First-order symmetry-adapted perturbation theory for multiplet splittings

Charge Transfer from Regularized Symmetry-Adapted Perturbation Theory.

The charge-transfer (CT) together with the polarization energy appears at second and higher orders in symmetry-adapted perturbation theory (SAPT). At present there is no theoretically compelling way of isolating the charge-transfer energy that is simultaneously basis-set independent and applicable for arbitrary intermolecular separation. We argue that the charge-transfer can be interpreted as a...

Breakdown of the single-exchange approximation in third-order symmetry-adapted perturbation theory.

We report third-order symmetry-adapted perturbation theory (SAPT) calculations for several dimers whose intermolecular interactions are dominated by induction. We demonstrate that the single-exchange approximation (SEA) employed to derive the third-order exchange-induction correction (E(exch-ind)((30))) fails to quench the attractive nature of the third-order induction (E(ind)((30))), leading t...

SAPT A Program for Many Body Symmetry Adapted Perturbation Theory Calculations of Intermolecular Interaction Energies

First-order quantum perturbation theory and Colombeau generalized functions

The electromagnetic scattering of a spin-0 charged particle off a fixed center is calculated in first-order quantum perturbation theory. This implies evaluating the square of a ‘Dirac delta-function,’ an operation that is not defined in Schwartz distribution theory, and which in elementary text-books is dealt with according to ‘Fermi’s golden rule.’ In this paper these conventional calculations...

First Order Eigenvalue Perturbation Theory and the Newton Diagram

First order perturbation theory for eigenvalues of arbitrary matrices is systematically developed in all its generality with the aid of the Newton diagram, an elementary geometric construction first proposed by Isaac Newton. In its simplest form, a square matrix A with known Jordan canonical form is linearly perturbed to A(ε) = A+ ε B for an arbitrary perturbation matrix B, and one is intereste...