Double Rydberg anions, Rydberg radicals and micro-solvated cations with ammonium-water kernels.

Highly accurate electron-propagator and coupled-cluster methods are employed to predict the vertical electron attachment energies (VEAEs) of NH(HO) ( = 1-4) cationic clusters. The VEAEs decrease with increasing and the corresponding Dyson orbitals are diffused over peripheral, non-hydrogen bonded protons. Clusters formed from NH double Rydberg anions (DRAs) and stabilized by hydrogen bonding or electrostatic interactions are studied through calculations on NH(HO) complexes and are compared with more stable H(NH)(HO) isomers.

Complete-active-space extended Koopmans theorem method.

The complete-active-space (CAS) extended Koopmans theorem (EKT) method is defined as a special case of the EKT in which the reference state is a CAS configuration interaction (CI) expansion and the electron removal operator acts only on the active orbitals. With these restrictions, the EKT is equivalent to the CI procedure involving all hole-state configurations derived from the active space of the reference wavefunction and has properties analogous to those of the original Koopmans theorem. The equivalence is used to demonstrate in a transparent manner that the first ionization energy predicted by the EKT is in general not exact, i.

Electron binding energies and Dyson orbitals of OH clusters: Double Rydberg anions, Rydberg radicals, and micro-solvated hydronium cations.

Ab initio electron propagator methods are employed to predict the vertical electron attachment energies (VEAEs) of OH (HO) clusters. The VEAEs decrease with increasing n, and the corresponding Dyson orbitals are diffused over exterior, non-hydrogen bonded protons. Clusters formed from OH double Rydberg anions (DRAs) and stabilized by hydrogen bonding or electrostatic interactions between ions and polar molecules are studied through calculations on OH (HO) complexes and are compared with more stable H(HO) isomers.

Ionization Energies and Dyson Orbitals of the Iso-electronic SO, O, and S Molecules from Electron Propagator Calculations.

Adiabatic and vertical ionization energies corresponding to the X̃ , Ã , and B̃ final states of SO, O, and S have been calculated with a variety of electron-propagator and coupled-cluster methods. The BD-T1 electron-propagator method for vertical ionization energies and coupled-cluster adiabatic and zero-point corrections yield agreement with experiment to within 0.1 eV in all cases but one.

Excess electrons bound to HS trimer and tetramer clusters.

We have prepared the hydrogen sulfide trimer and tetramer anions, (HS) and (HS), measured their anion photoelectron spectra, and applied high-level quantum chemical calculations to interpret the results. The sharp peaks at low electron binding energies in their photoelectron spectra and their diffuse Dyson orbitals are evidence for them both being dipole-bound anions. While the dipole moments of the neutral (HS) and (HS) clusters are small, the excess electron induces structural distortions that enhance the charge-dipolar attraction and facilitate the binding of diffuse electrons.

Dyson Orbitals and Double Rydberg Anions: Methylated, Annulated, and Paramagnetic.

A double Rydberg anion (DRA) consists of a saturated, closed-shell, molecular cation and two electrons that occupy diffuse orbitals. Techniques of electron propagator theory (EPT) predict the existence and spectra of three new classes of DRAs. The first, with the formula NH(CH), has vertical electron detachment energies (VEDEs) that vary between 0.

Transition-metal solvated-electron precursors: diffuse and 3d electrons in V(NH).

Ground and excited electronic states of V(NH3)0,±6 complexes, investigated with ab initio electronic structure theory, consist of a V(NH3)62+ core with up to three electrons distributed over its periphery. This result extends the concept of super-atomic, solvated-electron precursors from alkali and alkaline-earth complexes to a transition metal. In the approximately octahedral ground state of V(NH3)6, three unpaired electrons occupy 3dxz, 3dyz and 3dxy (t2g) orbitals of vanadium and two electrons occupy a diffuse 1s outer orbital.

Molecules mimicking atoms: monomers and dimers of alkali metal solvated electron precursors.

Tetra-amino lithium and sodium complexes M(NH) (M = Li, Na) have one or two electrons that occupy diffuse orbitals distributed chiefly outside the M(NH) core. The lowest-energy 1s, 1p, and 1d orbitals follow Aufbau principles found earlier for beryllium tetra-ammonia complexes. Two ground state M(NH) complexes can bind covalently by coupling their 1s electrons into a σ-type molecular orbital.

Aufbau Rules for Solvated Electron Precursors: Be(NH) Complexes and Beyond.

Tetra-amino beryllium complexes and ions, Be(NH), have a tetrahedral Be(NH) core with one, two, or three outer electrons orbiting its periphery. Our calculations reveal a new class of molecular entities, solvated electron precursors, with Aufbau rules (1s, 1p, 1d, 2s, 1f, 2p, 2d) that differ from their familiar hydrogenic counterparts and resemble those of jellium or nuclear-shell models. The core's radial electrostatic potential suffices to reproduce the chief features of the ab initio results.

Ab initio electron propagator calculations of transverse conduction through DNA nucleotide bases in 1-nm nanopore corroborate third generation sequencing.

Background: The conduction properties of DNA molecule, particularly its transverse conductance (electron transfer through nucleotide bridges), represent a point of interest for DNA chemistry community, especially for DNA sequencing. However, there is no fully developed first-principles theory for molecular conductance and current that allows one to analyze the transverse flow of electrical charge through a nucleotide base.

Methods: We theoretically investigate the transverse electron transport through all four DNA nucleotide bases by implementing an unbiased ab initio theoretical approach, namely, the electron propagator theory.

New insights in the photochromic spiro-dihydroindolizine/betaine-system.

We have revisited the photochromic spiro-dihydroindolizine/betaine (DHI/B) system applying state-of-the-art density functional theory (DFT) calculations in combination with stationary and time-resolved absorption measurements. DHI/B-systems are becoming increasingly important as potential molecular machines, molecular switches, and photoswitchable electron-acceptors. The knowledge of the exact mechanisms of ring opening and closure, as well as of the geometries of DHI and betaine can provide critical information that will enable the design of better molecular machines and optical switches.

Removing electrons can increase the electron density: a computational study of negative Fukui functions.

Ab initio and density-functional theory calculations for a family of substituted acetylenes show that removing electrons from these molecules causes the electron density along the C-C bond to increase. This result contradicts the predictions of simple frontier molecular orbital theory, but it is easily explained using the nucleophilic Fukui function-provided that one is willing to allow for the Fukui function to be negative. Negative Fukui functions emerge as key indicators of redox-induced electron rearrangements, where oxidation of an entire molecule (acetylene) leads to reduction of a specific region of the molecule (along the bond axis, between the carbon atoms).

Base and phosphate electron detachment energies of deoxyribonucleotide anions.

Photoelectron spectra of deoxyribonucleotide anions are interpreted with ab initio, electron propagator calculations. Ground-state structures display hydrogen bonds which are not present in less stable minima that resemble Watson-Crick fragment geometries. For the adenosine and thymidine anions, there are two vertical electron detachment energies (VEDEs) within 0.