6. Running Typical Calculations

Before entering the detailed documentation of the various features of ORCA it is instructive to provide a chapter that shows how “typical” tasks may be performed. This should make it easier for the user to get started on the program and not get lost in the details of how-to-do-this or how-to-do-that. We hope that the examples are reasonably intuitive.

• 6.1. Single Point Energies and Gradients
  • 6.1.1. Hartree-Fock
    • 6.1.1.1. Standard Single Points
    • 6.1.1.2. Basis Set Options
    • 6.1.1.3. SCF and Symmetry
    • 6.1.1.4. SCF and Memory
  • 6.1.2. MP2
    • 6.1.2.1. MP2 and RI-MP2 Energies
    • 6.1.2.2. Frozen Core Options
    • 6.1.2.3. Orbital Optimized MP2 Methods
    • 6.1.2.4. MP2 and RI-MP2 Gradients
    • 6.1.2.5. MP2 Properties, Densities and Natural Orbitals
    • 6.1.2.6. Explicitly correlated MP2 calculations
    • 6.1.2.7. Local MP2 calculations
    • 6.1.2.8. Local MP2 derivatives
  • 6.1.3. Coupled-Cluster and Coupled-Pair Methods
    • 6.1.3.1. Basics
    • 6.1.3.2. Coupled-Cluster Densities
    • 6.1.3.3. Static versus Dynamic Correlation
    • 6.1.3.4. Basis Sets for Correlated Calculations. The case of ANOs.
    • 6.1.3.5. Automatic extrapolation to the basis set limit
    • 6.1.3.6. Explicitly Correlated MP2 and CCSD(T) Calculations
    • 6.1.3.7. Frozen Core Options
    • 6.1.3.8. Local Coupled Pair and Coupled-Cluster Calculations
    • 6.1.3.9. Cluster in molecules (CIM)
    • 6.1.3.10. Arbitrary Order Coupled-Cluster Calculations
  • 6.1.4. Density Functional Theory
    • 6.1.4.1. Standard Density Functional Calculations
    • 6.1.4.2. DFT Calculations with RI
    • 6.1.4.3. Hartree–Fock and Hybrid DFT Calculations with RIJCOSX
    • 6.1.4.4. Hartree–Fock and Hybrid DFT Calculations with RI-JK
    • 6.1.4.5. DFT Calculations with Second Order Perturbative Correction (Double-Hybrid Functionals)
    • 6.1.4.6. DFT Calculations with Atom-pairwise Dispersion Correction
    • 6.1.4.7. DFT Calculations with Range-Separated Hybrid Functionals
    • 6.1.4.8. DFT Calculations with Range-Separated Double Hybrid Functionals
  • 6.1.5. Quadratic Convergence
  • 6.1.6. Counterpoise Correction
  • 6.1.7. Complete Active Space Self-Consistent Field Method
    • 6.1.7.1. Introduction
    • 6.1.7.2. A simple Example
    • 6.1.7.3. Starting Orbitals
      • 6.1.7.3.1. Atomic Valence Active Space
    • 6.1.7.4. CASSCF and Symmetry
    • 6.1.7.5. RI, RIJCOSX and RIJK approximations for CASSCF
    • 6.1.7.6. Robust Convergence with TRAH-CASSCF
    • 6.1.7.7. Breaking Chemical Bonds
    • 6.1.7.8. Excited States
    • 6.1.7.9. CASSCF Natural Orbitals as Input for Coupled-Cluster Calculations
    • 6.1.7.10. Large Scale CAS-SCF calculations using ICE-CI
  • 6.1.8. N-Electron Valence State Perturbation Theory (NEVPT2)
  • 6.1.9. Complete Active Space Perturbation Theory: CASPT2 and CASPT2-K
  • 6.1.10. 2nd order Dynamic Correlation Dressed Complete Active Space method (DCD-CAS(2))
  • 6.1.11. Full Configuration Interaction Energies
  • 6.1.12. Efficient Calculations with Atomic Natural Orbitals
  • 6.1.13. Local-SCF Method
  • 6.1.14. Adding finite electric field
• 6.2. SCF Stability Analysis
• 6.3. Geometry Optimizations, Surface Scans, Transition States, MECPs, Conical Intersections, IRC, NEB
  • 6.3.1. Geometry Optimizations
  • 6.3.2. Numerical Gradients
  • 6.3.3. Some Notes and Tricks
  • 6.3.4. Initial Hessian for Minimization
  • 6.3.5. Coordinate Systems for Optimizations
  • 6.3.6. Constrained Optimizations
  • 6.3.7. Constrained Optimizations for Molecular Clusters (Fragment Optimization)
  • 6.3.8. Adding Arbitrary Wall Potentials
  • 6.3.9. Relaxed Surface Scans
    • 6.3.9.1. Multidimensional Scans
  • 6.3.10. Multiple XYZ File Scans
  • 6.3.11. Transition States
    • 6.3.11.1. Introduction to Transition State Searches
    • 6.3.11.2. Hessians for Transition State Calculations
    • 6.3.11.3. Special Coordinates for Transition State Optimizations
  • 6.3.12. MECP Optimization
  • 6.3.13. Conical Intersection Optimization
  • 6.3.14. Constant External Force - Mechanochemistry
  • 6.3.15. Intrinsic Reaction Coordinate
  • 6.3.16. Printing Hessian in Internal Coordinates
  • 6.3.17. Using model Hessian from previous calculations
  • 6.3.18. Geometry Optimizations using the L-BFGS optimizer
  • 6.3.19. Nudged Elastic Band Method
• 6.4. GOAT: global geometry optimization and ensemble generator
  • 6.4.1. GOAT simple usage example - Histidine
  • 6.4.2. Understanding the output
  • 6.4.3. The final ensemble
  • 6.4.4. GOAT-ENTROPY: expanding ensemble completeness by maximizing entropy
  • 6.4.5. More on the \(\Delta S_{\rm conf}\)
    • 6.4.5.1. Finding rotamers automatically
  • 6.4.6. GOAT-EXPLORE: global minima of atomic clusters or topology-free free PES searches
  • 6.4.7. GOAT-REACT: an algorithm for automatic reaction pathway exploration
  • 6.4.8. Some general observations
    • 6.4.8.1. Default frozen coordinates during uphill step
    • 6.4.8.2. Parallelization of GOAT
    • 6.4.8.3. Tips and extra details
  • 6.4.9. Basic keyword list
• 6.5. Vibrational Frequencies
  • 6.5.1. Mass dependencies
• 6.6. Excited States Calculations
  • 6.6.1. Excited States with RPA, CIS, CIS(D), ROCIS and TD-DFT
    • 6.6.1.1. General Use
    • 6.6.1.2. Spin-Flip
    • 6.6.1.3. Population analysis
    • 6.6.1.4. Use of TD-DFT for the Calculation of X-ray Absorption Spectra
    • 6.6.1.5. Excited State Geometry Optimization
      • 6.6.1.5.1. Root Following Scheme for Difficult Cases
      • 6.6.1.5.2. Criteria to Follow IROOTs - starting from ORCA6
    • 6.6.1.6. Doubles Correction
    • 6.6.1.7. Spin-orbit coupling
      • 6.6.1.7.1. SOC and ECPs
      • 6.6.1.7.2. Geometry Optimization of SOC States
    • 6.6.1.8. Transient spectra
    • 6.6.1.9. Non-adiabatic coupling matrix elements
      • 6.6.1.9.1. NACMEs with built-in electron-translation factor
    • 6.6.1.10. Numerical non-adiabatic coupling matrix elements
    • 6.6.1.11. Restricted Open-shell CIS
  • 6.6.2. Excited States for Open-Shell Molecules with CASSCF Linear Response (MC-RPA)
    • 6.6.2.1. General Use
    • 6.6.2.2. Capabilities
  • 6.6.3. Excited States with EOM-CCSD
    • 6.6.3.1. General Use
    • 6.6.3.2. Capabilities
  • 6.6.4. Excited States with ADC2
    • 6.6.4.1. General Use
    • 6.6.4.2. Capabilities
  • 6.6.5. Excited States with STEOM-CCSD
    • 6.6.5.1. General Use
    • 6.6.5.2. Capabilities
  • 6.6.6. Excited States with IH-FSMR-CCSD
    • 6.6.6.1. General Use
    • 6.6.6.2. Capabilities
  • 6.6.7. Excited States with PNO based coupled cluster methods
    • 6.6.7.1. General Use
    • 6.6.7.2. Capabilities
  • 6.6.8. Excited States with DLPNO based coupled cluster methods
    • 6.6.8.1. General Use
  • 6.6.9. Excited States with DeltaSCF
• 6.7. Multireference Configuration Interaction and Pertubation Theory
  • 6.7.1. Introductory Remarks
    • 6.7.1.1. RI-approximation
    • 6.7.1.2. Individual Selection
    • 6.7.1.3. Single excitations
    • 6.7.1.4. Reference Spaces
    • 6.7.1.5. Size Consistency
    • 6.7.1.6. Performance
    • 6.7.1.7. Symmetry
  • 6.7.2. A Tutorial Type Example of a MR Calculation
  • 6.7.3. Excitation Energies between Different Multiplicities
  • 6.7.4. Correlation Energies
  • 6.7.5. Thresholds
    • 6.7.5.1. Reference Values for Total Energies
    • 6.7.5.2. Convergence of Single Reference Approaches with Respect to T\(_{\text{sel} }\)
    • 6.7.5.3. Convergence of Multireference Approaches with Respect to T\(_{\text{pre} }\)
  • 6.7.6. Energy Differences - Bond Breaking
  • 6.7.7. Energy Differences - Spin Flipping
  • 6.7.8. Potential Energy Surfaces
  • 6.7.9. Multireference Systems - Ozone
  • 6.7.10. Size Consistency
  • 6.7.11. Efficient MR-MP2 Calculations for Larger Molecules
  • 6.7.12. Keywords
• 6.8. MR-EOM-CC: Multireference Equation of Motion Coupled-Cluster
  • 6.8.1. A Simple MR-EOM Calculation
  • 6.8.2. Capabilities
  • 6.8.3. Perturbative MR-EOM-PT
• 6.9. Solvation
• 6.10. ORCA SOLVATOR: Automatic Placement of Explicit Solvent Molecules
  • 6.10.1. First Example: Adding Water to a Histidine
  • 6.10.2. Other Solvents
  • 6.10.3. The Stochastic Method for Multiple Solvents
  • 6.10.4. Creating a Droplet
  • 6.10.5. Creating a Droplet with a Defined Radius
• 6.11. Relativistic Calculations
  • 6.11.1. Basis sets for relativistic calculations
  • 6.11.2. Scalar-relativistic gradients and properties
  • 6.11.3. Exact two-component method (X2C)
  • 6.11.4. Douglas-Kroll-Hess (DKH)
  • 6.11.5. ZORA and IORA
• 6.12. Calculation of Properties
  • 6.12.1. Population Analysis and Related Things
  • 6.12.2. Absorption and Fluorescence Bandshapes using ORCA_ASA
  • 6.12.3. IR/Raman Spectra, Vibrational Modes and Isotope Shifts
    • 6.12.3.1. IR Spectra
    • 6.12.3.2. Overtones, Combination bands and Near IR spectra via NEARIR
      • 6.12.3.2.1. Overtones and Combination bands
      • 6.12.3.2.2. Near IR spectra
      • 6.12.3.2.3. Using other methods for the VPT2 correction
    • 6.12.3.3. Vibrational Circular Dichroism (VCD) Spectra
    • 6.12.3.4. Raman Spectra
    • 6.12.3.5. Resonance Raman Spectra
    • 6.12.3.6. NRVS Spectra
    • 6.12.3.7. Animation of Vibrational Modes
    • 6.12.3.8. Isotope Shifts
  • 6.12.4. Thermochemistry
  • 6.12.5. Anharmonic Analysis and Vibrational Corrections using VPT2/GVPT2 and orca_vpt2
    • 6.12.5.1. Vibrational corrections of molecular properties using VPT2
  • 6.12.6. Electrical Properties
  • 6.12.7. NMR Chemical Shifts
  • 6.12.8. NMR Spin-Spin Coupling Constants
    • 6.12.8.1. NMR Spectra
    • 6.12.8.2. Visualizing shielding tensors using orca_plot
  • 6.12.9. Hyperfine and Quadrupole Couplings
  • 6.12.10. The EPR g-Tensor and the Zero-Field Splitting Tensor
  • 6.12.11. Mössbauer Parameters
  • 6.12.12. Broken-Symmetry Wavefunctions and Exchange Couplings
    • 6.12.12.1. Approximate Spin Projection Method
• 6.13. Local Energy Decomposition
  • 6.13.1. Closed shell LED
  • 6.13.2. Example: LED analysis of intermolecular interactions
  • 6.13.3. Open shell LED
  • 6.13.4. Dispersion Interaction Density plot
  • 6.13.5. Automatic Fragmentation
  • 6.13.6. Additional Features, Defaults and List of Keywords
• 6.14. The Hartree-Fock plus London Dispersion (HFLD) method for the study of Noncovalent Interactions
• 6.15. ORCA MM Module
  • 6.15.1. ORCA Forcefield File
    • 6.15.1.1. How to generate the ORCA Forcefield File
      • 6.15.1.1.1. Conversion from psf or prmtop files to ORCAFF.prms: convff
      • 6.15.1.1.2. Divide a forcefield file: splitff
      • 6.15.1.1.3. Merge forcefield files: mergeff
      • 6.15.1.1.4. Repeat forcefield files: repeatff
      • 6.15.1.1.5. Divide a forcefield file: splitpdb
      • 6.15.1.1.6. Merge PDB files: mergepdb
      • 6.15.1.1.7. Create simple force field: makeff
      • 6.15.1.1.8. Get standard hydrogen bond lengths: getHDist
      • 6.15.1.1.9. Create ORCAFF.prms file for IONIC-CRYSTAL-QMMM
  • 6.15.2. Speeding Up Nonbonded Interaction Calculation
    • 6.15.2.1. Force Switching for LJ Interaction
    • 6.15.2.2. Force Shifting for Electrostatic Interaction
    • 6.15.2.3. Neglecting Nonbonded Interactions Within Non-Active Region
  • 6.15.3. Rigid Water
  • 6.15.4. Available Keywords for the MM module
• 6.16. ORCA Multiscale Implementation
  • 6.16.1. General Settings and Input Structure
    • 6.16.1.1. Overview on Combining Multiscale Features with other ORCA Features
    • 6.16.1.2. Overview on Basic Aspects of the Multiscale Feature
    • 6.16.1.3. QM Atoms
    • 6.16.1.4. Active and Non-Active Atoms - Optimization, Frequency Calculation, Molecular Dynamics and Rigid MM Water
      • 6.16.1.4.1. Input Format
      • 6.16.1.4.2. Optimization in redundant internal coordinates
      • 6.16.1.4.3. Optimization with the Cartesian L-BFGS Minimizer
      • 6.16.1.4.4. Frequency Calculation
      • 6.16.1.4.5. Nudged Elastic Band Calculations
      • 6.16.1.4.6. Molecular Dynamics
      • 6.16.1.4.7. Rigid MM Water
    • 6.16.1.5. Forcefield Input
    • 6.16.1.6. QM-MM, QM-QM2 and QM2-MM Boundary
      • 6.16.1.6.1. Link Atoms
      • 6.16.1.6.2. Bond Length Scaling factor
      • 6.16.1.6.3. Standard QM-H Bond Length
      • 6.16.1.6.4. Bonded Interactions at the QM-MM Boundary
      • 6.16.1.6.5. Charge Alteration
    • 6.16.1.7. Embedding Types
  • 6.16.2. Additive QMMM
  • 6.16.3. ONIOM Methods
    • 6.16.3.1. Available QM2 Methods
    • 6.16.3.2. Electrostatic Interaction between high and low level
    • 6.16.3.3. Boundary Region
    • 6.16.3.4. Subtractive QM/QM2 Method
      • 6.16.3.4.1. System charges and multiplicities
      • 6.16.3.4.2. Available low level methods
      • 6.16.3.4.3. Solvation
    • 6.16.3.5. QM/QM2/MM Method
      • 6.16.3.5.1. QM2 Atoms
      • 6.16.3.5.2. System charges and multiplicities
      • 6.16.3.5.3. Available low level methods
      • 6.16.3.5.4. Example Input
  • 6.16.4. CRYSTAL-QMMM
    • 6.16.4.1. Charge Convergence between QM and MM region
    • 6.16.4.2. MM-MM Interaction
    • 6.16.4.3. Preparing CRYSTAL-QMMM Calculations
    • 6.16.4.4. MOL-CRYSTAL-QMMM
      • 6.16.4.4.1. Extending the QM Region
      • 6.16.4.4.2. Example Input
    • 6.16.4.5. IONIC-CRYSTAL-QMMM
      • 6.16.4.5.1. Boundary Region
      • 6.16.4.5.2. Extending the QM Region
      • 6.16.4.5.3. Net Charge of the Entire Supercell
      • 6.16.4.5.4. Example Input
      • 6.16.4.5.5. Different QM and MM regions Stored in the PDB file
  • 6.16.5. Additional Keywords
• 6.17. QM/MM via Interfaces to ORCA
  • 6.17.1. ORCA and Gromacs
  • 6.17.2. ORCA and pDynamo
  • 6.17.3. ORCA and NAMD
• 6.18. Excited State Dynamics
  • 6.18.1. Absorption Spectrum
    • 6.18.1.1. The ideal model, Adiabatic Hessian (AH)
    • 6.18.1.2. The simplest model, Vertical Gradient (VG)
    • 6.18.1.3. A better model, Adiabatic Hessian After a Step (AHAS)
    • 6.18.1.4. Other PES options
    • 6.18.1.5. Duschinsky rotations
    • 6.18.1.6. Temperature effects
    • 6.18.1.7. Multistate Spectrum
  • 6.18.2. Fluorescence Rates and Spectrum
    • 6.18.2.1. General Aspects
    • 6.18.2.2. Rates and Examples
  • 6.18.3. Phosphorescence Rates and Spectrum
    • 6.18.3.1. General Aspects
    • 6.18.3.2. Calculation of rates
  • 6.18.4. Intersystem Crossing Rates (unpublished)
    • 6.18.4.1. General Aspects
    • 6.18.4.2. ISC, TD-DFT and the HT effect
  • 6.18.5. Internal Conversion Rates (unpublished)
  • 6.18.6. Resonant Raman Spectrum
    • 6.18.6.1. General Aspects
    • 6.18.6.2. Isotopic Labeling
    • 6.18.6.3. RRaman and Linewidths
  • 6.18.7. ESD and STEOM-CCSD or other higher level methods - the APPROXADEN option
  • 6.18.8. Circularly Polarized Spectroscopies
    • 6.18.8.1. General Aspects
    • 6.18.8.2. Vibration effects on ECD spectra
    • 6.18.8.3. Computation of CP-FLUOR vs CP-PHOS spectra. The case of \(C_{3}H_{6}O\).
    • 6.18.8.4. Use of ABS, ECD PL and CPL as a routine analysis computational tools
  • 6.18.9. Magnetic Circular Dichroism (unpublished)
    • 6.18.9.1. General Aspects
  • 6.18.10. Tips, Tricks and Troubleshooting
• 6.19. The ORCA DOCKER: An Automated Docking Algorithm
  • 6.19.1. Example 1: A Simple Water Dimer
  • 6.19.2. Example 2: A Uracil Dimer
  • 6.19.3. Example 3: Adding Multiple Copies of a Guest
  • 6.19.4. Example 4: Find the Best Guest
  • 6.19.5. Reduced Keyword List
• 6.20. Compound Methods
  • 6.20.1. example
  • 6.20.2. Defining variables
  • 6.20.3. Running calculations
  • 6.20.4. Data manipulation