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GAMESS

The General Atomic and Molecular Electronic Structure System (GAMESS) is a comprehensive quantum chemistry software package for performing ab initio, density functional, and multireference electronic structure calculations.

GAMESS provides a wide range of computational methods for studying

  • Ground-state electronic structure
  • Excited electronic states
  • Potential energy surfaces
  • Spectroscopic properties
  • Reaction mechanisms
  • Nonadiabatic dynamics
  • Magnetic properties

It supports methods ranging from introductory Hartree–Fock calculations to advanced multiconfigurational approaches such as CASSCF, XMCQDPT, and MCSCF diabatization, making it one of the most versatile electronic structure packages available for theoretical chemistry.

Official Resources

  • GAMESS Manual

    Official documentation describing all input groups, keywords, and computational methods.

    Open Manual

  • Official Website

    Download GAMESS, view release notes, and access additional documentation.

    Visit Website

Recommended Learning Workflow

If you are new to electronic structure theory, we recommend studying the tutorials in the following order.

┌───────┐
│  RHF  │
└───┬───┘
    ▼
┌───────┐
│  CIS  │
└───┬───┘
    ▼
┌────────┐
│ CASSCF │
└───┬────┘
    ▼
┌─────────┐
│ XMCQDPT │
└───┬─────┘
    ▼
┌──────────────┐
│ Diabatization│
└───┬──────────┘
    ▼
┌──────────────┐
│ PES Analysis │
└───┬──────────┘
    ▼
┌──────────────┐
│ Dynamics     │
└──────────────┘

Each tutorial builds upon the previous one. For example,

  • RHF introduces molecular orbitals and the Self-Consistent Field method.
  • CIS extends RHF to electronically excited states.
  • CASSCF introduces multiconfigurational wavefunctions and active spaces.
  • XMCQDPT incorporates dynamic electron correlation.
  • Diabatization constructs diabatic representations for photochemical applications.
  • Potential Energy Surface Distortion explores molecular distortions and excited-state pathways.

Tutorials

  • Restricted Hartree–Fock (RHF)

    Learn the foundations of electronic structure theory, molecular orbitals, and Self-Consistent Field calculations.

    Explore RHF

  • Configuration Interaction Singles (CIS)

    Study electronically excited states, orbital transitions, and active-space selection.

    Explore CIS

  • Complete Active Space SCF (CASSCF)

    Learn multiconfigurational electronic structure theory for strongly correlated systems.

    Explore CASSCF

  • Extended Multi-Configurational Quasi-Degenrate Perturbation Theory (XMCQDPT)

    Dynamic correlation for multiconfigurational wavefunctions.

    Explore XMCQDPT

Upcoming Tutorials

The following tutorials will be added in future releases.

  • Diabatization

    Construction of diabatic Hamiltonians for excited-state dynamics.

  • Potential Energy Surface Distortion

    Exploring reaction coordinates and molecular distortions.

  • Spin–Orbit Coupling

    Calculation of spin–orbit matrix elements and state interactions.

  • Optical Properties

    Oscillator strengths, transition dipoles, and UV–Visible spectra.

  • Nonadiabatic Dynamics

    Surface hopping, wavepacket dynamics, and excited-state relaxation.