1. Multiply Charged Ions Quantum Chemical Computations Trento, May 2002 Lecture 3

2. Multi-Reference Methods

3. Unrestricted Hartree-Fock

4. Multi-Configuration Self- Consistent Field (MCSCF) Bond Dissociation Multi-configuration nature E.g. O 3 TiF 3+ ( 1  + )

5. MR-CI(SD) Only MR-CISD practical Size inconsistent (“Davidson correction”) MR-ACPF, MR-AQCC CASPT2, MR-MBPT, CASMP2

6. Excited States CIS, TD-DFT, CCSD-EOM MC-SCF (Spin, symmetry)

7. He 2 2+ – avoided crossing

8. Density Functional Theory Hohenberg & Kohm: E = E(  ) E = V NN + T(  ) + V Ne (  ) + V ee (  ) Kohn-Sham:  =  i 2

9. DFT – 2 E(  ) = V NN + T S (  ) + V Ne (  ) + J(  )+E XC (  ) E XC (  ) not known LDA, BP86, BLYP, GGA (PW91), B3LYP

10. Relativity Scalar Effects Spin-orbit Coupling

11. Accuracy HF: good geometries MP2: good geometry, energy when appropriate DFT: good geom + energy CCSD(T) / MR-CISD: excellent energetics where applicable

12. Expense HF: N 4 MP2: N 5 DFT: N 3 CCSD(T): N 7 MCSCF, MR-CISD: e N Efficient codes for HF, MP2, DFT, CCSD(T)

13. Programs Gaussian (98) - John Pople ACES II (R. J. Bartlett, Floride - CC methods) ADF (Amsterdam, DFT) CADPAC (Cambridge, U.K.) Columbus (I. Shavitt, Columbus, Ohio) Dalton (Norway) Gamess-USA (M. Gordon, M. Schmidt, Iowa) Gamess-UK (Daresbury, UK) Jaguar (Schrödinger, inc - R. Friesner, Portland, Oregon) MOLCAS (Lund, Suède, B. Roos) MOLPRO (P. Knowles / H.-J. Werner, UK/Allemagne) NWChem (PNL, USA) Q-Chem (Gill, Head-Gordon, Schaeffer, …) Spartan (W. Hehre, Wavefunction inc.) Turbomole (R. Ahlrichs)