HW_8_Ken

ChatGPT

•Calculate the structure and frequencies of XHn (X = H~Ne) by using B3LYP theoretical method with 6-31+G(d,p) then compare with the experimental values.

few

Reference: National Institute of Standards and Technology 

 -->Both methods use aug-cc-pVTZ with relatively small errors.

 

frequency Unit: cm-1 　 　 　 　 　 　 　 　
H2 4465.7 　 　 　 　 　 　 　 　
exp 4161.2 　 　 　 　 　 　 　 　
Absolute error 304.48 　 　 　 　 　 　 　 　
LiH 1402 　 　 　 　 　 　 　 　
exp 1359.7 　 　 　 　 　 　 　 　
Absolute error 42.3 　 　 　 　 　 　 　 　
BeH2 735.9 735.9 2038.4 2260.6 　 　 　 　 　
exp 697.9 　 　 2159.1 　 　 　 　 　
Absolute error 38 　 　 101.5 　 　 　 　 　
BH3 1157.6 1205.2 1205.2 2576.8 2704.4 2704.4 　 　 　
exp 1147.5 1196.7 　 2601.6 　 　 　 　 　
Absolute error 10.1 8.5 　 -24.8 　 　 　 　 　
CH4 1347.3 1347.3 1347.3 1563.8 1563.8 3037.1 3150.1 3150.1 3150.1
exp 1306 　 　 1534 　 2917 3019 　 　
Absolute error 41.3 　 　 29.8 　 120.1 131.1 　 　
NH3 1000.3 1673.6 1673.6 3484.7 3627.6 3627.6 　 　 　
exp 950 1627 　 3337 3444 　 　 　 　
Absolute error 50.3 46.6 　 147.7 183.6 　 　 　 　
H2O 1603.4 3809.6 3931.5 　 　 　 　 　 　
exp 1595 3657 3756 　 　 　 　 　 　
Absolute error 8.4 152.6 175.5 　 　 　 　 　 　
HF 4069.8 　 　 　 　 　 　 　 　
exp 3961.4 　 　 　 　 　 　 　 　
Absolute error 108.37 　 　 　 　 　 　 　 　

Reference: National Institute of Standards and Technology

•Calculate the single point energy of XHn (X = H~Ne) by using CCSD(T) theoretical method with aug-cc-pVTZ ( the structure obtained from the previous homework ), and then use those energy to calculate the standard enthalpy of formation (ΔH°f)  then compare with the experimental values.

Table: Standard enthalpy of formation (kcal/mol)

(unit: kcal/mol)

實驗值

CCSDT/aug-cc-pVTZ
(B3LYP/6-31+G**)

CCSDT/aug-cc-pVTZ
(B3LYP/aug-cc-pVTZ)

CCSDT/aug-cc-pVTZ
(MP2/6-31+G**)

CCSDT/aug-cc-pVTZ
(MP2/aug-cc-pVTZ)

H2

0.0

1.0

1.0

1.2

1.1

LiH

33.6

34.3

34.4

34.3

34.3

BeH2

30.0

42.3

42.4

42.4

42.4

BH3

21.0

27.3

27.3

27.5

27.4

CH4

-17.8

-11.6

-11.3

-11.4

-11.3

NH3

-11.0

-4.2

-4.2

-4.1

-4.1

H2O

-57.8

-53.3

-53.3

-53.3

-53.2

HF

-65.3

-63.3

-63.3

-63.3

-63.2

First use MP2 or B3LYP to calculate the optimization structure, and then use CCSDT to calculate the standard enthalpy of formation heat. 

      

                          B3LYP                                                                   MP2

MAE (unit: kcal/mol) CCSDT/aug-cc-pVTZ
(B3LYP/6-31+G**)		 CCSDT/aug-cc-pVTZ
(B3LYP/aug-cc-pVTZ)		 CCSDT/aug-cc-pVTZ
(MP2/6-31+G**)		 CCSDT/aug-cc-pVTZ
(MP2/aug-cc-pVTZ)
　 4.95 5.04 5.06 5.07

    -->Regardless of the method used to obtain the structure, the error is approximately the same after performing calculations using CCSDT/aug-cc-pVTZ.

 

Reference: National Institute of Standards and Technology (Computational Chemistry Comparison and Benchmark DataBase)