We present an interpretation of Fermi‐orbital descriptors (FODs) and argue that these descriptors carry chemical bonding information. We show that a bond order derived from these FODs agrees well with reference values, and highlight that optimized FOD positions used within the Fermi‐Löwdin orbital self‐interaction correction (FLO‐SIC) method correspond to expectations from Linnett's double‐quartet theory, which is an extension of Lewis theory. This observation is independent of the underlying exchange‐correlation functional, which is shown using the local spin density approximation, the Perdew–Burke–Ernzerhof generalized gradient approximation (GGA), and the strongly constrained and appropriately normed meta‐GGA. To make FOD positions generally accessible, we propose and discuss four independent methods for the generation of Fermi‐orbital descriptors, their implementation as well as their advantages and drawbacks. In particular, we introduce a re‐implementation of the electron force field, an approach based on the centers of mass of orbital densities, a Monte Carlo‐based algorithm, and a method based on Lewis‐like bonding information. All results are summarized with respect to future developments of FLO‐SIC and related methods. © 2019 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc.

We present pyflosic, an open-source, general-purpose python implementation of the Fermi–Löwdin orbital self-interaction correction (FLO-SIC), which is based on the python simulation of chemistry framework (pyscf) electronic structure and quantum chemistry code. Thanks to pyscf, pyflosic can be used with any kind of Gaussian-type basis set, various kinds of radial and angular quadrature grids, and all exchange-correlation functionals within the local density approximation, generalized-gradient approximation (GGA), and meta-GGA provided in the libxc and xcfun libraries. A central aspect of FLO-SIC is the Fermi-orbital descriptors, which are used to estimate the self-interaction correction. Importantly, they can be initialized automatically within pyflosic; they can also be optimized within pyflosic with an interface to the atomic simulation environment, a python library that provides a variety of powerful gradient-based algorithms for geometry optimization. Although pyflosic has already facilitated applications of FLO-SIC to chemical studies, it offers an excellent starting point for further developments in FLO-SIC approaches, thanks to its use of a high-level programming language and pronounced modularity.

A contribution to the production of zero‐defect materials is the development of carbon‐bonded alumina foam filters for removing nonmetallic inclusions from molten metals. Herein, such filters containing various mixtures of Carbores P, lactose, and tannin as binder are investigated by Raman spectroscopy. The filter samples differ in whether or not they are fired and whether or not n‐Si is added to them. Raman measurements are also performed on samples of the individual binder substances, which have been preannealed at temperatures up to 1400 °C. The variation of the sp2 carbon cluster sizes due to the heat treatment is estimated using the intensity ratio of the D and G bands as determined from these measurements. The conversion of the samples from hydrogen‐rich amorphous carbon systems to nanocrystalline graphite is observed. The results show no significant differences between the binders in regard to the material properties that can be studied with Raman spectroscopy.

Thermodynamic and kinetic information on the first two steps of gallic acid pyrolysis, a decarboxylation followed by a dehydrogenation, is obtained based on density functional theory and quantum chemistry. For the kinetics, transition states are identified with the help of the climbing image nudged elastic band method. Both reactions

Two measures of reactivity, the ionization potential and the standard enthalpy of formation, are evaluated for the AQUA20 molecular test set in this theoretical study, comparing results from density functional theory, wavefunction approaches, and methods from the field of self-interaction correction. All calculations are carried out for the gas phase and for an aqueous solution as simulated with the conductor-like screening model. For the gas phase, previously reported tendencies are confirmed. With the presented computational approach for the aqueous solution, the application of self-interaction correction improves the standard enthalpies of formation, but not the ionization potentials.

The aim of this study is the investigation of a technological synthesis of MgAlON, which is a prospective coating material on ceramic foam filters for the filtration of magnesium, aluminum, and other metal melts. Thermodynamic calculations are performed, and the synthesis is carried out at 1500 °C in nitrogen atmosphere using samples consisting of different fractions of Al2O3, MgO, and AlN as starting materials. The effect of the quantity of these components on the conversion degree of the educts is evaluated. Furthermore, the effect of the holding time at the synthesis temperature, as well as the composition points or regions showing the highest conversion degree, are determined. XRD analysis is performed to evaluate the phase fractions and lattice parameters of the spinel after the respective reaction, and the nitrogen content of selected samples is evaluated. Sessile drop tests using AlSi7Mg are performed at 950 °C on selected sintered samples, determining their wettability, and therefore, applicability of the material in light metal melt filtration.

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Lactose and tannin are eco‐friendly alternatives to commonly used binders for carbon‐bonded alumina filters that are applied in steel melt filtration. The investigation of binder pyrolysis is a contribution to understand the production process of these filters. In this work, lactose and the tannins gallic acid, ellagic acid, and tannic acid were investigated by Raman spectroscopy. The tannins were measured in situ in an argon‐filled heating chamber. The transformation of the tannin molecules to a system of amorphous disordered carbon could be observed in the Raman spectra. In addition, the condensed pyrolysis products of the tannins were measured and identified. The Raman spectra were supported by peak positions calculated with density functional theory.