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)