Darstellung und kristallstruktur der calciumpnictidoxide Ca4P2O und Ca4As2O

Structural diversity among multinary pnictide oxides: a minireview focused on semiconducting and superconducting heteroanionic materials

Incorporating different anions with varied ionic sizes and charges is a rapidly growing approach to bring out unusual physical properties among various classes of solid-state materials, pnictides and chalcogenides in particular. This minireview is focused on hetero-anionic materials based on the pnictogens, which have been demonstrated to offer an impressive diversity of crystal chemistry and electronic structures. In addition, many pnictide oxides or oxypnictides, over the course of the last decade, have been shown to exhibit a broad spectrum of superconducting, magnetic, and semiconducting properties. However, the structural diversity of the mixed-anion materials is far greater than the several known structure types, or their variants, of the well-known layered superconductive materials. Therefore, with this treatise, we aim to provide a comprehensive overview of the crystal chemistry of pnictide oxides by recounting almost 40 different structures of such ternary and multinary compounds. In addition to the structural aspects, we also highlight some of the challenges associated with the synthesis, and briefly summarize reported, to date, physical properties of this remarkable class of solids.

Robust and synthesizable photocatalysts for CO2 reduction: a data-driven materials discovery

The photocatalytic conversion of the greenhouse gas CO₂ to chemical fuels such as hydrocarbons and alcohols continues to be a promising technology for renewable generation of energy. Major advancements have been made in improving the efficiencies and product selectiveness of currently known CO₂ reduction electrocatalysts, nonetheless, materials discovery is needed to enable economically viable, industrial-scale CO₂ reduction. We report here the largest CO₂ photocathode search to date, starting with 68860 candidate materials, using a rational first-principles computation-based screening strategy to evaluate synthesizability, corrosion resistance, visible-light absorption, and compatibility of the electronic structure with fuel synthesis. The results confirm the observation of the literature that few materials meet the stringent CO₂ photocathode requirements, with only 52 materials meeting all requirements. The results are well validated with respect to the literature, with 9 of these materials having been studied for CO₂ reduction, and the remaining 43 materials are discoveries from our pipeline that merit further investigation.

While the conversion of greenhouse CO₂ to chemical fuels offers a promising renewable energy technology, there is a dire need for new materials. Here, authors report the largest CO₂ photocathode search using a first-principles approach to identify both known and unreported candidate photocatalysts.

(La3 Z x)Al and (Ce3 Z x)Al with Z = C, N, O: preparation, physical properties and chemical bonding of metal-rich perovskites

The inverse cubic perovskites (La3O)Al, (La3N)Al, (Ce3O)Al, and (Ce3N)Al are reported together with the solid solution series (Ce3C1–xNx)Al. The crystal structure of (La3N)Al is analyzed in detail based on single crystal X-ray diffraction data (space group Pm-3m, a = 509.04(1) pm, Z = 1, R gt(F) = 0.008, wR(F 2) = 0.018). Combined X-ray powder diffraction and thermal analysis studies on samples with various N and O contents indicate only small tolerance of the ternary compounds towards Z = N, O deficiency and small solubility of Z in hexa gonal α-Ce3Al. Indications for the existence of a cubic β-Ce3Al with Cu3Au structure type could not be derived from any experiment. All studied phases are metals, the Ce compounds contain the rare-earth metal in Ce(4f 1) states according to X-ray absorption spectroscopy and measurements of the magnetic susceptibilities. The Ce moments order antiferromagnetically with T N decreasing and scaling with increasing unit cell dimension of the compounds. Electronic band structure calculations reveal a trend to increased mixing of Z and La states on going from Z = O via N to C. Formation of a band gap even in the formally electronically balanced (La3C)Al is mainly prohibited by insufficient charge transfer between the metal species.

Chemistry of layered d-metal pnictide oxides and their potential as candidates for new superconductors

Layered d-metal pnictide oxides are a unique class of compounds which consist of characteristic d-metal pnictide layers and metal oxide layers. More than 100 of these layered compounds, including the recently discovered Fe-based superconducting pnictide oxides, can be classified into nine structure types. These structure types and the chemical and physical properties of the characteristic d-metal pnictide layers and metal oxide layers of the layered d-metal pnictide oxides are reviewed and discussed. Furthermore, possible approaches to design new superconductors based on these layered d-metal pnictide oxides are proposed.