Two novel ternary compounds in a La−Zn−P system, La 2 Zn 11 P 9 and La 7 Zn 2 P 11 , were synthesized via hightemperature transport reactions. The crystal structures for both compounds were established by means of single crystal X-ray diffraction. The complex three-dimensional (3D) crystal structure of metal-rich La 3 Zn 2 P 4 is composed of a Zn−P framework with large channels accommodating four atomic columns of La atoms. The isolated columns of La atoms alternating with Zn−P tetrahedral chains and disordered P 3 chains, resembling polyacene fragments, build up the crystal structure of phosphorus-rich La 7 Zn 2 P 11. The previously reported La 3 Zn 2−x P 4 compound with intermediate phosphorus content has a two-dimensional (2D) structural motif composed of Zn 2 P 2 and La 3 P 2 layers. A structural dimensionality reduction from 3D La 2 Zn 11 P 9 to 2D La 3 Zn 2-x P 4 to 1D La 7 Zn 2 P 11 is due to both the flexibility of the Zn−P framework with ZnP 4 tetrahedra and ZnP 3 planar building units and the ability of phosphorus to form homonuclear bonds and polyatomic phosphorus chains. A polycrystalline sample La 3 Zn 1.75 P 4 was purified by a high-temperature solid-state method. The electron counting rules and computations predict the n-type metallic nature of La 3 Zn 1.75 P 4 . The transport properties tests performed on a sintered pellet of La 3 Zn 1.75 P 4 confirm its metallic behavior with negative thermopower indicating that the major carriers are electrons. La 3 Zn 1.75 P 4 exhibits moderate thermal conductivity, 4.5 W m −1 K −1 at 300 K, where lattice thermal conductivity has the dominating contributions.

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.

A new clathrate solid solution Ba8Cu16 − xAuxP30 (x = 4, 8, 12) was synthesized by a high-temperature solid-state annealing method. The crystal structures of Ba8Cu16 − xAuxP30 were determined by single crystal x-ray diffraction. This clathrate solid solution crystallizes in the orthorhombic superstructure of clathrate-I type with 23 crystallographically independent framework sites, eight of them are occupied by Au/Cu and 15 are exclusively occupied by P atoms. The distribution of Au and Cu atoms over these eight framework sites is not random with a clear preference for Au to occupy the largest (Au/Cu)P4 tetrahedra in the framework. The thermal stability and thermoelectric properties of the Ba8Cu16 − xAuxP30 solid solution were evaluated. Low thermal conductivity was achieved for Ba8Cu16 − xAuxP30 due to the combination of the host–guest crystal structure with rattling Ba atoms with the presence of heavy Au atoms and substitutional Cu/Au disorder in the clathrate framework.