Comparing enthalpy, entropy, heat of formation, and ground state energy of HCN between Spartan, Gaussian and Cerius:
|
Program |
Calculation Method |
Delta H |
Delta S |
Delta G |
Keq |
Ea |
A |
|
Spartan |
Density Functional |
16.794 kcal/mol |
.148 cal/mol K |
16.794 kcal/mol |
6.288 E -13 |
46.782 kcal/mol |
5.386 E 13 |
|
Gaussian |
Hartree Fock |
12.052 kcal/mol |
.043 cal/mol K |
11.810 kcal/mol |
2.198 E -9 |
48.461 kcal/mol |
5.248 E 13 |
|
Cerius 2 |
PM3 |
23.650 kcal/mol |
.491 cal/mol K |
23.503 kcal/mol |
7.528 E -18 |
75.135 kcal/mol |
6.026 E 13 |
What are some of the differences between the three programs? Where do these differences come from?Concept tests: Think or write out an answer, then check your answer.
1. What is the most fundamental postulate of quantum mechanics?
2. What is Schrödinger's equation and its constituent parts?
3. What is an operator?
4. What is an eigenfunction and eigenvalue?
5. What is the physical significance of the solution to the Schrödinger equation?
6. What can molecular modeling do for a chemical engineer?
7. How does the computational method effect the computation time?
8. What are the two most common references for zero energy used when calculating heats of formation and ground state energies?
9. What is activation energy?
10. What thermodynamic quantity is used to calculate the equilibrium constant?
11. What thermodynamic quantity is used to calculate the preexponential factor?
12. What areas of chemical engineering can these computational chemistry programs be applied to?
13. What reasons would a large industrial company have for not building a large reactor solely on data from a computational chemistry software package?
