XMCQDPT (Extended Multi-Configuration Quasi-Degenerate Perturbation Theory) is the new approach to Multi-State Multi-Reference Petrurbation Theory developed by Dr. Alexander A. Granovsky of Firefly Proejct. XMCQDPT, sometimes referred also as MC-XQDPT, is the unique feature of Firefly and the PC GAMESS/Firefly.

XMCQDPT2 (XMCQDPT at second order of PT expansion, referred as MC-XQDPT2 in some older publications) is superior to MCQDPT2 and is aimed to completely replace MCQDPT2/DETPT2 calculations in the future. The detailed paper on XMCQDPT2 approach has been recently published in J. Chem. Phys.

Please cite XMCQDPT2 in your papers as follows:

A. A. Granovsky, J. Chem. Phys. **134**, 214113 (2011)

As this paper is the primary document on XMCQDPT2 theory, Firefly users are strongly encouraged to read it before performing any XMCQDPT2 calculations. The paper can be found in the Archives section of Firefly web site.

An input file for the XMCQDPT2 calculations is exactly the same as for the old-style MCQDPT2 ones, the only difference is that user must provide $XMCQDPT group rather than $MCQDPT one (note if both groups are given then MCQDPT calculation will be performed). All control keywords of the $XMCQDPT group are identical to that of the $MCQDPT group and hence all documentation relevant to MCQDPT2 is naturally applicable to XMCQDPT2 as well, including those documents and keywords which are specific to Firefly and PC GAMESS/Firefly e.g., documentation on large-scale calculations.

- PC GAMESS/Firefly input preprocessing sample
- 64-bit processing support
- Fast Matrix Diagonalization and Inversion
- Spherical Basis Functions
- Fast Two-electron Integral Code
- Additional comments on Two-electron Integral code selection
- Configuration Interaction Singles
- Time-dependent Hartree-Fock
- Time-dependent DFT
- CI and Multi-Configuration SCF
- Multi-Configuration Quasi-Degenerate Perturbation Theory
- P2P Parallel Mode Communication Interface, Dynamic Load Balancing, and large-scale MP2 Energy code
- New MP2 gradient code documentation
- PC GAMESS/Firefly' NBO code
- Cube Files
- Multicore, SMP and HTT support

Last updated: June 7, 2011