Lesson 1: Calculate the thermodynamic properties

Objective: Calculate the thermodynamic properties, H, Cp, and S of ethylene as functions of the temperature. Results are presented in the CHEMKIN format for reaction energineering simulations. Input information is taken from a quantum chemistry calculation.

Prerequisite: Thermo calculations require geometries, frequencies, and heat of formation (if CHEMKIN format output is requested) of the molecular species. Geometry and frequencies can be calculated using a quantum chemistry package. For this lesson, we used the Gaussian program, but any other program can also be used. Heat of formation can be obtained from the NIST database.

Procedure

Thermo program can parse both Gaussian output and Fchk files. Here are the two example ouput files for ethylene.

• C2H4.log: Linux Gaussian output file for ethylene.
• C2H4.FChk: Fchk file for ethylene.

Step 1: Open Thermo GUI from JODAF. On the Thermo GUI, click on "File" --> "Open": choose the file C2H4.log

Step 2: Enter the temperature range that you want to calculate.

Step 3: If you want the thermodynamic data in CHEMKIN format, you have the give a Heat of Formation at a temperature. In this case the Heat of Formation of ethylene at 298 K is 52.47 kJ/mol (Source: CHEMKIN Thermodynamic database ).

Step 4: You have to save the thermo input file before submitting it

• C2H4.therm.inp: Thermo input file for ethylene

• C2H4.therm.out: Thermo output file