Two new non-centrosymmetric ternary compounds, MgSiAs 2 and Mg 3 Si 6 As 8 , are discovered via metal flux and solid-state synthetic methods. MgSiAs 2 belongs to the well-known II-IV-V 2 family, which is extensively studied experimentally and computationally for their optical properties. MgSiAs 2 is computationally predicted but not experimentally known prior to this work. Mg 3 Si 6 As 8 crystallizes in a new non-centrosymmetric cubic chiral structure type with the Pearson symbol cP68. The syntheses, crystal structure, thermal and chemical stabilities, electronic structures, and optical properties of these two new compounds are investigated in this work. Optical absorption measurements and electronic structure calculations reveal the two compounds to be direct or pseudo-direct bandgap semiconductors (1.8-2 eV). The crystal structures of both compounds are non-centrosymmetric, though Mg 3 Si 6 As 8 belongs to the 432 chiral crystal class, which is optically active but does not exhibit second harmonic generation (SHG) behavior. The SHG response of MgSiAs 2 is 60% of that for AgGaS 2 , but MgSiAs 2 exhibits a higher laser damage threshold than AgGaS 2 at 33.2 MW cm −2 .

Lithiation of van der Waals tetrel‐arsenides, GeAs and SiAs, has been investigated. Electrochemical lithiation demonstrated large initial capacities of over 950 mAh g−1 accompanied by rapid fading over successive cycling in the voltage range 0.01–2 V. Limiting the voltage range to 0.5–2 V achieved more stable cycling, which was attributed to the intercalation process with lower capacities. Ex situ powder X‐ray diffraction confirmed complete amorphization of the samples after lithiation, as well as recrystallization of the binary tetrel‐arsenide phases after full delithiation in the voltage range 0.5–2 V. Solid‐state synthetic methods produce layered phases, in which Si‐As or Ge‐As layers are separated by Li cations. The first layered compounds in the corresponding ternary systems were discovered, Li0.9Ge2.9As3.1 and Li3Si7As8, which crystallize in the Pbam (No. 55) and P2/m (No. 10) space groups, respectively. Semiconducting layered GeAs and SiAs accommodate the extra charge from Li cations through structural rearrangement in the Si‐As or Ge‐As layers and eventually by replacement of the tetrel dumbbells with sets of Li atoms. Ge and Si monoarsenides demonstrated high structural flexibility and a mild ability for reversible lithiation.

No abstract

Cs y M x Si1–x As2 (M = Cu, Zn, or Ga; y = 0.15–0.19; x depends on M) represents a new group of pseudo-two-dimensional compounds that allow property tuning with various metal substituents without alteration of the main Si–As two-dimensional framework. Their crystal structure is built from M x Si1–x As2 layers separated by disordered chains of Cs cations. These compounds are synthesized using a CsCl flux as a source of Cs, circumventing the need for an expensive and air-sensitive Cs metal reagent. M-Si substitution is required to compensate for the excess electrons donated by Cs cations. Alternatively, the charge compensation can be achieved by the formation of As vacancies. Resistivity measurements confirm the electron-balanced nature of the compounds that exhibit semiconducting behavior with small bandgaps.

Over 20 years after the last inorganic ternary B-P compound was reported, Na2BP2, a new compound containing onedimensional B-P polyanionic chains has been synthesized. Common high-temperature synthetic methods required for the direct reaction of boron and phosphorus negate the possible formation of metastable or low temperature phases. In this study, oxidative elimination was used to successfully condense 0D BP2 3anionic monomers found in Na3BP2 precursor into unique 1D BP2 2chains consisting of 5-member B2P3 rings connected by bridging P atoms in the crystal structure of Na2BP2. The synthesis was guided by in-situ X-ray powder diffraction studies, which revealed the metastable nature of the products of oxidative elimination reactions. Na2BP2 is predicted to be an electron balanced semiconductor which was confirmed by UV-vis spectroscopy with the experimentally determined bandgap of 1.1 eV. UV-vis spectroscopy.

Magnesium, element no. 12 on the periodic table, is the second member of the alkaline-earth metal family. Often, Mg is considered as an electropositive metal like its heavier congeners, Ca, Sr, and Ba. In this review, another important aspect of Mg chemistry, namely, the ability to form covalent bonds to more electronegative elements, is considered with a focus on pnictides. Magnesium's flexible coordination numbers and bond distances are similar to those of main group elements (Al) or late-and post-transition metals (Mn, Cu, Zn, Cd). In this work, selected Mg-pnictides are discussed to emphasize the chemical and structural diversity of Mg which results in a variety of physical properties. Thermoelectric, Mg-ion battery, and nonlinear optical applications of select Mg-containing compounds are summarized, providing examples on the exploitation of Mg chemical bonding flexibility for the design of novel functional materials.

Loss of the inversion center in the crystal structure is represented by varied bond lengths and distorted bond angles as a tetrahedron passes through a looking glass. In article number https://doi.org/10.1002/adfm.201801589, Kirill Kovnir and co‐workers demonstrate a high tendency for Mg–Si–As compounds to crystallize in non‐centrosymmetric space groups.

An isostructural series of transition metalformate-chloride-hydrate compounds, M 3 (OOCH) 5 Cl(OH 2 ) (M = Fe, Co, Ni), have been synthesized using a solvothermal method. These compounds crystallize in the chiral and polar space group P3 1 and are comprised of three different types of helical chains of edge-sharing M 2+ -centered octahedra. All three compounds undergo 3D ferrimagnetic ordering at low temperature, and the iron and cobalt analogues exhibit fieldinduced metamagnetic transitions. The magnetic structure was determined by neutron powder diffraction, revealing ferromagnetic intrachain coupling and antiferromagnetic interchain interactions, with the three chains arranged in a two-up/onedown triangular lattice. As all three chains contain one type of metal in the same spin state, these compounds are rare examples of homospin topological ferrimagnets.