PC GAMESS/Firefly-related discussion club

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Alex Granovsky
gran@classic.chem.msu.su

Indeed, if one performs Hessian calculations,
the thermochemistry data can be found near the
end of the output file. However, one must
take into account that they are computed for the gas
phase at the specified temperature and pressure, and
within ideal gas - harmonic oscillator - rigid rotor
approximation. Another point is that Hessian should
be computed at the global minimum of PES. This means
that one needs to optimize geometry first, and ensure
that there are no imaginary frequencies i.e. that the
structure is the minimum indeed. In more complex cases,
one may need to find several minima to select the proper
(deepest) one. And the things go much worse for non-rigid
molecules with quasi-degenerate minima...

regards,
Alex Granovsky
On Thu Oct 22 '09 8:42pm, Rachel Mae Omongos wrote
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>hello everyone.. my name is Rachel Mae Omongos, a fourth year BS Chemistry student at the MINDANAO STATE UNIVERSITY - ILIGAN INSTITUTE OF TECHNOLOGY here in the PHILIPPINES. I have a subject now, Chem187-Computational Chemistry and our professor gave us a special project and mine was entitled: Heat Capacity and Entropy Calculation from various semiempirical and ab initio methods. Our professor then gave me 5 molecules and one of them was benzene. My question is, can i get those results (the entropy and heat capacity) in the output file without doing any (ballpen and pen) calculations? Are the values of heat capacity and entropy in THERMOCHEMISRTY section in the output file reliable and ready to be reported? please help me with this problem of mine.. thank you so much. more power.