Novel noncentrosymmetric (K0.38Ba0.81)Ga2Se4 can be obtained from centrosymmetric BaGa2Se4via partial substitution, and it demonstrates promising balanced NLO properties.

Developing alternatives to Pt catalysts is a prerequisite to cost-effectively produce hydrogen. Herein, we demonstrate Ru P nanoparticles (without any doping and modifications) as a highly efficient Pt-like catalyst for the hydrogen evolution reaction (HER) in different pH electrolytes. On transferring the hexagonal close-packed crystal structure of Ru to the orthorhombic structure of Ru P, a greatly improved catalytic activity and stability toward HER is found owing to Ru-P coordination. The electronic state change originates from the P-Ru bonding structures, which accounts for the HER activity improvement compared with Ru nanoparticles. Specifically, Ru P nanoparticles can drive 10 mA cm at a very low overpotential of 55 mV, only 8 mV more than Pt/C in an acidic solution; and an extremely low overpotential of approximately 50 mV is needed in alkaline solution, about 20 mV less than the Pt/C catalyst. The Volmer-Tafel mechanism is indicated on Ru P nanoparticles with the typical Tafel slope of 30 mV dec of Pt metal indicating a Pt-like catalytic ability. Ru P is more active in the Ru-P family as H atoms prefer to adsorb on Ru atoms rather than on the P element according to theoretical calculations. Considering the low price of Ru (20 % of Pt), anti-corrosion ability in the electrolyte, and the safe and reliable fabrication approach, the powder Ru P nanoparticles make an excellent HER catalyst with great promise for large-scale water electrolysis applications.

This article focuses on the synthesis and the crystal chemistry of six members of a series of rare-earth metal based germanides with general formula RELiGe(2) (RE = La-Nd, Sm, and Eu). The structures of these compounds have been established by single-crystal X-ray diffraction (CaLiSi(2) structure type, space group Pnma, Z = 4, Pearson symbol oP16). The chemical bonding within this atomic arrangement can be rationalized in terms of anionic germanium zigzag chains, conjoined via chains of edge-shared LiGe(4) tetrahedra and separated by rare-earth metal cations. The structure can also be viewed as an intergrowth of AlB(2)-like and TiNiSi-like fragments, or as the result of the replacement of 50% of the rare-earth metal atoms by lithium in the parent structure of the REGe monogermanides. Except for LaLiGe(2) and SmLiGe(2), the remaining four RELiGe(2) phases exhibit Curie-Weiss paramagnetism above about 50 K. In the low temperature regime, the localized 4f electrons in CeLiGe(2), PrLiGe(2), and SmLiGe(2) order ferromagnetically, while antiferromagnetic ordering is observed for NdLiGe(2) and EuLiGe(2). The calculated effective magnetic moments confirm RE(3+) ground states in all cases excluding EuLiGe(2), in which the magnetic response is consistent with Eu(2+) configuration (J = S = 7/2). The experimental results have been complemented by tight-binding linear muffin-tin orbital (TB-LMTO) band structure calculations.

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This study focuses on the exploration of the ternary systems A-Li-Pn with A = Ca-Ba, Eu and Yb and Pn = As-Bi resulting in the extensions of the ALiPn series (A = Ca, Sr, Eu and Yb; Pn = As-Bi; orthorhombic Pnma) with the MgSrSi structure type and of the A3Li4Pn4 family (A = Ba, Eu; Pn = As-Bi; orthorhombic Immm) with the Zr3Cu4Si4 structure type, as well as the novel compound Eu4Li7Bi6 (monoclinic, C2/m) with its own structure type. The relevant structural relationships are discussed. The building blocks and the topology of the polyanionic networks among the three different structures are compared side-by-side. Electronic band structure calculations for EuLiSb, Eu3Li4Sb4 and Eu4Li7Bi6 are discussed; the magnetic susceptibility and resistivity of single-crystalline Eu3Li4Sb4 are also presented.