Symmetrized Rayleigh-Schrodinger perturbation theory

Cwiok T, Jeziorski B, Kolos W, Moszynski R, Szalewicz K (1992) On the convergence of the symmetrized Rayleigh-Schrodinger perturbation theory formolecular interaction energies. J Chem Phys 97 7555-7559... 

The application of perturbation theory to many-body interactions leads to pairwise-additive and non-pairwise-additive contributions. For example, in the case of neutral, spherically symmetric systems which are separated by distances such that the orbital overlap can be neglected, the first non-pairwise-additive term appears at third order of the Rayleigh-Schrodinger perturbation treatment and corresponds to the dispersion energy which results from the induced-dipole-induced-dipole-induced-dipole78 interaction... 

We start the presentation of our results with the Rayleigh-Schrodinger perturbation theory. The results presented in Table 1 show that for small interatomic distances the RS perturbation expansion converges to the energy of the mathematical ground state of the dimer. This state is a Pauli forbidden solution of the Schrodinger equation, completely symmetric un-... 

Clearly, standard Rayleigh-Schrodinger perturbation theory is not applicable and other perturbation methods have to be devised. Excellent surveys of the large and confusing variety of methods, usually called exchange perturbation theories , that have been developed are available [28, 65]. Here it is sufficient to note that the methods can be classified as either symmetric or symmetry-adapted . Symmetric methods start with antisymmetrized product functions in zeroth order and deal with the non-orthogonality problem in various ways. Symmetry-adapted methods start with non-antisymmetrized product functions and deal with the antisymmetry problem in some other way, such as antisymmetrization at each order of perturbation theory. 

EL-HAV = Eisenschitz, London-Hirschfelder, Amos, Van der Avoird FORS = fully optimized reaction space IMPT = intermolecular perturbation theory JS = Jeziorski-Kolos LCD = localized charge distribution MK = Morokuma-Ki-taura MS-MA = Murrell. Shaw-Musher, Amos RS-PT = Rayleigh-Schrodinger perturbation theory RVS = reduced variational space SA = symmetry-adapted perturbation theory SNOPT = symmetric non-orthogonal perturbation theory SRS = symmetrized Rayleigh-Schrddinger. 

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