Energies, polarizabilities, and forces of interacting molecules at long or intermediate range
Collision-induced molecular phenomena are widely researched subjects. In complement with other research, deriving new results to understand the nature and effects of the interaction between molecules at long or intermediate range in the main goal of this thesis. By applying Rayleigh-Schroedinger perturbation theory, we have obtained the molecular interaction energy to second order in terms of nonlocal polarizability densities. The derivation also includes the effects of an applied field. The nonlocal polarizability density {alpha}(r; r`, {omega}) plays a central role in this research. the polarizability density is a linear-response tensor that determines the electronic polarization induced at point r in a molecule, by an external electric field of frequency {omega}, acting at r`. When a nuclear position in the molecules shifts infinitesimally, we find that the change in {alpha}(r, r`, {omega}) is connected to the same hyperpolarizability {beta}{sub alpha}{sub beta}{sub gamma}(r; r`, {omega},O) that describes the electronic charge distribution`s response to external fields, i.e.: {partial_derivative}{alpha}{sub beta}{sub gamma}({omega})/{partial_derivative}R{sup I}{sub alpha}. Due to establishment of the relationships between {partial_derivative}{alpha}{sub beta}{sub gamma}/{partial_derivative}R{sup I}{sub alpha} and {beta}{sub beta}{sub gamma}{sub delta}, we have obtained new analytical results for the forces acting on nuclei in a molecule. For the first time, we have proven the equivalence of forces from interaction energy calculations and those obtained via the Hellmann-Feynman theorem, order by order. We are also able to separate forces on nuclei in one of the interacting molecules (A) into those due to its `own` electrons vs. forces due to the charge distribution of the collision partner B.
- Research Organization:
- Michigan State Univ., East Lansing, MI (United States)
- OSTI ID:
- 111295
- Country of Publication:
- United States
- Language:
- English
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