Spatial partitioning of the molecular wave function: Reexamination of the bond‐charge model of covalent binding

Abstract

ABSTRACT:Owing to the complexity of many-body quantum interactions, theoretical problems in chemistry almost always necessitate numerical methods of solution. In turn, and somewhat paradoxically, this reliance on computation often precipitates a need for approximate models that can provide a conceptual framework for the interpretation of the accurate numerical solutions. In this report, we reexamine and improve upon the simple bond-charge (SBC) model of Parr and Borkman with the express purpose of examining its role as a suitable intuitive model for bonding energetics. We first discuss the role of spatial partitioning in the SBC model and the molecular-structure approximations that are implicit within the model. We then develop an improved version of the model by including electrostatic repulsion between shared electron pairs; we refer to this enhanced version as a semiempirical charge-cloud (SCC) model. Applying the SCC model to a broad range of diatomics, we find that it is able to predict dissociation energies on a par with simple variational calculations. As an illustrative application of the SCC model, we use it to estimate unknown dissociation energies and rotational constants for a number of alkali dimers.

Collisional Control of Ground State Polar Molecules and Universal Dipolar Scattering

“…2 we have plotted T as a function of ξ for 87 Rb 41 K (black x), fermionic 87 Rb 40 K (black +), NaCs (brown squares), and RbCs (red diamonds), which is the data in Fig. 1 (a) [22]. A line proportional to ξ is shown as a blue line with triangles.…”

“…We have calculated of RbCs [22] as a function of energy for many different electric fields and with different values of a s . Figure 1(a) shows the total RbCs cross section versus energy at electric fields of 0.5 (black), 1 (red), 2 (blue), and 5 (brown) E 0 .…”

“…To begin the analysis we illustrate the influence of the short range interaction as the electric field is varied. We have calculated σ of RbCs [22] as a function of energy for many different electric fields and with different values of a s . Figure 1 (a) shows the total RbCs cross section versus energy at electric fields of 0.5 (black), 1 (red), 2 (blue), 3 (green), and 5 (brown) E 0 .…”

Semiempirical theory of Carver rates in alkali/noble-gas systems

“…3,4 Aside from the fact that these mechanisms elucidate the nonelectrostatic interactions that exist between atoms, which are often dwarfed by the Coulomb forces of covalent binding, 5 understanding the mechanisms of alkali ground state relaxation has technological implications for atomic clocks 6,7 and magnetometers. 3,4 Aside from the fact that these mechanisms elucidate the nonelectrostatic interactions that exist between atoms, which are often dwarfed by the Coulomb forces of covalent binding, 5 understanding the mechanisms of alkali ground state relaxation has technological implications for atomic clocks 6,7 and magnetometers.…”

Description of covalent bond in terms of generalized charges: potential and dissociation energy of homonuclear compound

“…In the absence of analytic expressions, each particular case requires a separate study [10,11]. The complexity and low accuracy of these methods pose the necessity of using empirical expressions for the potentials of atom-atom interactions, which reduces the quality of the theory of chemical bonds [12][13][14].…”