Solntsev Pasha
solntsev@univ.kiev.ua
>Please, I am trying to get the total energy, enthalpy, gibbs free energy of my system. I compute the thermochemical properties of simple molecule "H2O" but I am confused because I obtained two thermochemical output as follows:
> THERMOCHEMISTRY AT T= 298.15 K
> -------------------------------
> USING IDEAL GAS, RIGID ROTOR, HARMONIC NORMAL MODE APPROXIMATIONS.
> P= 1.01325E+05 PASCAL.
> ALL FREQUENCIES ARE SCALED BY 1.00000
> THE MOMENTS OF INERTIA ARE (IN AMU*BOHR**2)
> 2.07890 4.38535 6.46425
> THE ROTATIONAL SYMMETRY NUMBER IS 1.0
> THE ROTATIONAL CONSTANTS ARE (IN GHZ)
> 867.32830 411.16213 278.93251
> THE HARMONIC ZERO POINT ENERGY IS (SCALED BY 1.000)
> 0.021773 HARTREE/MOLECULE 4778.512983 CM**-1/MOLECULE
> 13.662468 KCAL/MOL 57.163766 KJ/MOL
> Q LN Q
> ELEC. 1.00000E+00 0.000000
> TRANS. 3.00431E+06 14.915558
> ROT. 8.68998E+01 4.464756
> VIB. 1.00017E+00 0.000170
> TOT. 2.61118E+08 19.380484
> E H G CV CP S
> KJ/MOL KJ/MOL KJ/MOL J/MOL-K J/MOL-K J/MOL-K
> ELEC. 0.000 0.000 0.000 0.000 0.000 0.000
> TRANS. 3.718 6.197 -36.975 12.472 20.786 144.800
> ROT. 3.718 3.718 -11.068 12.472 12.472 49.593
> VIB. 57.167 57.167 57.163 0.106 0.106 0.014
> TOTAL 64.604 67.083 9.121 25.050 33.364 194.407
> E H G CV CP S
> KCAL/MOL KCAL/MOL KCAL/MOL CAL/MOL-K CAL/MOL-K CAL/MOL-K
> ELEC. 0.000 0.000 0.000 0.000 0.000 0.000
> TRANS. 0.889 1.481 -8.837 2.981 4.968 34.608
> ROT. 0.889 0.889 -2.645 2.981 2.981 11.853
> VIB. 13.663 13.663 13.662 0.025 0.025 0.003
> TOTAL 15.441 16.033 2.180 5.987 7.974 46.464
> ......END OF NORMAL COORDINATE ANALYSIS......
>How do I get the total E, H, G ? I suppose the E should be the FINAL ENERGY which is -75.5859597519 in the output file. What does "Q" and "LN Q" stands for ?
Q is partition function. You can read any textbook about statistical thermodynamic or, for example, check this link: http://www.gaussian.com/g_whitepap/thermo.htm
Pavel.
>Thanks.