exercises:2017_ethz_mmm:reaction_energy
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— | exercises:2017_ethz_mmm:reaction_energy [2020/08/21 10:15] (current) – created - external edit 127.0.0.1 | ||
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+ | ====== Reaction Energy ====== | ||
+ | In this exercise, you will calculate the reaction energy for the **methane combustion** reaction: | ||
+ | \[ CH_4 + 2O_2 \rightarrow CO_2 + 2H_2O \] | ||
+ | |||
+ | Reaction energy: | ||
+ | \[ \sum E_\text{products} - \sum E_\text{rectants} = \left (2\cdot E_{H_2O} + E_{CO_2} \right) - \left(E_{CH_4} + 2\cdot E_{O_2}\right) \] | ||
+ | |||
+ | |||
+ | Ground state oxygen, O$_2$, is a triplet diradical, a property which can explain why liquid oxygen is paramagnetic and attracted to the poles of a magnet. | ||
+ | {{ o3.png?600 | | ||
+ | }} | ||
+ | |||
+ | For this reason, to get the energy of the O$_2$ molecule, a LSD calculation is required. | ||
+ | |||
+ | ===== 1.Step ===== | ||
+ | |||
+ | Run a single point calculation for CH$_4$, 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|Basis Sets]] | ||
+ | |||
+ | <code - CH4.inp > | ||
+ | &GLOBAL | ||
+ | PROJECT CH4 | ||
+ | RUN_TYPE ENERGY | ||
+ | PRINT_LEVEL MEDIUM | ||
+ | &END GLOBAL | ||
+ | |||
+ | & | ||
+ | METHOD Quickstep | ||
+ | &DFT | ||
+ | & | ||
+ | PERIODIC NONE | ||
+ | PSOLVER | ||
+ | &END POISSON | ||
+ | & | ||
+ | METHOD GAPW ! Method: gaussian and augmented plane waves | ||
+ | &END QS | ||
+ | |||
+ | & | ||
+ | & | ||
+ | &END XC_FUNCTIONAL | ||
+ | & | ||
+ | & | ||
+ | EPS_SCHWARZ 1.0E-10 | ||
+ | &END SCREENING | ||
+ | &END HF | ||
+ | &END XC | ||
+ | &END DFT | ||
+ | |||
+ | &SUBSYS | ||
+ | &CELL | ||
+ | ABC 10 10 10 | ||
+ | PERIODIC NONE ! Non periodic calculations. That's why the POISSON section is needed | ||
+ | &END CELL | ||
+ | & | ||
+ | & | ||
+ | &END | ||
+ | &END | ||
+ | &COORD | ||
+ | C | ||
+ | H | ||
+ | H | ||
+ | H | ||
+ | H | ||
+ | &END COORD | ||
+ | &KIND H ! potential and basis for H | ||
+ | & | ||
+ | 3 | ||
+ | 1 0 0 3 1 | ||
+ | | ||
+ | 1.86870000 | ||
+ | 0.41821000 | ||
+ | 1 0 0 1 1 | ||
+ | 0.10610000 | ||
+ | 1 1 1 1 1 | ||
+ | 1.00000000 | ||
+ | & | ||
+ | POTENTIAL ALL | ||
+ | & | ||
+ | | ||
+ | | ||
+ | & | ||
+ | &END KIND | ||
+ | &KIND C ! potential and basis for C | ||
+ | &BASIS | ||
+ | 5 | ||
+ | 1 0 0 6 2 | ||
+ | | ||
+ | 188.57000000 | ||
+ | | ||
+ | | ||
+ | 3.55670000 | ||
+ | 0.54258000 | ||
+ | 1 0 0 1 1 | ||
+ | 0.16058000 | ||
+ | 1 1 1 3 1 | ||
+ | 9.14260000 | ||
+ | 1.92980000 | ||
+ | 0.52522000 | ||
+ | 1 1 1 1 1 | ||
+ | 0.13608000 | ||
+ | 1 2 2 1 1 | ||
+ | 0.80000000 | ||
+ | &END | ||
+ | POTENTIAL ALL | ||
+ | & | ||
+ | 4 2 0 | ||
+ | 0.34883045 | ||
+ | &END | ||
+ | &END KIND | ||
+ | |||
+ | &END SUBSYS | ||
+ | &END FORCE_EVAL | ||
+ | </ | ||
+ | |||
+ | If the calculation was performed correctly, the total energy of the CH$_4$ molecule is printed in the output file. | ||
+ | |||
+ | < | ||
+ | **** **** ****** | ||
+ | ***** ** *** *** ** | ||
+ | | ||
+ | ***** ** ** ** ** | ||
+ | **** ** ******* | ||
+ | |||
+ | ..... | ||
+ | |||
+ | ENERGY| Total FORCE_EVAL ( QS ) energy (a.u.): | ||
+ | |||
+ | ..... | ||
+ | |||
+ | **** **** ****** | ||
+ | ***** ** *** *** ** | ||
+ | | ||
+ | ***** ** ** ** ** | ||
+ | **** ** ******* | ||
+ | </ | ||
+ | |||
+ | |||
+ | ===== 2.Step ===== | ||
+ | |||
+ | Modify the input in order to perform the same calculation for: | ||
+ | * H$_2$O | ||
+ | * CO$_2$ | ||
+ | * O$_2$ triplet | ||
+ | |||
+ | <note tip> Atomic coordinates for all the molecules, POTENTIAL and BASIS SET for KIND O are given at the end of the exercise. </ | ||
+ | <note important> | ||
+ | | ||
+ | |||
+ | For O2 triplet, the LSD and MULTIPLICITY keywords are needed in the DFT section: | ||
+ | |||
+ | < | ||
+ | METHOD Quickstep | ||
+ | & | ||
+ | | ||
+ | | ||
+ | ... | ||
+ | </ | ||
+ | |||
+ | Another example can be found here [[basis_sets|Basis Sets]] | ||
+ | |||
+ | ===== 3.Step ===== | ||
+ | At the end, you should get a table like: | ||
+ | |||
+ | ^ Species ^ Total Energy ^ | ||
+ | | CH$_4$ | ||
+ | | O$_2$ | ... | | ||
+ | | H$_2$O | ||
+ | | CO$_2$ | ||
+ | |||
+ | Now you can compute the overall reaction energy. | ||
+ | |||
+ | ===== Questions ===== | ||
+ | - What are the total energies of O$_2$, H$_2$O, CO$_2$, and CH$_4$? | ||
+ | - What is the overall reaction energy of the CH$_4$ combustion? | ||
+ | - **(Optional)** What is the total energy difference between the O$_2$ singlet and triplet state? | ||
+ | |||
+ | ===== Appendix ===== | ||
+ | |||
+ | ==== Basis Set for Oxygen ==== | ||
+ | < | ||
+ | #O pc-1 | ||
+ | 5 | ||
+ | 1 0 0 6 2 | ||
+ | | ||
+ | 347.15000000 | ||
+ | | ||
+ | | ||
+ | 6.66460000 | ||
+ | 1.06690000 | ||
+ | 1 0 0 1 1 | ||
+ | 0.30700000 | ||
+ | 1 1 1 3 1 | ||
+ | | ||
+ | 3.68380000 | ||
+ | 0.99234000 | ||
+ | 1 1 1 1 1 | ||
+ | 0.24487000 | ||
+ | 1 2 2 1 1 | ||
+ | 1.00000000 | ||
+ | </ | ||
+ | |||
+ | ==== Potential for Oxygen ==== | ||
+ | < | ||
+ | #O ALLELECTRON ALL | ||
+ | 4 4 0 | ||
+ | | ||
+ | </ | ||
+ | |||
+ | ==== Coordinates for O$_2$ ==== | ||
+ | < | ||
+ | O | ||
+ | O | ||
+ | </ | ||
+ | |||
+ | ==== Coordinates for CO$_2$ ==== | ||
+ | < | ||
+ | C | ||
+ | O | ||
+ | O | ||
+ | </ | ||
+ | |||
+ | ==== Coordinates for H$_2$O ==== | ||
+ | < | ||
+ | O | ||
+ | H | ||
+ | H | ||
+ | </ | ||
exercises/2017_ethz_mmm/reaction_energy.txt · Last modified: 2020/08/21 10:15 by 127.0.0.1