NAME

       mp2 - Moller-Plesset Perburbation Theory

DESCRIPTION

       The  module  determines the second-order Moller-Plesset energy and one-particle density matrix (OPDM) for
       RHF, UHF, and ROHF (using semicanonical orbitals) references.  Frozen orbitals can be used when computing
       the energy but not the OPDM.

REFERENCES

       Original Moller-Plesset paper:

       1.     C. Moller and M. S. Plesset, "Note on an Approximation Treatment for Many-Electron Systems," Phys.
              Rev. 46, 618 (1934).

       Open-Shell Perturbation Theory

       1.     T. D. Crawford, H.  F.  Schaefer,  and  T.  J.  Lee,  "On  the  energy  invariance  of  open-shell
              perturbation theory with respect to unitary transformations of molecular orbitals," J. Chem. Phys.
              105, 1060 (1996).

       MP(2) Gradient Theory:

       1.     M.  Frisch,  M.  Head-Gordon, and J. Pople, "A Direct MP2 Gradient Method," Chem. Phys. Lett. 166,
              275 (1990).

       2.     I. Nielsen, "A new direct MP2 gradient algorithm  with  implementation  on  a  massively  parallel
              computer," Chem. Phys. Lett. 255, 210 (1996).

INPUT FORMAT

       Input for this program is read from the file input.dat. The following keywords are valid:

       WFN = string
              Specifies  the type of wave function desired. The only valid entry at the present is MP2. There is
              no default.

       REFERENCE = string
              Specifies the type of orbitals used for the single-determinant reference function.  Valid  entries
              include RHF, UHF, and ROHF.  There is no default.

       PRINT = integer
              Determines the verbosity of the output.  A value of 0 (the default) specifies minimal printing.

       CACHETYPE= string
              Selects  the priority type for maintaining the automatic memory cache used by the DPD codes.  (See
              libdpd.html for further details.)  A value of LOW (the default) selects a "low priority" scheme in
              which the deletion of items from the cache is based on pre-programmed priorities.  A value of  LRU
              selects a "least recently used" scheme in which the oldest item in the cache will be the first one
              deleted.

       CACHELEV= integer
              Selects  the  level of automatic cacheing desired in the storage of various amplitudes, integrals,
              and intermediates in the coupled cluster procedure.  A value of 0 retains no quantities in  cache,
              while  a  level  of  6  attempts  to  store  all  quantities  in  cache.   For  particularly large
              calculations, a value of 0 may help with certain types of memory  problems.   The  default  is  2,
              which  means  that  all four-index quantites with up to two virtual-orbital indices (e.g., <ij|ab>
              integrals) may be held in the cache.

       OPDM = boolean
              If TRUE calculate the one-particle density matrix  and  make  OPDM_WRITE  default  to  TRUE.   The
              default value of OPDM is FALSE.

       OPDM_WRITE = boolean
              Flag for whether or not to write the one-particle density matrix to disk.

       OPDM_PRINT = boolean
              Flag for whether or not to print the one-particle density matrix.

                                                 10 August, 2003                                          mp2(1)