Hi,
In our research group we are frequently using the QM-codes gaussian and turbomole. Some people currently using gaussian, are planning to switch to turbomole (much faster
, however they would like to retain the work they've done with gaussian (i.e. they do not want to redo all the calculations in tm, if possible) meaning that
they would like to be able to compare an absolute energy obtained with gaussian with an absolute energy obtained with tm. From the post on this forum (
http://www.turbo-forum.com/index.php?topic=54.0) I understand that, in principle this should be possible unless using the same functional, basis set, etc.
So, as tm-user I started to do some quick test-calculations for them. I did a single point energy calculation on methane with B3LYP/6-31g*; here are the results:
1) in Gaussian I find an energy of -40.5184205770 hartree
2) in tm I find an energy of -40.51765327052 hartree
this gives a
difference of about 2 kJ/mol between the absolute energies, although I expected to find a much lower value.
Is it possible to comment on this? Is this difference expected or not?
Best regards,
Bart
PS: I've (double) checked that I'm really using the same basis set in both programs, so this can't be the problem. Next to this, I used the
b3-lyp_Gaussian functional in tm and a
m3 gridsize.