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Table of Contents
Reaction Energy
In this exercise, you will calculate the reaction energy for the mehane combustion reaction:
Ground state oxygen, O2, is a triplet diradical, a property which can explain why liquid oxygen is paramagnetic and attracted to the poles of a magnet.
For this reason, to get the energy of the O2 molecule, a LSD calculation is required.
1.Step
Run a single point calculation for CH4, using the given input file.
If the calculation was performed correctly, the total energy of the CH4 molecule is printed in the output file.
**** **** ****** ** PROGRAM STARTED AT ***** ** *** *** ** PROGRAM STARTED ON ** **** ****** PROGRAM STARTED BY ***** ** ** ** ** PROGRAM PROCESS ID **** ** ******* ** PROGRAM STARTED IN ..... ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): ..... **** **** ****** ** PROGRAM ENDED AT ***** ** *** *** ** PROGRAM RAN ON ** **** ****** PROGRAM RAN BY ***** ** ** ** ** PROGRAM PROCESS ID **** ** ******* ** PROGRAM STOPPED IN
2.Step
Modify the input in order to perform the same calculation for:
- H2O
- CO2
- O2 TRIPLET
Remember that the O2 ground state is a triplet state, with non paired electrons (MULTIPLICITY = 3). The LSD and MULTIPLICITY keywords are needed in the DFT section:
Another example can be found here Basis Sets
3.Step
At the end, you should get a table like:
Species | Total Energy |
---|---|
CH4 | … |
O2 | … |
H2O | … |
CO2 | … |
Now you can compute the overall reaction energy.
Questions
- Report the total energy for all the molecules, and the overall reaction energy for CH4 combustion.
- (Optional) Compute the total enery for O2 singlet and the energy difference with O2 triplet.
Additional material
- O BASIS SET
- O POTENTIAl
- O2 coordinates
- CO2 coordinates
- CH4 coordinates