Hi.
As anticipated in the thread about the PDF manual, I have a problem with the Activity about the energy of cyclohexane derivatives.
The manual reports the following values for the energy after optimization:
Cyclohexane: 30 kJ/mol
Diequatorial: 40 kJ/mol
Diaxial: 98 kJ/mol
I tried to carefukky replicate the configuration, udes MMFF84 as field for optimization and the command Extensions→Calculate→Energy.
I find very different values:
Cyclohexane: 9.91 (I suppose kJ/mol, the units are not indicated)
Diequatorial: 315.93 kJ/mol
Diaxial: 323,78 kJ/mol
I tried several times, trying to avoid mistakes with the positions of the groups, but the results persist.
Probably I am missing something simple, but could you help?
Thanks.
It sounds like you’re using different methods (e.g., UFF and MMFF94) and don’t understand why you get different numbers?
Each force field or method has different mechanisms for calculating energies. For example, UFF does not include electrostatic terms, while MMFF94 does.
So yes, relative energies will be different with different methods. Is that your question?
Hi.
Actually I was trying to replicate the configurations and the energy shown in the Activity. Using Extensions→Calculate→Energy I noticed the Avogadro reports the MMFF94 value, so I used the same field for the optmization. Maybe the values in the manual were obtained with older versions of Avogadro, using different methods?