User Tools

Site Tools


exercises:2014_ethz_mmm:reaction_energy

This is an old revision of the document!


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
  6
  1  0  0  4  1
         75.42300000          0.00240650
         11.35000000          0.01848700
          2.59930000          0.08974200
          0.73513000          0.28111000
  1  0  0  1  1
          0.23167000          1.00000000
  1  0  0  1  1
          0.07414700          1.00000000
  1  1  1  1  1
          1.60000000          1.00000000
  1  1  1  1  1
          0.45000000          1.00000000
  1  2  2  1  1
          1.25000000          1.00000000
      &END
      POTENTIAL ALL
      &POTENTIAL
          1    0    0
          0.20 0
      &END
    &END KIND
    &KIND C                                    !Potential and basis sets for C             
      &BASIS
  9
  1  0  0  8  2
       7857.10000000          0.00056825          0.00000000
       1178.70000000          0.00439150         -0.00000059
        268.32000000          0.02250400         -0.00006275
         75.94800000          0.08665300         -0.00075773
         24.55900000          0.24405000         -0.00733080
          8.62120000          0.44148000         -0.03893200
          3.12780000          0.35332000         -0.08890800
          0.82202000          0.00000000          0.21689000
  1  0  0  1  1
          0.33017000          1.00000000
  1  0  0  1  1
          0.11463000          1.00000000
  1  1  1  4  1
         33.77500000          0.00602940
          7.67660000          0.04322800
          2.23570000          0.16301000
          0.76447000          0.36504000
  1  1  1  1  1
          0.26232000          1.00000000
  1  1  1  1  1
          0.08463800          1.00000000
  1  2  2  1  1
          1.40000000          1.00000000
  1  2  2  1  1
          0.45000000          1.00000000
  1  3  3  1  1
          0.95000000          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
Atomic coordinates 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=2S+1=3.

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-2
  9
  1  0  0  8  2
      14782.00000000          0.00053519          0.00000000
       2217.30000000          0.00413750         -0.00000193
        504.74000000          0.02124500         -0.00005796
        142.87000000          0.08245300         -0.00079494
         46.30000000          0.23671000         -0.00731250
         16.33700000          0.44039000         -0.04057400
          5.98280000          0.36465000         -0.09159400
          1.67180000          0.00000000          0.20940000
  1  0  0  1  1
          0.64662000          1.00000000
  1  0  0  1  1
          0.21669000          1.00000000
  1  1  1  4  1
         60.42400000          0.00689490
         13.93500000          0.04900500
          4.15310000          0.18255000
          1.41580000          0.37633000
  1  1  1  1  1
          0.47549000          1.00000000
  1  1  1  1  1
          0.14529000          1.00000000
  1  2  2  1  1
          2.20000000          1.00000000
  1  2  2  1  1
          0.65000000          1.00000000
  1  3  3  1  1
          1.10000000          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
exercises/2014_ethz_mmm/reaction_energy.1395847748.txt.gz · Last modified: 2020/08/21 10:14 (external edit)