CCL: Help on H.O.F. from MOPAC
- From: "Lukman Olawale Olasunkanmi"
- Subject: CCL: Help on H.O.F. from MOPAC
- Date: Tue, 8 Mar 2011 04:34:42 -0500
Sent to CCL by: "Lukman Olawale Olasunkanmi"
Please, what can you say about the reliability of the Heat of Formation (H.O.F)
data obtained from MOPAC2009? It seems the values are not well comparable to
experimental standard heat of formation values as do S, H and Cp.
I also came across a statement: " A new quantity is the heat of formation
at the defined T. This is intended for use in calculating heats of reaction.
Because of a limitation in the data available, the H.O.F. at T kelvin is defined
as "the heat of formation of the compound at T kelvin from its elements in
their standard state at 298K". Obviously this definition of H.O.F. is
incorrect, but should be useful in calculating heats of reaction, where the
elements in their standard states at 298K drop out". Does this statement
simply mean that the H.O.F obtained in MOPAC is not quantitatively reliable?
Although, I always draw correct qualitative conclusions from the results.
More so, any time I specify the keyword THERMO in my calculations, I obtain this
warning: "the Gradient is too large for force calculation...", do you
think using LET GNORM = 0.01 can solve this problem?
Thank you in anticipation of your swift response.