MOLPRO

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Introduction to MOLPRO
MOLPRO is a complete system of ab initio programs for molecular electronic structure calculations,
designed and maintained by H.-J. Werner and P. J. Knowles, and containing contributions
from a number of other authors. As distinct from other commonly used quantum chemistry
packages, the emphasis is on highly accurate computations, with extensive treatment of the
electron correlation problem through the multiconfiguration-reference CI, coupled cluster and
associated methods. The recently developed explicitly correlated coupled-cluster methods yield
CCSD(T) results with near basis set limit accuracy already with double−ζ or triple−ζ basis
sets, thus reducing the computational effort for calculations of this quality by two orders of
magnitude. Using local electron correlation methods, which significantly reduce the increase
of the computational cost with molecular size, accurate ab initio calculations can be performed
for much larger molecules than with most other programs. These methods have recently been
augmented by explicitly correlated terms, which strongly reduce both the basis set truncation
errors and the errors of the local approximations.
The heart of the program consists of the multiconfiguration SCF, multireference CI, and coupledcluster
routines, and these are accompanied by a full set of supporting features. The package
comprises
• Integral generation for generally contracted symmetry adapted gaussian basis functions
(spd f ghi). There are two programs with identical functionality: the preferred code is
SEWARD (R. Lindh) which is the best on most machines; ARGOS (R. M. Pitzer) is available
as an alternative, and in some cases is optimum for small memory scalar machines.
Also two different gradient integral codes, namely CADPAC (R. Amos) and ALASKA (R.
Lindh) are available. Only the latter allows the use of generally contracted symmetry
adapted gaussian basis functions.
• Effective Core Potentials (contributions from H. Stoll).
• Many one-electron properties.
• Some two-electron properties, e.g. L 2 x, L 2 y, L 2 z , L x L y etc..
• Closed-shell and open-shell (spin restricted and unrestricted) self consistent field.
• Density-functional theory in the Kohn-Sham framework with various gradient corrected
exchange and correlation potentials.
• Multiconfiguration self consistent field. This is the quadratically convergent MCSCF
procedure described in J. Chem. Phys. 82 (1985) 5053. The program can optimize a
weighted energy average of several states, and is capable of treating both completely general
configuration expansions and also long CASSCF expansions as described in Chem.
Phys. Letters 115 (1985) 259.
• Multireference CI. As well as the usual single reference function approaches (MP2, SDCI,
CEPA), this module implements the internally contracted multireference CI method as
described in J. Chem. Phys. 89 (1988) 5803 and Chem. Phys. Lett. 145 (1988) 514. Non
variational variants (e.g. MR-ACPF), as described in Theor. Chim. Acta 78 (1990) 175,
are also available. Electronically excited states can be computed as described in Theor.
Chim. Acta, 84 95 (1992).
• Multireference second-order and third-order perturbation theory (MRPT2, CASPT2, MRPT3)
as described in Mol. Phys. 89, 645 (1996) and J. Chem. Phys. 112, 5546 (2000).