3. Model Chemistries¶
Model Chemistries
- 3.1. Wavefunction Types: RHF/RKS, UHF/UKS, ROKS and more
- 3.2. Hartree Fock Theory
- 3.3. Density Functional Theory (DFT)
- 3.4. Dispersion Corrections
- 3.5. Semiempirical Methods
- 3.6. Composite Methods (3c methods)
- 3.7. Analytic Density Functional Theory (ADFT)
- 3.8. Random Phase Approximation (RPA)
- 3.9. Perturbation Theory - MP2
- 3.9.1. Standard (non-RI) MP2
- 3.9.2. RI-MP2
- 3.9.3. Calculating MP2 and RI-MP2 Energies
- 3.9.4. Frozen Core Options
- 3.9.5. MP2 and RI-MP2 Gradients
- 3.9.6. RIJCOSX-RI-MP2 Gradients
- 3.9.7. MP2 and RI-MP2 Second Derivatives
- 3.9.8. MP2 Properties, Densities and Natural Orbitals
- 3.9.9. RI-MP2 and Double-Hybrid DFT Response Properties
- 3.9.10. Local MP2 calculations
- 3.9.11. Local MP2 gradients
- 3.9.12. Explicitly correlated MP2 calculations
- 3.9.13. MP2 in “Double-Hybrid” Density Functional Theory
- 3.9.14. Orbital Optimized MP2 Methods
- 3.9.15. Regularized MP2 and RI-MP2
- 3.9.16. Keywords
- 3.10. Coupled Cluster and CI Theories (MDCI)
- 3.10.1. Theory
- 3.10.2. Basic Usage
- 3.10.3. Coupled-Cluster Densities
- 3.10.4. Static versus Dynamic Correlation
- 3.10.5. Basis Sets for Correlated Calculations. The case of ANOs.
- 3.10.6. The Coupled Cluster S-Diagnostic
- 3.10.7. Explicitly Correlated Methods: F12-MP2 and F12-CCSD(T)
- 3.10.8. Automatic extrapolation to the basis set limit
- 3.10.9. Cluster in molecules (CIM)
- 3.10.10. Local correlation (DLPNO)
- 3.10.11. Multi-Level Calculations
- 3.10.12. Multi-Level Calculations for IP and EA-EOM-DLPNO-CCSD
- 3.10.13. Excited States (EOM/STEOM/ADC)
- 3.10.14. Keywords
- 3.11. Correlated Methods using Automatic Code Generation (AUTOCI)
- 3.11.1. Introduction
- 3.11.2. Basis Usage / List of Features
- 3.11.3. Analytic Nuclear Gradients with AUTOCI
- 3.11.4. AUTOCI Response Properties via Analytic Derivatives
- 3.11.5. Fully Internally Contracted MRCI (FIC-MRCI)
- 3.11.6. Fully Internally Contracted MRCC (FIC-MRCC)
- 3.11.7. Fully Internally Contracted NEVPT (FIC-NEVPT4(SD)/FIC-NEVPT3/FIC-NEVPT2)
- 3.11.8. FIC Ansatz: Unrelaxed Densities and Natural Orbitals
- 3.11.9. Keywords
- 3.12. Arbitrary Order Coupled-Cluster (MRCC interface)
- 3.13. Complete and Incomplete Active Space Self-Consistent Field (CASSCF and RAS/ORMAS)
- 3.13.1. Introduction
- 3.13.2. Theory
- 3.13.3. Basic Usage
- 3.13.3.1. Orbital Optimization (2-step approach)
- 3.13.3.2. Orbital Optimization (1-step approach): Robust Convergence with TRAH-CASSCF
- 3.13.3.3. Using the RI Approximation
- 3.13.3.4. Final Orbitals: Canonicalization Choices
- 3.13.3.5. CI Solvers (CSFCI, ACCCI, …, ICE)
- 3.13.3.6. Model Spaces: CAS, RAS and ORMAS
- 3.13.3.7. Restricted Active Space (RAS)
- 3.13.3.8. Occupation Restricted Multiple Active Spaces (ORMAS)
- 3.13.3.9. The RASCI and ORMAS Module
- 3.13.4. Keywords
- 3.13.5. A simple Example: Be Ground State
- 3.13.6. Guess: Natural Orbitals Example
- 3.13.7. Guess: Atomic Valence Active Space (AVAS)
- 3.13.8. Example: Symmetry
- 3.13.9. Example: Breaking Chemical Bonds
- 3.13.10. Example: Excited States
- 3.13.11. Example: Large Active Spaces using ICE-CI
- 3.13.12. Example: Geometry Optimization
- 3.13.13. Example: Natural Orbitals as Input for Coupled-Cluster Calculations
- 3.13.14. CASSCF Densities
- 3.13.15. CASSCF Properties
- 3.13.16. 1- and 2-shell Abinitio Ligand Field Theory (AILFT)
- 3.13.17. Extended Space Ab initio Ligand Field Theory (ESAILFT)
- 3.13.18. Core Excited Spectra: CAS-CI/RAS-CI XAS/RIXS
- 3.13.19. Core Excited Spectra: CAS-CI/RAS-CI XES
- 3.14. Approximate Full CI Calculations in Subspace: ICE-CI
- 3.14.1. Introduction
- 3.14.2. The ICE-CI and CIPSI Algorithms
- 3.14.3. A Simple Example Calculation
- 3.14.4. Accuracy
- 3.14.5. Scaling behavior
- 3.14.6. Accuracy of the Wavefunction
- 3.14.7. Potential Energy Surfaces
- 3.14.8. Excited States
- 3.14.9. Tips and Tricks
- 3.14.10. Large-scale approximate CASSCF: ICE-SCF
- 3.14.11. Keywords
- 3.14.12. A Technical Note:
orcacclib
- 3.15. Density Matrix Renormalization Group (DMRG)
- 3.16. N-Electron Valence State Perturbation Theory (NEVPT2)
- 3.16.1. A simple Example:
Ground State - 3.16.2. RI, RIJK and RIJCOSX Approximation
- 3.16.3. Beyond the RI approximation: DLPNO-NEVPT2
- 3.16.4. Explicit Correlation: NEVPT2-F12 and DLPNO-NEVPT2-F12
- 3.16.5. Handling of Reduced Density Matrices
- 3.16.6. False Intruder States and Imaginary Shift
- 3.16.7. Large Active Spaces: ICE-NEVPT2
- 3.16.8. Large Active Spaces: DMRG-NEVPT2
- 3.16.9. Selecting or Specific States for NEVPT2
- 3.16.10. Unrelaxed Densities and Natural Orbitals
- 3.16.11. State-averaged SC-NEVPT2
- 3.16.12. Quasi-Degenerate SC-NEVPT2
- 3.16.13. Keywords
- 3.16.1. A simple Example:
- 3.17. Complete Active Space Peturbation Theory (CASPT2 and CASPT2-K)
- 3.18. CASSCF and DFT
- 3.19. Multireference Configuration Interaction and Pertubation Theory (uncontracted)
- 3.19.1. Introductory Remarks
- 3.19.2. RI-approximation
- 3.19.3. Individual Selection
- 3.19.4. A Tutorial Type Example of a MR Calculation
- 3.19.5. Excitation Energies between Different Multiplicities
- 3.19.6. Correlation Energies
- 3.19.7. Thresholds
- 3.19.8. Energy Differences - Bond Breaking
- 3.19.9. Energy Differences - Spin Flipping
- 3.19.10. Potential Energy Surfaces
- 3.19.11. Multireference Systems - Ozone
- 3.19.12. Size Consistency
- 3.19.13. Efficient MR-MP2 Calculations for Larger Molecules
- 3.19.14. Properties Calculation Using the SOC Submodule
- 3.19.14.1. Zero-Field Splitting
- 3.19.14.2. Local Zero-Field Splitting
- 3.19.14.3. Zero-Field Splitting from an excited Multiplet
- 3.19.14.4. g-Tensor
- 3.19.14.5. Magnetization and Magnetic Susceptibility
- 3.19.14.6. MCD and Absorption Spectra
- 3.19.14.7. Addition of Magnetic Fields
- 3.19.14.8. Relativistic Picture Change in Douglas-Kroll-Hess SOC and Zeeman Operators
- 3.19.14.9. X-ray Spectroscopy
- 3.19.15. Keywords
- 3.20. Multireference Equation of Motion Coupled-Cluster (MR-EOM-CC)
- 3.20.1. A Simple MR-EOM-CC Calculation
- 3.20.2. Capabilities
- 3.20.3. Perturbative MR-EOM-CCPT
- 3.20.4. Details on the Multireference Equation of Motion Coupled-Cluster (MR-EOM-CC ) Theory
- 3.20.5. An Orbital Selection Scheme for More Efficient Calculations of Excitation Spectra with MR-EOM
- 3.20.6. Nearly Size Consistent Results with MR-EOM-CC by Employing an MR-CEPA(0) Shift in the Final Diagonalization Procedure
- 3.20.7. Perturbative MR-EOM-CCPT
- 3.21. Dynamic Correlation Dressed CAS
- 3.22. Full Configuration Interaction
- 3.23. Molecular Mechanics
- 3.23.1. Combining the MM module with other ORCA Features
- 3.23.2. Molecular Mechanics Force Field in ORCA
- 3.23.2.1. Supported Force Field Types
- 3.23.2.2. How to generate and manipulate the ORCA Force Field File
- 3.23.2.2.1. Conversion from other formats to ORCAFF.prms: convff
- 3.23.2.2.2. Divide a force field file: splitff
- 3.23.2.2.3. Merge force field files: mergeff
- 3.23.2.2.4. Repeat force field files: repeatff
- 3.23.2.2.5. Divide a PDB file: splitpdb
- 3.23.2.2.6. Merge PDB files: mergepdb
- 3.23.2.2.7. Create simple force field: makeff
- 3.23.2.2.8. Get standard hydrogen bond lengths: getHDist
- 3.23.2.2.9. Create ORCAFF.prms file for IONIC-CRYSTAL-QMMM
- 3.23.3. Speeding Up Nonbonded Interaction Calculation
- 3.23.4. Rigid Waters
- 3.23.5. Available Keywords for the MM module