Temporary Anion States of Ethene Interacting with Single Molecules of Methane, Ethane, and Water

Abstract

When an excess electron is added into the π* orbital of ethene, the resulting anion decays by electron autodetachment; that is, it represents an electronic state referred to as a temporary anion or resonance state. Here, the influence of a cluster environment on the energy and lifetime of this state is investigated. The clusters considered are ethene···CH, ethene···CH, and ethene···HO. Most of these clusters are systematically constructed so that the solvent interacts with the π system in a specific way, and are thus by construction not minima with respect to all intermolecular degrees of freedom. However, for water, in addition, a minimal energy structure is examined. Systematic variation of the solvent and solvation geometry allows us to identify trends regarding effects due to polarizability, excluded volume, and polarity of the solvent molecules. The resonance parameters of ethene and all temporary cluster anions are computed with the symmetry-adapted cluster-configuration interaction electronic structure method in combination with a complex absorbing potential. This method is well-established for small to intermediate sized molecules. In addition to the study of the solvation effects themselves, the question of how many basis functions are needed on the closed-shell solvating unit is examined.

The Clusterization Technique: A Systematic Search for the Resonance Energies Obtained via Padé

“…Such an approach holds an obvious advantage since it is based on Hermitian formalism, in which the Hamiltonian is real. These methods are based on stabilization techniques − and are usually followed by an analytical continuation from the real to complex space. ,,,− These methods differ in the way the analytical continuation is carry out or by the way the stabilization is obtained. ,, RVP, which is in the focus of this paper, is an analytical continuation approach, and herein we establish a practical tool for identifying the resonance energies within this approach.…”

“…12,13,24,54−56 These methods differ in the way the analytical continuation is carry out or by the way the stabilization is obtained. 24,54,55 RVP, which is in the focus of this paper, is an analytical continuation approach, and herein we establish a practical tool for identifying the resonance energies within this approach.…”

Irradiation of Plutonium Tributyl Phosphate Complexes by Ionizing Alpha Particles: A Computational Study

“…The application of complex boundary conditions was extended to the Schrödinger equation, , and then to the time-dependent Schrödinger equation applied on molecular systems to deal with diffuse reactions such as collisions between atoms. , In this context, CAP have been introduced as an alternative to mask functions . By adding a complex component to the system’s Hamiltonian, the electron density is gradually absorbed beyond a threshold distance. ,,− CAPs have been shown to be very effective when coupled with various electronic structures methods such as multiconfigurational methods, − coupled-cluster methods, − Lanczos-based approach, and Electron Attachment Algebraic-Diagrammatic Construction (EA-ADC) method in the study of metastable resonance states for anionic molecular systems. Its applications are extended in the generation of high harmonic generation (HHG) spectra with RT-TD-DFT, other Time-Dependent methods (TD-CIS, TD-SE, TD-CI), − or in non-Hermitian exceptional point (EPs) degeneracies .…”

Combination of a Voronoi-Type Complex Absorbing Potential with the XMS-CASPT2 Method and Pilot Applications

“…For small compact molecules, Voronoi CAPs offer no great advantages over box-CAPs, indeed, the need to compute the Voronoi matrix elements numerically represents a major disadvantage in these cases. However, Voronoi CAPs show the same symmetry as the Hamiltonian and, more importantly, adapt to changes in molecular geometry far more flexibly than box-CAPs. − As an extreme example, consider the following solvation model: a temporary anion in the coordinate origin surrounded by six solvent molecules at a distance R from the origin centered on the positive and negative Cartesian axes. If R is increased from a small value representing solvation to a large value representing the unsolvated molecule, the cutoff parameter of a box-CAP needs to be increased accordingly so as to include the solvent molecules in the CAP-box, and converging the basis set will become increasingly difficult if not impossible.…”