Intermonomer interaction

The details of SAPT are beyond the scope of the present work. For our purposes it is enough to say that the fundamental components of the interaction energy are ordinarily expanded in terms of two perturbations the intermonomer interaction operator and the intramonomer electron correlation operator. Such a treatment provides us with fundamental components in the form of a double perturbation series, which should be judiciously limited to some low order, which produces a compromise between efficiency and accuracy. The most important corrections for two- and three-body terms in the interaction energy are described in Table 1. The SAPT corrections are directly related to the interaction energy evaluated by the supermolecular approach, Eq.(2), provided that many body perturbation theory (MBPT) is used [19,28]. Assignment of different perturbation and supermolecular energies is shown in Table 1. The power of this approach is its open-ended character. One can thoroughly analyse the role of individual corrections and evaluate them with carefully controlled effort and desired... 

Abstract The intermonomer interaction effect on electromagnetically induced transparency (BIT) in dipole-coupled dimer models with different orientations and intermonomer distances is investigated. The absorption properties are evaluated using the imaginary part of the dynamic polarizability a calculated by the quantum master equation method. It is found that BIT can be observed even in the dimer systems with near-degenerate excited states originating in an intermonomer interaction by adjusting the incident field frequency. 

Apparently, the reduced absorption by BIT shown as MINJm[a] is independent of the intermonomer distance both for the H- and the L-shaped dimer models, whereas MAX Jm[ot] gradually increases with the increase in R (the decrease in the intermonomer interaction) in case of the L-shaped dimer model. This result shows that BIT can be realized even when several states contribute to the optical response for the probe and coupling fields. This robustness of BIT is considered to originate in the frequency matching between the coupling field and the energy difference between the intermediate and metastable states. 

The importance of strong intermonomer interactions in building up the exciton is also reflected in the substantial delocalization of the excitonic wave function. Detailed results show that charge-transfer excitations for a distance of 4-5 residues contribute significantly to the calculated binding energy of the exciton, Eq. The Frenkel exciton (n = 0)... 

The dispersion nonadditivity Eib arises from the coupling of intermonomer pah-correlations in subsystems XY and YZ via the intermolecular interaction operator Vzx. This contribution can be expressed as a generalized Casimir-Polder formula,... 

The idea of correlating momentary multipoles stands behind the customary modeling of dispersion interaction in the form of a multipole expansion, including dipole-dipole (D-D), dipole-quadrupole (D-Q), quadrupole-quadrupole (Q-Q), and so on, terms. We owe the earliest variational treatments of this problem not only to Slater and Kirkwood [34], but also to Pauling and Beach [35], However, when the distance R decreases and reaches the Van der Waals minimum separation, the assumption that electrons of A and B never cross their trajectories in space becomes too crude. The calculation of the intermonomer electron... 

The basic equations that rule the mechanics of H-bonds are developed in this appendix. They have been already established in the appendix of Ch. 5 but take here a slightly different form that makes the role of the mass m of the H-atom more apparent, in view of predicting effects of an H/D substitution. The formation of an H-bond is the result of an electrostatic interaction between the electrons and the nuclei of two molecules X-H and Y. Molecules are quantum objects that are ruled by an Hamiltonian H that depends on the coordinates r of electrons, q of the H(D)-atom that establishes an H(D)-bond and Q that defines the relative positions of the two molecular components X-H and Y. r stands for aU coordinates of all electrons e. The relative coordinates q and Q of the nuclei are defined in Figure 2.1. Q stands for all three intermonomer coordinates Q, Qg and defined in this figure. The quantum description is necessary for this H-bond, because a classical description fails to describe any chemical bond. This Hamiltonian H writes ... 

In the asymptotic region, i.e. for large intermonomer separations R, the interaction energy is well described by the polarization terms alone. Moreover, at such distances one can make an additional approximation and represent the operator V in terms of its multipole expansion containing terms inversely proportional to powers of R. As R increases, the interaction energy will eventually be well represented by just the term with the lowest power of l//f. For polar dimers such as water, the lowest power equal to three is coming from the electrostatic interactions and the water dimer potential... 

The other very often considered nonadditive component is the induction energy. This component in its asymptotic form is the basis of the polarizable empirical potentials described in Section 33.3. For strongly polar systems, the second- and third-order nonadditive induction terms can indeed be expected to provide the largest nonadditive contribution except for small intermonomer separations [46] and to constitute the major part of the Hartree-Fock nonadditive contribution. The second-order terms have a very simple physical interpretation a multipole on system A induces multipole moments on B and C which interact with the permanent multipoles on C and B, respectively (see a more extensive discussion below). The second-order induction nonadditivity can be written as [85,86]... 

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