Theoretical Methods: SCF to FCI

Several electronic structure methods are available in the PSI4 package, from Hartree–Fock molecular orbital theory to coupled-cluster theory to full configuration interaction. This section introduces the methods available and some of their most common input parameters. A complete list of standard keywords is provided in Appendix Keywords by Module.

• Notes on Options
• Notes on Psivars
• Alternate Implementations
• HF: Hartree–Fock Theory
  • Introduction
  • Theory
  • Minimal Input
  • Spin/Symmetry Treatment
  • Broken Symmetry
  • Orthogonalization
  • Initial Guess
  • Restarting the SCF
  • Convergence Stabilization
  • ERI Algorithms
  • COSX Exchange
  • LinK Exchange
  • Second-order Convergence
  • Stability Analysis
  • Effective core potentials (ECPs)
  • External potentials and QM/MM
  • Convergence and Algorithm Defaults
  • Recommendations
• DFT: Density Functional Theory
  • Theory
  • Minimal Input
  • Spin/Symmetry Treatment
  • Functional Selection
  • Grid Selection
  • ERI Algorithms
  • IP Fitting
  • Fractional Particle Curves
  • Dispersion Corrections
  • Recommendations
  • Advanced Functional Use and Manipulation
• DFT-NL
  • post-SCF time savings
• DCT: Density Cumulant Theory
  • Theory
  • Methods
  • Iterative Algorithms
  • Analytic Gradients
  • Methods Summary
  • Minimal Input
  • Recommendations
• DF-MP2: Density-Fitted 2nd-Order Møller–Plesset Perturbation Theory
  • Introduction
  • Theory
  • Recommendations
• DLPNO-MP2: Domain-Based Local Pair Natural Orbital MP2
  • Introduction
  • Theory
  • Recommendations
• CC: Coupled Cluster Theory
  • Basic Keywords
  • Larger Calculations
  • Excited State Coupled Cluster Calculations
  • Linear Response (CCLR) Calculations
• FNOCC: Frozen natural orbitals for CCSD(T), QCISD(T), CEPA, and MP4
  • Frozen natural orbitals (FNO)
  • QCISD(T), CCSD(T), MP4, and CEPA
  • Quadratic configuration interaction and coupled cluster
  • Many-body perturbation theory
  • Coupled electron pair approximation
  • Density-fitted coupled cluster
  • Gn theory
  • Supported methods
  • Basic FNOCC Keywords
  • Advanced FNOCC Keywords
• OCC: Orbital-Optimized Coupled-Cluster and Møller–Plesset Perturbation Theories
  • Introduction
  • Theory
  • Convergence Problems
  • Methods
  • Basic OCC Keywords
  • Advanced OCC Keywords
  • Basic DFOCC Keywords
  • Advanced DFOCC Keywords
  • Conventional (Non-OO) Coupled-Cluster and Møller–Plesset Perturbation Theories
• PSIMRCC Implementation of Mk-MRCC Theory
  • A Simple Example
  • Orbital ordering and selection of the model space
• CI: Configuration Interaction
  • Basic DETCI Keywords
  • Spin Multiplicities of Higher Roots
  • Arbitrary Order Perturbation Theory
  • Arbitrary Order Coupled-Cluster Theory
• MCSCF: Multi-Configurational Self-Consistent-Field
  • Basic MCSCF Keywords
• SAPT: Symmetry-Adapted Perturbation Theory
  • The S² approximation and scaling
  • A First Example
  • Advanced example
  • SAPT0
  • SAPT(DFT)
  • Higher-Order SAPT
  • MP2 Natural Orbitals
  • Charge-Transfer in SAPT
  • Monomer-Centered Basis Computations
  • Computations with Mid-bonds
  • Interpreting SAPT Results
  • Spin-Flip SAPT
  • Higher-Order Exchange Terms without Single-Exchange Approximation
• F/I-SAPT: Functional Group and/or Intramolecular SAPT
  • F-SAPT: A Representative Example
  • Order-1 Visualization with PyMol
  • Difference F-SAPT Analysis
  • I-SAPT: A Representative Example
  • Cube File Visualization with PyMol
  • Adding Point Charges to F/I-SAPT Computations
  • F/I-SAPT Keywords
  • Additional Notes
• ADC: Ab Initio Polarization Propagator
  • Available ADC methods
  • Running ADC calculations
  • Interface to adcc
  • Built-in ADC(2) code
• Scalar relativistic Hamiltonians
  • A First Example
  • Basis sets options
  • Theory
• Geometry Optimization
  • Basic Keywords
  • Optimizing Minima
  • Hessian
  • Transition States, Reaction Paths, and Constrained Optimizations
  • Dealing with problematic optimizations
  • Direct manipulation of the optmization coordinates
  • Convergence Criteria
  • Interface to GeomeTRIC
  • Output
• Evaluation of One-Electron Properties — oeprop()
  • Basic Keywords
  • Properties evaluated on a grid
  • Minimal Basis Iterative Stockholder
• Vibrational and Thermochemical Analysis
  • Keywords
  • Examples
  • Output
• TDSCF: Time-dependent Hartree–Fock and density-functional theory
  • Introduction
  • Known limitations
  • Theory
  • Psithon keywords
  • PsiAPI usage
  • Plotting one-photon absorption and electronic circular dichroism spectra