Fulgide Derivatives as Photo-Switchable Coatings for Cathodes of Lithium Ion Batteries - A DFT study.

Photo-switchable coatings for lithium ion batteries (LIB) can offer the possibility to control the diffusion processes from the electrode materials to the electrolyte and thus, for example, reducing the energy loss in the fully charged state. Fulgide derivatives, as known photo-switches, are investigated concerning their use as coating for vanadium pentoxide, a potential cathode material for LIB. With the help of Density Functional Theory calculations, two fulgide derivatives are characterized with respect to their photophysics, their aggregation behaviour on the cathode material and the ability to form self-assembled monolayers (SAM). Furthermore, the two states of the photo-switchable coating are tested with respect to lithium diffusion from the cathode material, passing the SAM and entering the electrolyte. We found a difference for the energy barriers depending on the state of the photo-switch, preferring its closed form. This behaviour can be used to prevent the loss of charge in batteries of portable devices.

Effect of Substitutional Metallic Impurities on the Optical Absorption Properties of TiO2.

(TiO2) is both a natural and artificial compound that is transparent under visible and near-infrared light. However, it could be prepared with other metals, substituting for Ti, thus changing its properties. In this article, we present density functional theory calculations for Ti(1-x)AxO2, where A stands for any of the eight following neutral substitutional impurities, Fe, Ni, Co, Pd, Pt, Cu, Ag and Au, based on the rutile structure of pristine TiO2. We use a fully unconstrained version of the density functional method with generalized gradient approximation plus the U exchange and correlation, as implemented in the Quantum Espresso free distribution. Within the limitations of a finite-size cell approximation, we report the band structure, energy gaps and absorption spectrum for all these cases. Rather than stressing precise values, we report on two general features: the location of the impurity levels and the general trends of the optical properties in the eight different systems. Our results show that all these substitutional atoms lead to the presence of electronic levels within the pristine gap, and that all of them produce absorptions in the visible and near-infrared ranges of electromagnetic radiation. Such results make these systems interesting for the fabrication of solar cells. Considering the variety of results, Ni and Ag are apparently the most promising substitutional impurities with which to achieve better performance in capturing the solar radiation on the planet's surface.

Optoelectronic Response to the Fluor Ion Bond on 4-(4,4,5,5-Tetramethyl-1,3,2-dioxoborolan-2-yl)benzaldehyde.

Boronate esters are a class of compounds containing a boron atom bonded to two oxygen atoms in an ester group, often being used as precursors in the synthesis of other materials. The characterization of the structure and properties of esters is usually carried out by UV-visible, infrared, and nuclear magnetic resonance (NMR) spectroscopic techniques. With the aim to better understand our experimental data, in this article, the density functional theory (DFT) is used to analyze the UV-visible and infrared spectra, as well as the isotropic shielding and chemical shifts of the hydrogen atoms 1H, carbon 13C and boron 11B in the compound 4-(4,4,5,5-tetramethyl-1,3,2-dioxoborolan-2-yl)benzaldehyde. Furthermore, this study considers the change in its electronic and spectroscopic properties of this particular ester, when its boron atom is coordinated with a fluoride anion. The calculations were carried out using the LSDA and B3LYP functionals in Gaussian-16, and PBE in CASTEP. The results show that the B3LYP functional gives the best approximation to the experimental data. The formation of a coordinated covalent B-F bond highlights the remarkable sensitivity of the NMR chemical shifts of carbon, oxygen, and boron atoms and their surroundings. Furthermore, this bond also highlights the changes in the electron transitions bands n → π* and π → π* during the absorption and emission of a photon in the UV-vis, and in the stretching bands of the C=C bonds, and bending of BO2 in the infrared spectrum. This study not only contributes to the understanding of the properties of boronate esters but also provides important information on the interactions and responses optoelectronic of the compound when is bonded to a fluorine atom.

Growth and electronic properties of Co-doped Mn3O4 thin films: a combined experimental and theoretical investigation.

In this study, we have prepared and investigated the electronic properties of a new and promising cobalt doped Mn3O4 oxide surface by site-selective and element-sensitive X-ray-absorption (XAS) and photoemission spectroscopy (XPS and resonant PES) combined with density functional theory (DFT) calculations. The crystallinity of both pristine and Co doped thin films was ensured by low energy electron diffraction measurements, in which similar diffraction patterns were obtained for both films suggesting the inclusion of the dopant species within the crystalline Mn3O4 thin film. According to our combined experimental data and theoretical calculation results, XAS measurements and replace energy calculations could identify Co impurities adopting preferentially a 2+ oxidation state substituting a Mn2+ cation on tetrahedral sites (80%) as well as the Mn3+ on octahedral sites (20%). Direct evidence of these findings could be found by comparing the pristine Mn3O4 electron absorption and photoemission spectral features with those of the doped ones. For instance, the formation of oxygen vacancies related to the formation of Co2+ in an octahedral site could be directly observed. Remarkably, the valence band spectrum of Co-Mn3O4 thin films presents additional spectral features close to the Fermi edge that can be directly attributed to Co states when compared to the PDOS obtained by the DFT calculations. It is noteworthy that the formation and stabilization of these Co dopant species in the host Mn3O4 surface could potentially affect and obviously modulate its capability for adsorption of molecular species and transfer of electrons, which makes the cobalt doped Mn3O4 surface potentially promising for catalytic applications.

Information storage in permalloy modulated magnetic nanowires.

A long piece of magnetic material shaped as a central cylindrical wire (diameter [Formula: see text] nm) with two wider coaxial cylindrical portions (diameter [Formula: see text] nm and thickness [Formula: see text] nm) defines a bimodulated nanowire. Micromagnetism is invoked to study the equilibrium energy of the system under the variations of the positions of the modulations along the wire. The system can be thought of as composed of five independent elements (3 segments and 2 modulations) leading to [Formula: see text] possible different magnetic configurations, which will be later simplified to 4. We investigate the stability of the configurations depending on the positions of the modulations. The relative chirality of the modulations has negligible contributions to the energy and they have no effect on the stability of the stored configuration. However, the modulations are extremely important in pinning the domain walls that lead to consider each segment as independent from the rest. A phase diagram reporting the stability of the inscribed magnetic configurations is produced. The stability of the system was then tested under the action of external magnetic fields and it was found that more than 50 mT are necessary to alter the inscribed information. The main purpose of this paper is to find whether a prototype like this can be complemented to be used as a magnetic key or to store information in the form of firmware. Present results indicate that both possibilities are feasible.

Development of the open-source dose calculation and optimization toolkit matRad.

PURPOSE: We report on the development of the open-source cross-platform radiation treatment planning toolkit matRad and its comparison against validated treatment planning systems. The toolkit enables three-dimensional intensity-modulated radiation therapy treatment planning for photons, scanned protons and scanned carbon ions. METHODS: matRad is entirely written in Matlab and is freely available online. It re-implements well-established algorithms employing a modular and sequential software design to model the entire treatment planning workflow. It comprises core functionalities to import DICOM data, to calculate and optimize dose as well as a graphical user interface for visualization. matRad dose calculation algorithms (for carbon ions this also includes the computation of the relative biological effect) are compared against dose calculation results originating from clinically approved treatment planning systems. RESULTS: We observe three-dimensional γ-analysis pass rates ≥ 99.67% for all three radiation modalities utilizing a distance to agreement of 2 mm and a dose difference criterion of 2%. The computational efficiency of matRad is evaluated in a treatment planning study considering three different treatment scenarios for every radiation modality. For photons, we measure total run times of 145 s-1260 s for dose calculation and fluence optimization combined considering 4-72 beam orientations and 2608-13597 beamlets. For charged particles, we measure total run times of 63 s-993 s for dose calculation and fluence optimization combined considering 9963-45574 pencil beams. Using a CT and dose grid resolution of 0.3 cm3 requires a memory consumption of 1.59 GB-9.07 GB and 0.29 GB-17.94 GB for photons and charged particles, respectively. CONCLUSION: The dosimetric accuracy, computational performance and open-source character of matRad encourages a future application of matRad for both educational and research purposes.

Apuntes para la historia de las comunas de Recoleta e Independencia: períodos 1540-1915 / Notes on the history of the districts of Recoleta and Independence: 1540-1915 periods

Desde antes que sus callejones fueran tales, desde antes que sus calles fueran calles, hechos interesantes ya tenían lugar en la Chimba. A medida que la civilización y el progreso aumentaban en el país, aumentaba su gente y nuevas historias nacían cada mañana, en cada persona que a caballo, a pie, en carruaje o en carreta la cruzaba, fuere en son de paz o en son de guerra. En cada persona que la transformaba en su hogar, en cada persona que en ella levantaba un templo, una escuela, un claustro, un puente, una biblioteca, un hospital, un camposanto, una industria, un sindicato, una logia, un almacén, un estadio, un parque. En cada persona que también ahí vivió miserias y fracasos. En esta obra un puñado de historias cortas, aparentemente independientes las unas de las otras, pretende ir revelando el perfil de un barrio, su relación con el país; barrio que no por ser de los más antiguos es menos joven. En ellas, hasta en el más insignificante de los hechos, se descubren cosas de interés. En algunas se muestra su contemporaneidad con acontecimientos ocurridos en otros lugares del planta o en Chile mismo: mientras allá sucedía aquello, aquí pasaba esto otro. Desde un rincón de la Chimba también se puede atisbar el mundo. A lo mejor, con estas sencillas notas sobre la Chimba, con la rica iconografía que las apoya y con su bello diseño, en algo cooperaremos a enriquecer a los vercinos del sector, ahora Recoleta e Independencia, para quienes, principalmenter se hicieron estos apuntes. (AU)