Topic: DFT, scripting in Python

Download these files. Be prepared: Gaussian is needed

Lecture slides (slides-2020)

Practice (selectively)

• Estimate the dipole moment of CO molecule using different approaches [diatomic]
  • Investigate basis set convergence
  • Investigate MP convergence
  • Investigate CI and CC convergence
  • Investigate density functional dependence. Can we say that LDA "over-delocalizes" electron density and HF "over-localizes" it?
  • Compare with experimental data and other calculations (see CCCBDB)
  • The same for equilibrium bond length, force constant, and dipole moment derivative
  • Analyze methods in terms of computing time
• Dynamic correlations in CO molecule [diatomic]
  • Compare MO and NO of CO molecule
  • Analyze NO occupations
  • Explain absence of basis set convergence for small virtual space CI
• What is the difference between bonding in CO and H2CO molecules? Compare charge distribution. Draw orbital interaction diagram
• Investigate density functional dependence of the ionization potential of ethylene molecule [ethylene_IPEA]
• Observe Koopmans' theorem violation in approximate DFT [benzene_IP.txt]
• SCF convergence problems related to wrong initial guess [NDI]
  • Calculate adiabatic IP for thiophene by CAM-B3LYP/6-31G*
  • Calculate cation NO for NDI molecule with CAM-B3LYP and compare it with HOMO
  • Analyze initial guess for MOs and correct it
  • Why there is no such artefact for another conformer of NDI molecule (molec-a)
  • Check if no-symmetry keyword will help
  • Why there is no such artefact for B3LYP
  • Solvate both ground and excited cation states in water
• Computational artifacts:
  • Often we have to apply methods beyond their validity (because usually we solve mathematically ill-defined problems) ⇒ use multiple methods
  • Madelung constant
  • Nonplanarity of benzene (Moran2006, Lawler2008, Walewski2014 vs Shishkin2011)
  • see CCCBDB for other examples

Reading

• Cramer chapter 8
• Jensen chapter 6
• Burke: The ABC of DFT, Tutorial slides, Review 2012
• K Lejaeghere etal, Reproducibility in density functional theory calculations of solids, Sci 351, 1415 (2016)
• J Witte, J B Neaton, M Head-Gordon, Push it to the limit: Characterizing the convergence of common sequences of basis sets for intermolecular interactions as described by density functional theory, JCP 144, 194306 (2016) – copy