Potential energy surfaces many-body perturbation

A second generalization of the many-body perturbation theory, which would certainly be useful in the calculation of potential energy curves and surfaces, would be to use a reference function constructed from non-orthogonal orbitals. 

Later work evaluated the two-dimensional potential energy surface using various correlation treatments including many-body perturbation theory and coupled cluster techniques Evaluation of the vibrational spectrum was explicitly anharmonic in nature, mak-... 

In previous publications we have described the application of the linked-diagram-based methods, many-body perturbation theory and coupled-cluster double-excitation theory, for the computation of potential energy surfaces, electronic excitation energies, and molecular properties. Here we report details of potential energy surface features for two species commonly found in flames formyl radical, HCO, and hydrogen nitroxide, HNO. In particular, we... 

Many-body perturbation theory (MBPT) " and coup led-cluster methods (CCM) are relatively new techniques, compared to configuration interaction (Cl), for the determination of electron correlation effects on potential energy surfaces. 1 -2 5 mBPT/CCM... 

As a second model potential we shall briefly discuss the PES for the water dimer. Analytical potentials developed from ab initio calculations have been available since the mid seventies, when Clementi and collaborators proposed their MCY potential [49], More recent calculations by dementi s group led to the development of the NCC surface, which also included many-body induction effects (see below) [50]. Both potentials were fitted to the total energy and therefore their individual energy components are not faithfully represented. For the purposes of the present discussion we will focus on another ab initio potential, which was designed primarily with the interaction energy components in mind by Millot and Stone [51]. This PES was obtained by applying the same philosophy as in the case of ArCC>2, i.e., both the template and calibration originate from the quantum chemical calculations, and are rooted in the perturbation theory of intermolecular forces. 

Recently, a new theoretical method of calculating potential energy and dipole/polarizability surfaces for van der Waals molecules based on symmetry-adapted perturbation theory (sapt) of intermolecular forces (12)— (15) has been developed (16)-(24). In this method, referred to as many-body symmetry-adapted perturbation theory, all physically important contributions to the potential and the interaction-induced properties, such as electrostatics, exchange, induction, and dispersion are identified and computed separately. By making a perturbation expansion in the intermolecular interaction as well as in the intramolecular electronic correlation, it is possible to sum the correlation contributions to the different physical... 

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