PC GAMESS-related discussion club

Getting the same answer from US and PC_GAMESS DFT optimisations

Richard
bonarlaw@liv.ac.uk

I want to run a dft geometry optimisation of a smallish organometallic with gamess-us (Apr 11, 2008) so that I get the same answer as using pc-gamess. Setting NRAD=63 in gamess-us, with all other parameters in both programs default (input files identical), I get a difference of ca. 0.01 angs in an interesting bond length, which is a bit worrying.

I realize there are many things to consider here, but does anyone have suggestions for settings in gamess-us which are most likely to be responsible for the discrepancy. Or is it in general possible to do this sort of comparison with different dft codes?

BTW, I'm not interested in timings - I know the answer to that - I just want to end up with optimised structures which are to all intents and purposes the same (I'd be happy with 0.001 angs difference).

Richard  



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