mp2 - Moller-Plesset Perburbation Theory

       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.

       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)

       mp2 - Moller-Plesset Perburbation Theory

       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).