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exercises:2014_ethz_mmm:reaction_energy

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Reaction Energy

In this exercise, you will calculate the reaction energy for the mehane combustion reaction:

Reaction energy:

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.

CH4.inp

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
Starting oordinates for all the moelcules, POTENTIAL and BASIS SET for KIND O are given at the end of the exercise.

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
exercises/2014_ethz_mmm/reaction_energy.1395842952.txt.gz · Last modified: 2020/08/21 10:14 (external edit)