Chapter 4 Methods in Molecular Modelling

1
Chapter 4Methods in Molecular Modelling

• 01403345
• Piti Treesukol

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Optimization Procedure
Specify Initial Structure (R)
Guess Wave Function
Adjust ?(R,r)
Determine E(R,r)
SCF
Specify New Structure
Calculate ?E/??
Minimum E(R,r)?
Calculate ?E/?R
Minimum E(R)?
3
??????????????? HF

• ??????????????????????????????????????????????
  (electron correlation) ???????????????
  Self-consistent Field
• ?????? Single Slater-determinant
  ????????????????????????? ????????????????????
  electronic configuration ????????
• ?????????????????????????????????????????
• ????????????????????????? HF ???????????? 90
  ?????????????? (exact energy) ???????
  ????????????????? 10 ????????????????????????????
  ????

4
Correlation Methods

• ??????????????????????????????????????????????????
  Hartree-Fock ????????????????????????????????????
  ?? ? ??????????????????????????????? ?
  ??????????????????????????????????????????? ?
  ??????????????????????????????????????????????????
  ??????
• Perturbation Method (MP2, MP3 etc.)
• Configuration Interaction (CI)
• Multi-reference CI (MRCI)
• Couple Cluster (CC)

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Methods

• Quantum Chemistry
• Ab-initio Calculations
• Semi-empirical Calculations
• Density Functional Thoery
• Plane wave calculations
• Classical Chemistry
• Molecular Dynamics
• Molecular Mechanics
• Other Approaches

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Ab-initio Calculations

• Hartree-Fock methods
• Hartree-Fock (HF/ROHF/UHF)
• ?Post-Hartree-Fock methods
• Møller-Plesset perturbation theory (MPn)
• Configuration interaction (CI)
• Coupled cluster (CC)
• Quadratic configuration interaction (QCI)
• Quantum chemistry composite methods (G1, G2, CBS)
• Multi-reference methods
• Multi-configurational self-consistent field
  (MCSCF)
• Multi-reference configuration interaction (MRCI)
• Complete Active Space Perturbation Theory (CASPTn)

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Density Functional Theory (DFT)

• ???????????????????????????????????????????????
  ??????????????????????????????????????????????????
  ?????????????????? ??(x1,y1,z1,x2,y2, z2,,
  xn,yn,zn) ????????????????????????????????????????
  ??????
• Hohenberg-Kohn ???????????????????????????????????
  ?????? ? ?????????????????????????????????????????
  ?? (?)?????????? ?????????????????????????????????
  ?
• ?????????????????????????????????? ? ?????????
  nucleus-nucleus repulsion

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Density Functionals

• ???? ??? ??????????????????????????
  ?????????? ?
• Local exchange functional (uniform electron gas)
• Beck88 exchange functional
• Gradient-corrected correlation functional
• Hybrid Method
• B3LYP

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Ab Initio and Semi-Empirical Methods

• ????????????????? HF ???????? Correlation method
  ??????????????????????????????????????????????????
  ????????????
• ????????????????????????????????????
  ??????????????????????????????????????????????????
  ??????????????????????????????????????????????????
  ???? ??????????????????????????????
• Ab initio calculation ????????????????????????????
  ???????????? ?????????????????????????????????????
  ?
• Semi-empirical calculation ???????????????????????
  ??????????????????????????????????????????????????
  ????????? ???????????? CNDO MNDO AM1 PM3
• Combinational Methods ????????????????????????????
  ????? ab initio ??????????? ? ????????????????????
  ???????????????????????????????????????????
  ???????????? G2 G3

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Applications of Computational Chemistry
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Computational Chemistry

• ??????????????? Schrödinger ??????????????????????
  ???????????????????? ?????????????????????????????
  ???? ???? ????????????????? ????????????
  ????????????
• ??????????????????????????????????????????????????
  ????????????? ????
• HyperChem ????????? semi-empirical ab initio
• Gaussian03 ????????????????????????????
• VASP
• NWChem