent, I wonder if the PCGAMESS¡¯ OPTTOL can be set to 0.00045 to make the similar conditions compared to the case of G03. This makes PCGAMESS¡¯ RMS Force = OPTTOL/3 = 0.00015, which is still smaller than G03. If it is so, what about the RMAX and RMIN? What values could to be used to have the similar conditions to G03 default settings?

Finally, if indeed the PCGAMESS default settings are more sever compared to those of G03, is there any specific reason for that?

Any comments would be highly appreciated.

Many thanks,

Tae-Yun