Provided by: psi3_3.4.0-6_amd64 
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)