第13周..作業

Calculate the k(rate constant) in different temperature for the following reaction and plot of ln(k) versus 1000/T then compare with the experimental values.

reaction ：

CH4 +OH․→ H2O + CH3․

NH3 +OH․→ H2O + NH2․

method：

MP2/aug-cc-pVTZ

CCSD(T)/aug-cc-pVTZ//MP2/aug-cc-pVTZ

step:

1.Use the temperature command temperature=xxK to add to the input file.

2.Calculate the k( rate constant ) by  

3.compare the differences by using the different Electronic Energies from MP2/aug-cc-pVTZ、CCSDT/aug-cc-pVTZ//MP2/aug-cc-pVTZ

result:

1.CH4 +OH․→ H2O + CH3․

1000/T mp2 ccsd(t)
3.7 -35.7 -32.4
3.36 -34.7 -31.73
2.68 -32.52 -30.12
2.5 -31.9 -29.7
1.67 -29.04 -27.55
1.3 -27.4 -26.3

 

CH4
Exp
T k 1000/T lnk
100 8.20E-20 10 -43.9
150 2.30E-17 6.7 -38.3
200 4.10E-16 5 -35.4
250 2.10E-15 4 -33.8
300 6.70E-15 3.3 -32.6
350 1.60E-14 2.9 -31.7
400 3.40E-14 2.5 -31
450 6.30E-14 2.2 -30.4
500 1.05E-13 2 -29.9
550 1.64E-13 1.8 -29.4
600 2.44E-13 1.7 -29

Unit:kcal/mole

 

10

  • The MP2/aptz has a better description in high temperatures while CCSD(T)/aptz//MP2/aptz with correction has a better description in low temperatures.

2.NH3 +OH․→ H2O + NH2․

1000/T mp2 ccsd(t)
3.7 -38 -31.1
3.36 -37.06 -30.75
2.69 -34.94 -29.9
2.5 -34.4 -28.5
1.67 -31.64 -28.5
1.3 -30.1 -27.8

 

NH3
Exp
T k 1000/T lnk
200 7.90E-15 5 -32.5
300 3.60E-14 3.3 -31
400 9.60E-14 2.5 -30
500 2.00E-13 2 -29.2
600 3.60E-13 1.7 -28.6

Unit:kcal/mole

9

  • The CCSD(T)/aptz//MP2/aptz  has a better description than MP2/aptz.

參考資料

  • https://aip.scitation.org/doi/10.1063/1.4792719
  • https://www.sciencedirect.com/science/article/abs/pii/S0082078485805609?via%3Dihub