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Three-body bonds

Observe the presence, in Fig. 17, of three-body bonds [26], as they are named, common in planar clusters. They are characterized by peaks of charge inside triangles delimited by 3 atoms. The C2v Li5" charge density is more delocalized,... [Pg.401]

For the lithium clusters, we have seen that the Pauling s structures can have the highest weights in the VB wave function, e.g. the C2v Li4" and C2v Li5 clusters. The structures are certainly very important when three-body bonds are present. According to our results, a VB description of the anionic or neutral lithium clusters without the Pauling s structures would be incomplete or would result in a less compact wave function. [Pg.413]

The first term represents the long range electrostatic interactions, the second term is a two body short range interaction while the last term is the three body bond bending potential. [Pg.146]

The computational effort is significantly increased if three-body terms are included in the model. Even with a simple pairwise model, the non-bonded interactions usually require by far the greatest amount of computational effort. The number of bond, angle and torsional terms increases approximately with the number of atoms (N) in the system, but the number of non-bonded interactions increases with N. There are N(N —l)/2 distinct pairs of... [Pg.231]

Three-body and higher terms are sometimes incorporated into solid-state potentials. The Axilrod-Teller term is the most obvious way to achieve this. For systems such as the alkali halides this makes a small contribution to the total energy. Other approaches involve the use of terms equivalent to the harmonic angle-bending terms in valence force fields these have the advantage of simplicity but, as we have already discussed, are only really appropriate for small deviations from the equilibrium bond angle. Nevertheless, it can make a significant difference to the quality of the results in some cases. [Pg.257]

Table IV. Comparison of stability and structure of Ain clusters between ab initio and parameterized interaction results with two- and three-body terms (2+3-b) as well as using only the two-body (2-b) interaction. Binding energies (Dc in eV) per atom, and bond distances (rg in ao) are given... Table IV. Comparison of stability and structure of Ain clusters between ab initio and parameterized interaction results with two- and three-body terms (2+3-b) as well as using only the two-body (2-b) interaction. Binding energies (Dc in eV) per atom, and bond distances (rg in ao) are given...
It was noted in the early study by Pankove et al. (1985) that the hydrogen vibrational frequency appropriate to the H—B pair was in the range consistent with a hydrogen bonded to a silicon but was in fact somewhat smaller than that expected for an isolated hydrogen connected to a single silicon. Generally, if an atom becomes more confined, the frequency is expected to increase. It was suggested that the frequency reduction was due to a three-body effect well known in molecules. [Pg.547]

M. Quack, J. Stohner, and M. A. Suhm, Analytical three body interaction potentials and hydrogen bond dynamics of hydrogen fluoride aggregates (HF)n, n>3.J. Mol. Struct. 599, 381 425 (2001). [Pg.45]

One formalism which has been extensively used with classical trajectory methods to study gas-phase reactions has been the London-Eyring-Polanyi-Sato (LEPS) method . This is a semiempirical technique for generating potential energy surfaces which incorporates two-body interactions into a valence bond scheme. The combination of interactions for diatomic molecules in this formalism results in a many-body potential which displays correct asymptotic behavior, and which contains barriers for reaction. For the case of a diatomic molecule reacting with a surface, the surface is treated as one body of a three-body reaction, and so the two-body terms are composed of two atom-surface interactions and a gas-phase atom-atom potential. The LEPS formalism then introduces adjustable potential energy barriers into molecule-surface reactions. [Pg.306]

Reaction 2-2 is actually a three-body process, in that another molecule (Af), usually nitrogen or oxygen, is necessary to carry off the energy released in the newly formed bond. These two reactions then form a mechanism for ozone formation in the atmosphere. They would not be complete without the additional reaction,... [Pg.18]

The H7+ molecule-ion, which consists of two protons and one electron, represents an even simpler case of a covalent bond, in which only one electron is shared between the two nuclei. Even so, it represents a quantum mechanical three-body problem, which means that solutions of the wave equation must be obtained by iterative methods. The molecular orbitals derived from the combination of two Is atomic orbitals serve to describe the electronic configurations of the four species H2+, H2, He2+ and He2. [Pg.36]


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Three body interaction, hydrogen bonds

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