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Table of Contents
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. Note that the file contains explicit basis sets and potential for all-electron calculations. An explanation of the basis set formats is given here: Basis Sets
- CH4.inp
&GLOBAL PROJECT CH4 RUN_TYPE ENERGY PRINT_LEVEL MEDIUM &END GLOBAL &FORCE_EVAL METHOD Quickstep ! Electronic structure method (DFT,...) &DFT &POISSON ! Solver requested for non periodic calculations PERIODIC NONE PSOLVER WAVELET ! Type of solver &END POISSON &QS ! Parameters needed to set up the Quickstep framework METHOD GAPW ! Method: gaussian and augmented plane waves &END QS &XC ! Parametes needed to compute the electronic exchange potential &XC_FUNCTIONAL NONE ! No xc functional &END XC_FUNCTIONAL &HF ! Hartree Fock exchange. In this case is 100% (no fraction specified). &SCREENING ! Screening of the electronic repulsion up to the given threshold. EPS_SCHWARZ 1.0E-10 ! Threshold specification &END SCREENING &END HF &END XC &END DFT &SUBSYS &CELL ABC 10 10 10 PERIODIC NONE ! Non periodic calculations. That's why the POISSON scetion is needed &END CELL &TOPOLOGY ! Section used to center the atomic coordinates in the given box. Useful for big molecules &CENTER_COORDINATES &END &END &COORD C 4.6470817907 5.0564551166 5.2030612698 H 5.7285481608 5.0545340413 5.2150365876 H 4.2810776129 5.8762854944 5.8061577262 H 4.2804181558 4.1216454580 5.6048052221 H 4.2983162673 5.1733905029 4.1860324290 &END COORD &KIND H !Potential and basis sets for H &BASIS 3 1 0 0 3 1 12.25200000 0.02282200 1.86870000 0.15564000 0.41821000 0.48898000 1 0 0 1 1 0.10610000 1.00000000 1 1 1 1 1 1.00000000 1.00000000 &END POTENTIAL ALL &POTENTIAL 1 0 0 0.20 0 &END &END KIND &KIND C !Potential and basis sets for C &BASIS 5 1 0 0 6 2 1252.60000000 0.00557360 0.00000000 188.57000000 0.04149600 -0.00027440 42.83900000 0.18263000 -0.00255830 11.81800000 0.46129000 -0.03337500 3.55670000 0.44931000 -0.08730500 0.54258000 0.00000000 0.53415000 1 0 0 1 1 0.16058000 1.00000000 1 1 1 3 1 9.14260000 0.04449900 1.92980000 0.23108000 0.52522000 0.51227000 1 1 1 1 1 0.13608000 1.00000000 1 2 2 1 1 0.80000000 1.00000000 &END POTENTIAL ALL &POTENTIAL 4 2 0 0.34883045 0 &END &END KIND &END SUBSYS &END FORCE_EVAL
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
For O2 triplet, the LSD and MULTIPLICITY keywords are needed in the DFT section:
METHOD Quickstep
&DFT
LSD ! Requests a spin-polarized calculation for unpaired electrons
MULTIPLICITY 3 ! Multiplicity = 2S+1 (S= total spin momentum)
...
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 pc-1
5
1 0 0 6 2
2306.70000000 0.00539400 0.00000000
347.15000000 0.04024800 -0.00031692
78.89000000 0.17921000 -0.00259440
21.87600000 0.45978000 -0.03624100
6.66460000 0.45234000 -0.08779000
1.06690000 0.00000000 0.53320000
1 0 0 1 1
0.30700000 1.00000000
1 1 1 3 1
17.02200000 0.04891900
3.68380000 0.24962000
0.99234000 0.51347000
1 1 1 1 1
0.24487000 1.00000000
1 2 2 1 1
1.00000000 1.00000000
- O potential
#O ALLELECTRON ALL
4 4 0
0.24762086 0
- O2 coordinates
O 4.4705353672 4.7577727756 4.9999951398 O 5.5294646329 5.2422272244 5.0000048599
- CO2 coordinates
- H2O coordinates