26.1 Introduction

The local correlation program of MOLPRO can currently perform closed-shell MP2(D), MP3(D),
MP4(SDQ), CISD, QCISD, and CCSD calculations. So far, only MP2 is publicly available. Linear scaling versions of the other methods are still experimental and will be released later. Perturbative energy corrections for triple excitations are under development and will also be available in the near future. Note that you have to install the `local' module in order to use local correlation methods. If you want linear scaling, you also need the `direct' module.

References:

General, local CCSD:
$[1]$ C. Hampel and H.-J. Werner, Local Treatment of electron correlation in coupled cluster (CCSD) theory, J. Chem. Phys. 104, 6286 (1996).

Multipole treatment of distant pairs:
$[2]$ G. Hetzer, P. Pulay, H.-J. Werner, Multipole approximation of distant pair energies in local MP2 calculations, Chem. Phys. Lett. 290, 143 (1998).

Linear scaling local MP2:
$[3]$ M. Schütz, G. Hetzer and H.-J. Werner, Low-order scaling local electron correlation methods. I. Linear scaling local MP2, J. Chem. Phys. 111, 5691 (1999).

LMP2 Gradients and geometry optimization:
$[4]$ A. El Azhary, G. Rauhut, P. Pulay and H.-J. Werner, Analytical energy gradients for local second-order Møller-Plesset perturbation theory, J. Chem. Phys. 108, 5185 (1998).

LMP2 vibrational frequencies:
$[5]$ G. Rauhut, A. El Azhary, F. Eckert, U. Schumann and H.-J. Werner, Impact of Local Approximations on MP2 Vibrational Frequencies, Spectrochimica Acta 55, 651 (1999).

Intermolecular interactions and the BSSE problem:
$[6]$ M. Schütz, G. Rauhut and H.-J. Werner, Local Treatment of Electron Correlation in Molecular Clusters: Structures and Stabilities of (H$_2$O)$_n$, $n=2-4$, J. Phys. Chem. 102, 5997 (1998).

$[7]$ N. Runeberg, M. Schütz and H.-J. Werner, The aurophilic attraction as interpreted by local correlation methods, J. Chem. Phys. 110, 7210 (1999).