林昶廷-第6週作業1024

1.Please use ChatGPT to explore a thematic series of questions within the scope of computational chemistry and follow up with further inquiries about any unfamiliar terms

ChatGPT

2.Use Gaussian or WebMO to calculate the Electron Affinity of Helium、Neon、Argon, by using B3LYP、MP2 and M062X theoretical methods with cc-pVTZ、aug-cc-pVTZ、d-aug-cc-pVTZ basis set, and do some simple statistical analysis.(check your unit、analysis tools)

1.Electron Affinity of Helium、Neon、Argon(Unit:Kcal/mol)

He B3LYP MP2   M062 Expt
cc-pVTZ 376.8 394.5 367.5 11.53
aug-cc-pVTZ 61.9 68.3 62.7
d-aug-cc-pVTZ 10.1 13.2 10.7
NE B3LYP MP2   M062 Expt
cc-pVTZ 629.9 671.9 634.6 27.67
aug-cc-pVTZ 130.2 141.3 131.7
d-aug-cc-pVTZ 28.4 440.4 31.8
Ar B3LYP MP2   M062 Expt
cc-pVTZ 302.7 501.4 301.1 23.06
aug-cc-pVTZ 72.2 77.8 72.8

 

2-1.不同理論下比較基底函數的計算結果

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3.誤差

ABS error(Kcal/mol) He NE Ar MAE
B3LYP/cc-pVTZ 371.78 618.94 294.73 428.48
B3LYP/aug-cc-pVTZ 56.86 119.18 64.20 80.08
B3LYP/d-aug-cc-pVTZ 5.11 17.42 　 11.27
MP2 /cc-pVTZ 389.47 660.87 493.41 514.58
MP2 /aug-cc-pVTZ 63.35 130.30 69.82 87.82
MP2 /d-aug-cc-pVTZ 8.18 24.64 　 16.41
 M062X/cc-pVTZ 362.54 629.62 296.08 429.41
 M062X/aug-cc-pVTZ 57.68 126.68 67.84 84.07
 M062X/d-aug-cc-pVTZ 5.67 26.82 　 16.24

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結論:雖然d-aug-cc-pVTZ算不出來導致數值空缺，但從MAE可以看出基底函數愈複雜則得到的結果愈接近真實值，

 

Try to add an additional set of diffuse functions for the s orbital of He, and the s and p orbitals of Ne and Ar. ( in the 6-31G basis set )

Table.Use B3LYP with 6-31G basis set (Unit:Kcal/mol)

B3lyp He  Ne   Ar
6-31G** 143.2 1009.4 684.1
6-31+G** 71.4 36.9791 464.3
6-31++G** 37.5 29.27 464.5
Exp 11 27.7 23.6

Table.Use MP2 with 6-31G basis set (Unit:Kcal/mol)

 
MP2 He  Ne   Ar
6-31G** 158.6 1237.3 354.7
6-31+G** 46.3 89.3 47.6
6-31++G** 12.2 81.5 45.9
Exp 11 27.7 23.6

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Table.Absolute error(Unit:Kcal/mol)

B3LYP He  Ne   Ar
6-31G** 132.23 998.42 673.05
6-31+G** 60.35 25.98 452.99
6-31++G** 26.52 18.27 453.49
MP2 He  Ne   Ar
6-31G** 147.6 1226.3 343.69
6-31+G** 35.32 78.25 36.64
6-31++G** 1.2 70.54 34.98

結論:增加diffuse functions在趨勢上絕對誤差會愈來愈小

  • Try to use Gaussian or WebMO to optimize the H₃⁺ molecule and calculate the linear dissociation energy according to the formula provided in the PDF lecture.

H2+ H2+àH3++H   

  • Energy of  difference H type 
CISD/aug-cc-pVTZ OPT
H type H3+  H H2 H2+
Hartree -1.27710 -0.49982 -1.16377 -0.53090
Kcal/mol -801.4 -313.6 -730.3 -333.1
  •  linear dissociation energy according to the difference formula 

dissociation energy:(-801.4+-313.6)-(-730.3-333.1)= -51.6