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sanya
sanya@photonics.ru

See $FORCE group of the manual:
TEMP = an array of up to ten temperatures at which the thermochemistry should be printed out. The default is a single temperature, 298.15 K. To use absolute zero, input 0.001 degrees.

>...base from my related review, the functional B3LYP was derived from a uniform electron gas phase... i think its the LDA part...

All the thermochemistry is performed for the gas phase in the ideal gas--harmonic oscillator--rigid rotor approximation. No matter what type of quantum chemistry is used. Therefore, you cannot directly compare your calculated thermochemical data with the experiments, unless the experimental data are for the gas phase, too. However, you can extrapolate the experimental values to the temperature and pressure corresponding to your calculation (temperature given by TEMP parameters in the $FORCE group and zero pressure) for comparison. But remember that it is only an extrapolation, not exact values! On the other hand, you cannot always extrapolate your calculated thermochemical data to the experimental conditions, because there can be phase transitions with their corresponding heats that cannot be guessed from the first principles without special investigation.

See example on Wikipedia: http://en.wikipedia.org/wiki/Heat_of_formation

[ This message was edited on Tue Nov 3 '09 at 1:39pm by the author ]