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The ternary Zintl phase, Yb2CdSb2, was discovered to exist in two different polymorphic forms. In addition to the orthorhombic α-Yb2CdSb2 (space group Cmc21) known for its excellent thermoelectric properties, we present the synthesis and characterization of the crystal and electronic structure of its monoclinic variant, β-Yb2CdSb2. Structural characterization was performed with the single-crystal X-ray diffraction method. β-Yb2CdSb2 crystallizes in a monoclinic crystal system with the non-centrosymmetric space group Cm (Z = 33, a = 81.801(5) Å, b = 4.6186(3) Å, c = 12.6742(7) Å, β = 93.0610(10)°) and constitutes a new structure type. The complex crystal structure of β-Yb2CdSb2 contrasts with the previously studied β-Ca2CdPn2 (Pn = P, As, Sb) polymorphs, although it shares similar structural features. It consists of three different layers, made of corner-sharing [CdSb4] tetrahedra and stacked in the ABC sequence. The layers are interconnected via [CdSb3] trigonal planar units. Multiple Yb and Cd atomic sites exhibit partial occupancy, resulting in extensive structural disorder. Valence electron partitioning within the Zintl–Klemm formalism yields the formulation (Yb2+)1.98(Cd2+)1.01(Sb3−)2(h+)0.02, highlighting the nearly charge-balanced composition. Detailed electronic structure calculations reveal the closed band gap and presumably semimetallic nature of β-Yb2CdSb2 with the band structure features hinting at potential topological properties.

Reported herein are the synthesis and crystal chemistry analysis of the Zintl phase Sr21Cd4Sb18. Single crystals of this compound were grown using the Sn-flux method, and structural characterization was carried out using single-crystal X-ray diffraction. Crystal data: Monoclinic space group C2/m (No. 12, Z = 4); a = 18.2536(6) Å, b = 17.4018(5) Å, and c = 17.8979(6) Å, β = 92.024(1)°. The structure is based on edge- and corner-shared CdSb4 tetrahedra, which ultimately form octameric [Cd8Sb22] fragments, where two symmetry-equivalent subunits are connected via a homoatomic Sb–Sb interaction. The electronic band structure calculations contained herein reveal the emergence of a direct gap between the valence and the conduction bands.

Abstract Topological semimetals such as Dirac, Weyl or nodal line semimetals are widely studied for their peculiar properties including high Fermi velocities, small effective masses and high magnetoresistance. When the Dirac cone is tilted, exotic phenomena could emerge whereas materials hosting such states are promising for photonics and plasmonics applications. Here we present evidence that SrAgBi is a spin-orbit coupling-induced type-II three-dimensional Dirac semimetal featuring tilted Dirac cone at the Fermi energy. Near charge compensation and Fermi surface characteristics are not much perturbed by 7% of vacancy defects on the Ag atomic site, suggesting that SrAgBi could be a material of interest for observation of robust optical and spintronic topological quantum phenomena.

Three novel binary barium arsenides, Ba3As4, Ba5As4, and Ba16As11, were synthesized and their crystal and electronic structures were investigated. Structural data collected via the single-crystal X-ray diffraction method indicate that the anionic substructures of all three novel compounds are composed of structural motifs based on the homoatomic As–As contacts, with [As2]4− dimers found in Ba5As4 and Ba16As11, and an [As4]6− tetramer found in Ba3As4. Ba3As4 and Ba5As4 crystallize in the orthorhombic crystal system—with the non-centrosymmetric space group Fdd2 (a = 15.3680(20) Å, b = 18.7550(30) Å, c = 6.2816(10) Å) for the former, and the centrosymmetric space group Cmce (a = 16.8820(30) Å, b = 8.5391(16) Å, and c = 8.6127(16) Å) for the latter—adopting Eu3As4 and Eu5As4 structure types, respectively. The heavily disordered Ba16As11 structure was solved in the tetragonal crystal system with the space group P4¯21m (a = 12.8944(12) Å and c = 11.8141(17) Å). The Zintl concept can be applied to each of these materials as follows: Ba3As4 = (Ba2+)3[As4]6−, Ba5As4 = (Ba2+)5(As3−)2[As2]4−, and 2 × Ba16As11 = (Ba2+)32(As3−) ≈ 20[As2]4− ≈ 1, pointing to the charge-balanced nature of these compounds. Electronic structure calculations indicate narrow bandgap semiconducting behavior, with calculated bandgaps of 0.47 eV for Ba3As4, 0.34 eV for Ba5As4, and 0.33 eV for Ba16As11.

The calcium- and strontium- alumo-germanides SrxCa1–xAl2Ge2 (x ≈ 0.4) and SrAl2Ge2 have been synthesized and structurally characterized. Additionally, a binary calcium germanide CaGe has also been identified as a byproduct. All three crystal structures have been established from single-crystal X-ray diffraction methods and refined with high accuracy and precision. The binary CaGe crystallizes with a CrB-type structure in the orthorhombic space group Cmcm (no. 63; Z = 4; Pearson symbol oC8), where the germanium atoms are interconnected into infinite zigzag chains, formally [Ge]2−. The calcium atoms are arranged in monocapped trigonal prisms, centered by Ge atoms. SrxCa1−xAl2Ge2 (x ≈ 0.4) and SrAl2Ge2 have been confirmed to crystallize with a CaAl2Si2-type structure in the trigonal space group P3¯m1 (no. 164; Z = 1; Pearson symbol hP5), where the germanium and aluminum atoms form puckered double-layers, formally [Al2Ge2]2−. The calcium atoms are located between the layers and reside inside distorted octahedra of Ge atoms. All presented structures have a valence electron count satisfying the octet rules (e.g., Ca2+Ge2− and Ca2+[Al2Ge2]2−) and can be regarded as Zintl phases.

A novel binary compound within the Ba–Sb phase diagram, Ba5Sb8, was synthesized by combining elements with an excess of Sb in an alumina crucible. Structural elucidation was performed using single-crystal X-ray diffraction. This compound crystallizes in the orthorhombic space group Fdd2 with unit cell parameters of a = 15.6568(13) Å, b = 35.240(3) Å, c = 6.8189(6) Å, adopting its own structure type. The most distinctive features of the structure are the eight-membered [Sb8]10− polyanionic fragments which have no known precedents among antimonides. They are separated by five Ba2+ cations, which afford the charge balance and enable adherence to the Zintl–Klemm formalism. Ba5Sb8 is the highest known member of the homologous series within the family of barium antimonides BanSb2n−2 (n ≥ 2), all of which boast anionic substructures with oligomeric moieties of pnictogen atoms with varied lengths and topologies. Electronic structure calculations indicate an indirect narrow bandgap of ca. 0.45 eV, which corroborates the valence-precise chemical bonding in Ba5Sb8.

The compounds AELi2Ge (AE = Ca, Sr and Ba) were synthesized, and their structures were determined as a part of the exploratory work in the Li-rich regions of the respective ternary systems. The three compounds are isostructural, and their crystal structure is analogous with the orthorhombic structure of BaLi2Si and KLi2As (space group Pmmn). The atomic arrangement can be viewed as an intergrowth of corrugated AEGe layers, alternated with slabs of Li atoms, suggestive of the possible application of these phases as electrode materials for lithium-ion batteries. Both experimental electronic density and calculated electronic structure suggest the existence of Li–Li and Li–Ge interactions with largely covalent character. Despite that, the valence electrons can be partitioned as (AE2+)(Li+)2(Ge4–), i.e., the title compounds can be viewed as valence-precise Zintl phases. The band structure calculations for BaLi2Ge show that a bona fide energy gap in the band structure does not exist and that the expected poor metallic behavior is originated from the AEGe sub-lattice and related to hybridization of Ba5d and Ge3p states in the valence band in proximity of the Fermi level. In addition, electrochemical measurements indicate that Li atoms can be intercalated into CaGe with a maximum capacity of 446 mAh/g, close to the theoretical value of 480 mAh/g of CaLi2Ge, which reveals the possibility of this Li-rich compound to be used as an electrode in Li-ion batteries.

Reported are the synthesis and structural characterization of a series of quaternary lithium-alkaline earth metal alumo-silicides and alumo-germanides with the base formula A2LiAlTt2 (A = Ca, Sr, Ba; Tt = Si, Ge). To synthesize each compound, a mixture of the elements with the desired stoichiometric ratio was loaded into a niobium tube, arc welded shut, enclosed in a silica tube under vacuum, and heated in a tube furnace. Each sample was analyzed by powder and single-crystal X-ray diffraction, and the crystal structure of each compound was confirmed and refined from single-crystal X-ray diffraction data. The structures, despite the identical chemical formulae, are different, largely dependent on the nature of the alkaline earth metal. The differing cation determines the structure type—the calcium compounds are part of the TiNiSi family with the Pnma space group, the strontium compounds are isostructural with Na2LiAlP2 with the Cmce space group, and the barium compounds crystallize with the PbFCl structure type in the P4/nmm space group. The anion (silicon or germanium) only impacts the size of the unit cell, with the silicides having smaller unit cell volumes than the germanides.

A new ternary phase has been synthesized and structurally characterized. BaLixCd13–x (x ≈ 2) adopts the cubic NaZn13 structure type (space group Fm3¯c, Pearson symbol cF112) with unit cell parameter a = 13.5548 (10) Å. Structure refinements from single-crystal X-ray diffraction data demonstrate that the Li atoms are exclusively found at the centers of the Cd12-icosahedra. Since a cubic BaCd13 phase does not exist, and the tetragonal BaCd11 is the most Cd-rich phase in the Ba–Cd system, BaLixCd13–x (x ≈ 2) has to be considered as a true ternary compound. As opposed to the typical electron count of ca. 27e-per formula unit for many known compounds with the NaZn13 structure type, BaLixCd13–x (x ≈ 2) only has ca. 26e-, suggesting that both electronic and geometric factors are at play. Finally, the bonding characteristics of the cubic BaLixCd13–x (x ≈ 2) and tetragonal BaCd11 are investigated using the TB-LMTO-ASA method, showing metallic-like behavior.

This work details the synthesis and the crystal structures of the quaternary Zintl phases Na2CaCdSb2, Na2SrCdSb2 and Na2EuCdSb2. They are isostructural and their noncentrosymmetric structure is with the space group Pmc21 (Pearson code oP12). All structural work is carried out via single-crystal X-ray diffraction methods. The structure features [CdSb2]4– layers of corner-shared CdSb4 tetrahedra, which are stacked along the b-crystallographic axis and are separated by cations. The results from the structure refinements suggest that in addition to full cation ordering, which is typical for this structure, there also exists a possibility for an accommodation of a small degree of cation disorder.

Crystals of a new ternary compound in the Ca-In-As family, Ca3InAs3, have been successfully synthesized via flux growth techniques. This is only the third known compound between the respective elements. As elucidated by single-crystal X-ray diffraction measurements, Ca3InAs3 crystallizes in the orthorhombic space group Pnma (No. 62, Pearson symbol oP28) with unit cell parameters a = 12.296(2) Å, b = 4.2553(7) Å, and c = 13.735(2) Å. The smallest building motifs of the structure are InAs4 tetrahedra, which are connected to one another by shared As corners, forming infinite [InAs2As2/2] chains. The latter propagate along the crystallographic b-axis. The As-In-As bond angles within the InAs4 tetrahedra deviate from the ideal 109.5° value and range from 98.12(2)° to 116.53(2)°, attesting to a small distortion from the regular tetrahedral geometry. Electronic structure calculations indicate the opening of a bandgap, consistent with the expected (Ca2+)3(In3+)(As3–)3 formula breakdown based on conventional oxidation numbers. The calculations also show that the Ca–As interactions are an intermediate between covalent and ionic, while providing evidence of strong covalent features of the In–As interactions. Weak s-p hybridization of In states was observed, supporting the experimentally found deviation of the InAs4 moiety from the ideal tetrahedral symmetry.

Electronic band structures of the following compounds – Cs4Cd(As7)2, K2PdP2, K5CuAs2, Na2CuP and K3Cu3P2 – all computed by means of the TB-LMTO-ASA code. The calculations show that for all compounds, the bonding states are occupied, while the antibonding orbitals are vacant. This confirms the partitioning of the valence electrons according to the Zintl–Klemm formalism. The data is related to doi.org/10.1016/j.jssc.2018.11.029 (Ovchinnikov and Bobev, 2019) [1].

The guest‐free, type‐II Si clathrate (Si136) is an open cage polymorph of Si with structural features amenable to electrochemical Li storage. However, the detailed mechanism for reversible Li insertion and migration within the vacant cages of Si136 is not established. Herein, X‐ray characterization and density functional theory (DFT) calculations are used to understand the structural origin of electrochemical Li insertion into the type‐II clathrate structure. At low Li content, instead of alloying with Si, topotactic Li insertion into the empty cages occurs at ≈0.3 V versus Li/Li+ with a capacity of ≈231 mAh g−1 (corresponding to composition Li32Si136). A synchrotron powder X‐ray diffraction analysis of electrodes after lithiation shows evidence of Li occupation within the Si20 and Si28 cages and a volume expansion of 0.22%, which is corroborated by DFT calculations. Nudged elastic band calculations suggest a low barrier (0.2 eV) for Li migration through interconnected Si28 cages, whereas there is a higher barrier for Li migration into Si20 cages (2.0 eV). However, if Li is present in a neighboring cage, a cooperative migration pathway with a barrier of 0.65 eV is possible. The results show that the type‐II Si clathrate displays unique electrochemical properties for potential applications as Li‐ion battery anodes.

The Zintl phase Ca14AlBi11 has been synthesized and structurally characterized for the first time. Its crystal structure has been carefully determined by single-crystal X-ray diffraction methods, and shown to crystallize in the tetragonal space group I41/acd, No. 142 (Z = 8). Not surprisingly, Ca14AlBi11 adopts the Ca14AlSb11-structure type, although Ca14AlBi11 is the first alumo-bismuthide among the ‘14–1–11’ family whose structure is unequivocally established. In the respective Ca–Al–Bi ternary system, so far, Ca14AlBi11 is only the second identified phase. Electronic structure calculations for this new bismuthide indicate the opening of a small gap at the Fermi level, suggestive of intrinsic semiconducting behavior. Resistivity measurements on as-synthesized single crystalline sample show temperature dependence akin to those of heavily doped semiconductors or the bad metals. In addition to the moderately high electrical conductivity (ρ300 = 1.05 mΩ cm), specimens of Ca14AlBi11 also exhibit excellent thermopower, with high-temperature (HT) values of the Seebeck coefficient approaching and possibly exceeding 200 μV/K. These metrics, coupled with preliminary HT conductivity estimates, are comparable with the best state-of-the-art p-type Zintl thermoelectric materials and are among the best within the known bismuthides with the same atomic arrangements. Therefore, Ca14AlBi11 represents a new platform for the development of a novel, low-cost thermoelectric materials family with first-class transport properties and enhanced thermal stability. Initial data suggest that Ca14AlBi11 is amenable to doping, which opens up many opportunities for tuning charge-carrier concentration and optimizing the transport properties in this new, HT thermoelectric material.

The flux growth method was successfully employed to synthesize millimeter-sized single crystals of the ternary barium vanadium pnictides Ba5V12As19+x (x ≈ 0.02) and Ba5V12Sb19+x (x ≈ 0.36), using molten Pb and Sb, respectively. Both compositions crystallize in space group P4̄3m and adopt a structure similar to those of the barium titanium pnictides Ba5Ti12Pn19+x (Pn = Sb, Bi), yet with a subtly different disorder, involving the pnictogen and barium atoms. Attempts to obtain an arsenide analog of Ba5Ti12Pn19+x using a Pb flux technique yielded binary arsenides. High-temperature treatment of the elements Ba, Ti, and As in Nb or Ta tubes resulted in side reactions with the crucible materials and produced two isostructural compositions Ba8Ti13−xMxAs21 (M = Nb, Ta; x ≈ 4), representing a new structure type. The latter structure displays fcc-type metal clusters comprised of statistically distributed Ti and M atoms (M = Nb, Ta) with multi-center and two-center bonding within the clusters, as suggested by our first-principle calculations.

We report discovery of antiferromagnetic semimetal EuZnSb_{2}, obtained and studied in the form of single crystals. Electric resistivity, magnetic susceptibility, and heat capacity indicate antiferromagnetic order of Eu with T_{N} = 20 K. The effective moment of Eu^{2+} inferred from the magnetization and specific heat measurement is 3.5 μ_{B}, smaller than the theoretical value of Eu^{2+} due to presence of both Eu^{3+} and Eu^{2+}. Magnetic-field-dependent resistivity measurements suggest dominant quasi-two-dimensional Fermi surfaces whereas the first-principle calculations point to the presence of Dirac fermions. Therefore, EuZnSb_{2} could represent the first platform to study the interplay of dynamical charge fluctuations, localized magnetic 4f moments, and Dirac states with Sb orbital character.

The new quaternary phases Eu5Zn2As5O and Eu5Cd2As5O have been synthesized by metal flux reactions and their structures have been established through single-crystal X-ray diffraction. Both compounds crystallize in the centrosymmetric space group Cmcm (No. 63, Z = 4; Pearson symbol oC52), with unit cell parameters a = 4.3457(11) Å, b = 20.897(5) Å, c = 13.571(3) Å; and a = 4.4597(9) Å, b = 21.112(4) Å, c = 13.848(3) Å, for Eu5Zn2As5O and Eu5Cd2As5O, respectively. The crystal structures include one-dimensional double-strands of corner-shared MAs4 tetrahedra (M = Zn, Cd) and As–As bonds that connect the tetrahedra to form pentagonal channels. Four of the five Eu atoms fill the space between the pentagonal channels and one Eu atom is contained within the channels. An isolated oxide anion O2– is located in a tetrahedral hole formed by four Eu cations. Applying the valence rules and the Zintl concept to rationalize the chemical bonding in Eu5M2As5O (M = Zn, Cd) reveals that the valence electrons can be counted as follows: 5 × [Eu2+] + 2 × [M2+] + 3 × [As3–] + 2 × [As2–] + O2–, which suggests an electron-deficient configuration. The presumed h+ hole is confirmed by electronic band structure calculations, where a fully optimized bonding will be attained if an additional valence electron is added to move the Fermi level up to a narrow band gap (Eu5Zn2As5O) or pseudo-gap (Eu5Cd2As5O). In order to achieve such a formal charge balance, and hence, narrow-gap semiconducting behavior in Eu5M2As5O (M = Zn, Cd), europium is theorized to be in a mixed-valent Eu2+/ Eu3+ state.

Exploratory studies in the systems Rb–Ga–Sn and Cs–Ga–Sn yielded the cubic type-I clathrates with refined compositions Rb8GaxSn46−x and Cs8GaxSn46−x (6.9 < x < 7.5). Nearly single-phase materials with good crystallinity were obtained from stoichiometric reactions of the elements. The structures were characterized by means of single-crystal X-ray diffraction methods. Both Rb8GaxSn46−x and Cs8GaxSn46−x represents cases, where a Group 13 element randomly substitutes a Group 14 element in the structure. The extent of Ga/Sn mixing is apparently governed by the drive of the system to achieve an optimal valence electron count, and hence, Rb8GaxSn46−x and Cs8GaxSn46−x (x ≈ 8) can be regarded as Zintl phases. This notion is supported by structure refinements on a multitude of single-crystal X-ray diffraction data, which also confirm that both types of cages in the cubic type-I structure are fully occupied by Rb and Cs atoms. The open-framework, comprised of 46 nodes per formula unit, adapts to the incorporation of nearly eight Ga atoms within the matrix of Sn, whereby small, short-range distortions result. The exact nature of these effects is still unclear, as so far, the structural variations could only be modeled as both positional and occupational disorder at one of three framework sites. Since vacancies in the structures of the binary type-I clathrates A8Sn46−x☐x (A = Rb, Cs; ☐ = missing Sn atom) are also known to cause local distortions, the latter were also synthesized with the same protocols used for the synthesis of A8GaxSn46−x and structurally re-analyzed. The results from the latter studies confirm that homogeneity issues abound, and that the final structures/compositions are an intricate function of the experimental conditions.

Magnetic frustration in metals is scarce and hard to pinpoint, but exciting due to the possibility of the emergence of fascinating novel phases. The cubic intermetallic compound HoInCu_{4} with all holmium atoms on an fcc lattice exhibits partial magnetic frustration, yielding a ground state where half of the Ho moments remain without long-range order, as evidenced by our neutron scattering experiments. The substitution of In with Cd results in HoCdCu_{4} in a full breakdown of magnetic frustration. Consequently we found a fully ordered magnetic structure in our neutron diffraction experiments. These findings are in agreement with the local energy scales and crystal electric field excitations, which we determined from specific heat and inelastic neutron scattering data. The electronic density of states for the itinerant bands acts as a tuning parameter for the ratio between nearest-neighbor and next-nearest-neighbor interactions and thus for magnetic frustration.

The new ternary arsenides AE3TrAs3 (AE = Sr, Ba; Tr = Al, Ga) and their phosphide analogs Sr3GaP3 and Ba3AlP3 have been prepared by reactions of the respective elements at high temperatures. Single-crystal X-ray diffraction studies reveal that Sr3AlAs3 and Ba3AlAs3 adopt the Ba3AlSb3-type structure (Pearson symbol oC56, space group Cmce, Z = 8). This structure is also realized for Sr3GaP3 and Ba3AlP3. The compounds Sr3GaAs3 and Ba3GaAs3 crystallize with the Ba3GaSb3-type structure (Pearson symbol oP56, space group Pnma, Z = 8). Both structures are made up of isolated pairs of edge-shared AlPn4 and GaPn4 tetrahedra (Pn = pnictogen, i.e., P or As), separated by the alkaline-earth Sr2+ and Ba2+ cations. In both cases, there are no homoatomic bonds, hence, regardless of the slightly different atomic arrangements, both structures can be rationalized as valence-precise [AE2+]3[Tr3+][Pn3−]3, or rather [AE2+]6[Tr2Pn6]12−, i.e., as Zintl phases.

Systematic studies in the systems Cs–Na–Ga–Si, Rb–Na–Ga–Si, and Rb–Na–Zn–Si yielded the novel type-I clathrates with refined compositions Cs6Na2Ga8.25Si37.75(3), Rb6.34Na1.66(2)Ga8.02Si37.98(3), and Rb5.20Na2.80(4)Zn3.85Si42.15(2) (cubic, ), as well as the type-II clathrates with formulae Cs8Na16Ga22.7Si113.3(1), Rb8.4Na15.6(1)Ga19.6Si116.4(1), and Rb8Na16Zn8.4Si127.6(1) (cubic, ). In each system, the type-I and -II compounds are always co-crystallizing, irrespective of the reaction conditions. The structures derived from single-crystal X-ray diffraction confirm complete ordering of Cs and Na atoms, and nearly complete ordering of the Rb and Na guest atoms. The framework-building Si atoms are randomly substituted by Ga or Zn atoms on all framework sites with notable difference in the substitution patterns between the type-I and type-II structure. This, and other details of the crystal chemistry are discussed in this paper.

The new Zintl compounds RbNa8Ga3Pn6 (Pn = P, As) and Na10NbGaAs6 have been synthesized from the corresponding elements at high temperatures. RbNa8Ga3P6 and RbNa8Ga3As6 crystallize with a novel structure type that features trigonal planar [Ga3P6]9– and [Ga3As6]9– motifs, which are isosteric with the 1,3,5-trioxanetrione (a cyclic trimer of carbon dioxide). Na10NbGaAs6, an unforeseen side product of the same reactions boasts a structure, which is based on NbAs4 and GaAs4 tetrahedra, condensed by sharing common edges into [NbGaAs6]10– dimers. The bonding characteristics of both structures are discussed. All three compounds reported herein represent the first compounds found in the respective quaternary systems.

Synthesis and single-crystal X-ray structure determination of the new antimonide oxide, Ba5Cd2Sb4O2 are reported. Ba5Cd2Sb4O2 crystallizes in the monoclinic space group C2/m (No. 12) with unit cell parameters: a = 17.247(7) Å, b = 4.9279(18) Å, c = 12.240(5) Å, and β = 132.558(4)°; Z = 2. Its crystal structure can be described as a polyanionic [Cd2Sb4]6– sub-lattice made up of fused CdSb4 tetrahedra, stacked between puckered slabs of oxo-anions, O2–, and Ba2+ cations. This structure can also be described as a “double-salt”, i.e., a structure composed of fragments from the Zintl phase Ba3Cd2Sb4 intercalated by two BaO-like moieties. The topological similarities between the structures of these compounds are discussed.

Systematic syntheses in the Ba–Ga–Sn system confirmed the existence of a new ternary phase BaGa1.79Sn4.21(2) (EuGa2Ge4 structure type; orthorhombic space group Cmcm, Pearson symbol oS28) with lattice parameters a = 4.5383(6) Å, b = 12.2486(16) Å, c = 14.3747(19) Å. The structure is best viewed as an open-framework based on tetrahedrally coordinated Sn/Ga atoms with Ba atoms enclosed in the voids within it. The new phase co-precipitates with two other compounds with very similar compositions—Ba8Ga14.5Sn31.5(4) (K4Si23 structure type; cubic space group , Pearson symbol cP54; a = 11.6800(12) Å), and Ba8Ga13.2Sn32.8(3), (Eu4Ga8Ge15 structure type; cubic space group , Pearson symbol cI54; a = 11.5843(7) Å). Detailed discussion on how syntheses affect the crystal chemistry, and the temperature dependence of the atomic displacement parameters, obtained from single-crystal structure refinements, are also reported in this article.

Investigations of the system Ba–In–Sn, with the objective to synthesize Ba8In16Sn30 clathrate using Sn and In flux reactions, yielded instead the known BaSn3 compound (P63/mmc; a = 7.228(2) Å, c = 5.469(3) Å) from Sn flux and its In-doped variant BaSn2.8In0.2(1) (a = 7.260(1) Å, c = 5.382(2) Å) from In flux. BaSn3–xInx is the first, and up until now, the only ternary phase containing these elements. Its structure is isomorphic with the Ni3Sn type (Pearson symbol hP8) and is apparently capable of sustaining small variations in the valence electron count by virtue of replacing Sn with the electron poorer In. Electrical resistivity measurements on single-crystals of both undoped and doped phases show different metallic-like behavior, suggesting that neither BaSn3 nor BaSn3–xInx are valence compounds.

Three new cluster compounds, Cs2NaAs7, Cs4ZnAs14, and Cs4CdAs14 were obtained from high temperature reactions. Their structures feature heptaarsenide [As7]3– anions, where the clusters in Cs4ZnAs14 and Cs4CdAs14 are dimerized by the linkers Zn and Cd, respectively. The bonding characteristics of these clusters are discussed and compared. Band structure calculation on Cs2NaAs7 suggests that this compound is a semiconductor with an energy gap of circa 1.6 eV, which is in consistent with the dark red color of the crystals.

Reported are the synthesis and crystal structure of Ba7Li11Bi10, a new ternary compound crystallizing in its own type with the monoclinic space group C2/m (a = 18.407(3) Å, b = 5.0258(9) Å, and c = 18.353(3) Å; β = 104.43(1)°; Pearson symbol mS56), and those of the structurally related quaternary phases Ba4(Li1−xGax)7Sb6, Ba4(Li1−xInx)7Sb6, Ba4(Li1−xInx)7Bi6, and Eu4(Li1−xInx)7Bi6 (crystallizing in the Eu4Li7Bi6 structure type with the same monoclinic space group C2/m (a = 18.4045(13)–17.642(4) Å, b = 5.012(4)–4.8297(10) Å, and c = 13.2792(10)–12.850(3) Å, β = 126.80(1)–125.85(1)°; Pearson symbol mS34). All studied compounds are identified among the products of the high-temperature reactions of the corresponding elements. Both types of crystal structures are based on corner- and edge-linked Li-centered Sb4 (or Bi4) tetrahedra, Sb6 (or Bi6) octahedra, and Sb2 or Bi2 dumbbells. Given the similarities between the two structures, it might be proposed that they represent the simplest members of a potentially large homologous series described with the general formulae (BaLi3Sb2)n(Ba3Li4Sb4)m or (BaLi3Bi2)n(Ba3Li4Bi4)m, where the more complicated “7-11-10” phase is the member with n = 2 and m = 1, while the “4-7-6” one is the intergrowth of the two components in an equal ratio. The computed electronic band structures of Ba7Li11Bi10 and idealized Ba4Li7Bi6 (a model for Ba4(Li1−xInx)7Bi6) are also discussed.

The title compound, Eu5Cd2Sb5O adopts the Ba5Cd2Sb5F-type structure (Pearson symbol oC52), which contains nine crystallographically unique sites in the asymmetric unit, all on special positions. One Eu, two Sb, and the Cd atom have site symmetry m..; two other Eu, the third Sb and the O atom have site symmetry m2m; the remaining Eu atom has 2/m.. symmetry. Eu atoms fill pentagonal channels built from corner-sharing CdSb4 tetrahedra. The isolated O atom, i.e., an oxide ion O2−, is located in a distorted tetrahedral cavity formed by four Eu cations.

Ba2Cd2.13Bi3O, a new bismuthide(-I,-III) oxide, crystallizes with a novel body-centered tetragonal structure (Pearson code tI36). The crystal structure contains eight crystallographically unique sites in the asymmetric unit, all on special positions. Two Ba, one Cd and two Bi atoms have site symmetry 4mm, the third Bi atom has mmm. and the O atom has overline{4}m2 symmetry; the second Cd site (2mm. symmetry) is not fully occupied. The layered structure is complex and can be considered as an intergrowth of two types of slabs, viz. BaCdBiO with the ZrCuSiAs type and BaCd2Bi2 with the CeMg2Si2 type.

The title compound, Yb2LiInGe2, a new ordered quaternary intermetallic phase, crystallizes with the orthorhombic Ca2LiInGe2 type (Pearson code oP24). The crystal structure contains six crystallographically unique sites in the asymmetric unit, all in special positions with site symmetry .m.. The structure is complex and based on [InGe4] tetrahedra, which share corners in two directions, forming layers parallel to (001). Yb atoms fill square-pyramidal (Yb1) and octahedral (Yb2) interstices between the [InGe4/2] layers, while the small Li+ atoms fill tetrahedral sites.

The title compound, Eu11Zn6As12, crystallizes with the Sr11Cd6Sb12 structure type (Pearson's symbol mC58). The complex monoclinic structure of the first arsenide to form with this type features chains made of corner-sharing ZnAs4 tetrahedra, separated by Eu atoms. There are a total of 15 unique positions in the asymmetric unit. Except for one Eu atom with site symmetry 2/m, all atoms are located on mirror planes. An usual aspect of the structure are some Zn—As distances, which are much longer than the sum of the covalent radii, indicating weaker interactions.