HW_8_Ken
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•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.
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 |
CCSDT/aug-cc-pVTZ |
CCSDT/aug-cc-pVTZ |
CCSDT/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)
