Improving convergence of experimental and computed vertical ionization energies using the ionization potential equation-of-motion coupled-cluster with singles and doubles method

Comparison of statistically evaluated experimental vertical ionization energies (IEs) for 53 medium-sized molecules (6-34 atoms) with ionization potential equation-of-motion coupled-cluster with singles and doubles (IP-EOMCCSD) computations shows that discrepancies between computed and experimental results can be accounted for with a combination of experimental and theoretical contributions. Discrepancies can be minimized by extrapolating computations to the complete basis set limit and correcting for vibrational zero-point energy (ZPE) while comparing with experimental IEs calculated as the intensity-weighted mean band position to account for band asymmetries. This procedure reduced the average discrepancy for ethylene, (E)-2-butene, 2,5-dihydrofuran, and pyrrole from 0.25 to 0.05 eV. Agreement between reported vertical IEs and computations without either making adjustments as described in this paper or using complete simulation of the ionization spectrum should be considered fortuitous. The comparisons made in this work show that estimates of vertical and adiabatic IE made using IP-EOMCCSD extrapolated to the complete basis set limit and corrected for vibrational ZPE can be used with reasonable confidence when experimental values are not available.     

An explicit mapping between the frequency domain and the time domain representations of non-linear systems

Explicit expressions are presented that describe the input–output behaviour of a non-linear system in both the frequency and the time domain. The expressions are based on a set of coefficients that do not depend on the input to the system and are universal for a given system. The anharmonic oscillator is chosen as an example and is discussed for different choices of its physical parameters. It is shown that the typical approach for the determination of the Volterra Series representation is not valid for the important case when the non-linear system exhibits oscillatory behaviour and the input has a pole at the origin (in the frequency domain), e.g. the unit-step function. For this case, resonant effects arise and the analysis requires additional care.     

Asymptotic solvers for ordinary differential equations with multiple frequencies

We construct asymptotic expansions for ordinary differential equations with highly oscillatory forcing terms,focusing on the case of multiple,non-commensurate frequencies.We derive an asymptotic expansion in inverse powers of the oscillatory parameter and use its truncation as an exceedingly effective means to discretize the differential equation in question.Numerical examples illustrate the effectiveness of the method.     

An application of infrared analysis to determine the mineralogical phases formation in fluxes for thin slab casting of steel

The Fourier Transformed Infrared (FTIR) spectra analysis of two fluxes used in the thin slab casting process of steel were carried out in order to identify the mineralogical species present in fluxes as received and after a heat treatment to 1573 K and further solidification at two different cooling velocities. Fluxes as received show the presence of wollastonite (CaO·SiO₂) and a sodium carbonate (Na₂CO₃) as the main components; after the heat treatment, there was almost a whole transformation from the original compounds to cuspidine (3CaO·2SiO₂·CaF₂) and nepheline (Na₂O·Al₂O₃·2SiO₂) phases. These results were confirmed by X-ray powder diffraction (XRD) to the slowly cooling velocity. The FTIR technique is proposed as a useful and complementary technique to X-ray diffraction to study the structure of commercial fluxes for thin slab casting.     

Iridium-catalyzed, substrate-directed C-H borylation reactions of benzylic amines

The iridium-catalyzed arene C-H borylation reaction of benzylic amines has been developed, which inverts the typical steric-controlled product distribution to provide ortho-substituted boronate esters. Picolylamine was found to be an ideal ligand to replace 4,4'-di-tert-butylbipyridine to induce the directing effect. Preliminary experiments are consistent with a mechanism involving dissociation of one amine of the hemilabile diamine ligand.