1. Molecular Models

2. Methodology: Modify Wavefunction

3. Theory: Wavefunction

4. Computation: Basis Set
AO Type
Functional Forms s
e-ar2 Px
x e-ar2 Py
y e-ar2 Pz
z e-ar2
dx2
x2 e-ar2
dy2
y2 e-ar2
dz2
z2 e-ar2
dxy
xy e-ar2
dxz
xz e-ar2
dyz
yz e-ar2

5. Computation: Basis Set
# functions
STO-3G 5
6-31G 9
6-311G 13
3-21G
6-31G* 15
6-311G*
18*
4-31G
6-31+G* 19
6-311+G*
22*

6. Computation: Electron Correlation

7. Configuration Interaction (CI)
unoccupied
occupied

8. Moller Plesset (MP) Hartree-Fock close to Full Hamiltonian
Perturbation

9. Computation: Computation Time

10. Results: Geometry Molecule Coordinate HF MP2 CCSD MP4 CCSD(T)
Error in Bond Length (Å)
H2O
O-H
-0.006
0.005
0.004
NH3
N-H
-0.011
0.002
0.003
CH4
C-H
-0.001
0.006
C2H2
C-C
-0.002
-0.012
0.024
0.007
0.016
0.008
0.025
0.023
CH2O
C=O
-0.005
-0.015
0.022
0.015
0.021
HCN
C-N
-0.003
-0.017
0.032
0.019
0.030
-0.008
-0.010
0.017
0.031
CO2
C-O
0.012
0.028
0.018
Average Abs. Error ()
-0.009
0.013
0.009
Error in Bond Angle (deg.)
H-O-H
2.1
-0.1
0.1
0.0
H-N-H
1.5
-0.2
-0.3
-0.4
CH20
H-C-O
-0.6
Average Error (deg.)
1.3

11. Results: Energy

12. Results: Energy

13. Results: Charge
Example: Chlorine atomic charge in CH3Cl, HF Mulliken and NPA charges ;
calculated with many basis sets (at the HF/6-31G* optimized geometry).

14. Problems:Variational Principle