Analytical energy gradients for local second-order Moller-Plesset perturbation theory

by El Azhary, A.; Rauhut, G.; Pulay, P.; Werner, H. J.

Based on the orbital invariant formulation of Moller-Plesset (MP) perturbation theory, analytical energy gradients have been formulated and implemented for local second order MP (LMP2) calculations. The geometry-dependent truncation terms of the LMP2 energy have to be taken into account. This leads to a set of coupled-perturbed localization (CPL) equations which must be solved together with the coupled-perturbed Hartree-Fock (CPHF) equations. In analogy to the conventional non-local theory, the repeated solution of these equations for each degree of freedom can be avoided by using the z-vector method of Handy and Schaefer. Explicit equations are presented for the Pipek-Mezey localization. Test calculations on smaller organic molecules demonstrate that the local approximations introduce only minor changes of computed equilibrium structures.

Journal
Journal of Chemical Physics
Volume
108
Issue
13
Year
1998
Start Page
5185-5193
URL
https://dx.doi.org/10.1063/1.475955
ISBN/ISSN
1089-7690; 0021-9606
DOI
10.1063/1.475955