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.