Firefly Functionality and Capabilities

Similarities with GAMESS (US)

Firefly shares lots of functionality with the GAMESS (US). All the functionality of October 25, 1999 release of GAMESS (US) is supported. Many additional features added to GAMESS (US) since 1999 are supported as well. Ab initio SCF wavefunctions for RHF, UHF, ROHF, GVB and MCSCF cases are available. Correlation corrections include configuration interaction (CI) and Moller-Plesset (MP) perturbation theory. Excited electronic states can be described via the configuration interaction singles (CIS), RPA, and TDDFT approximations. Effective core potentials and a variety of density functional (DFT) approaches are available. Geometry optimization can be performed with analytical gradients at the HF, MP2, CI, DFT, TDHF, and TDDFT levels. Analytical Hessian can be computed at RHF, ROHF and GVB wavefunctions while numerical Hessians are available for all methods that support analytic gradients.


Firefly extends functionality of the GAMESS (US) program by providing very fast Moller-Plesset second, third and fourth order correlation corrections based on the self-consistent electron pairs (SCEP) theory. It allows separate evaluation of singlet and triplet pair contributions to MP2, MP3, and MP4(D) energies. The DFT code in the Firefly is completely different and is much faster than in the GAMESS (US) and the two programs support different density functionals. Firefly includes support of RPA (TDHF) and TDDFT for excited states.

Firefly lacks some features that have been implemented in the recent versions of GAMESS (US). For example, Firefly currently does not support coupled cluster methods and the fragment molecular orbitals. Both Firefly and GAMESS (US) lack support for h and higher angular momentum basis functions.

Summary Table

The table below summarizes the current main capabilities of Firefly:

       Wavefunction        RHF   UHF   ROHF   GVB   MCSCF
  Semiempirical SCF         dm    dm    dm     dm     -
  SCF energy               cdp   cdp   cdp    cdp    cdp
  SCF gradient             cdp   cdp   cdp    cdp    cdp 
  SCF Analytical Hessian   cdp*   -    cdp*   cdp*    -
  DFT energy               cdp   cdp   cdp     -      -
  DFT gradient             cdp   cdp   cdp     -      -
  CIS energy               cdp    -     -      -      -
  CIS gradient             cdp    -     -      -      -
  RPA energy               cdp    -     -      -      -
  RPA gradient             cdp    -     -      -      -
  TDDFT energy             cdp    -     -      -      -
  TDDFT gradient           cdp    -     -      -      -
  MP2 energy               cdp   cdp   cdp     -     cdmp
  MP2 gradient             cdp    -     -      -      -
  RI-MP2 energy            cdp   cdp   cdp     -     cdmp
  MP3 energy               cdm    -     -      -      -
  MP4 energy               cdmp*  -     -      -      -
  CI  energy               cdp    -    cdp    cdp    cdp
  CI  gradient             cd*    -     -      -      -

  Notes: c - conventional
         d - direct/semidirect
         m - multithreaded
         p - parallel
         * - additional notes: 1. CI gradients and  SCF Analytical Hessians are
                                  programmed for SPD basis sets only 
                                  (note CIS gradients are available for any 
                                  supported basis sets)
                               2. For GVB, SCF Analytical Hessians are available only for 
                                  selected subset of possible GVB-type wavefunctions 
                               3. MP4(SDQ)  code is multithreaded but not parallel while 
                                  MP4(SDTQ) code is both multithreaded and parallel for (T) part