Molecular Models.

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Presentation transcript:

Molecular Models

Methodology: Modify Wavefunction

Theory: Wavefunction

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

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*

Computation: Electron Correlation

Configuration Interaction (CI) unoccupied occupied

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

Computation: Computation Time

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

Results: Energy

Results: Energy

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).

Problems:Variational Principle