Search Results (26)

This work describes the synthesis, crystal structure, and hydrophobicity tests of four bismuth(III)– and silver(I)–bromide complexes using the triammonium cations diethylenetriaminonium (H₃DETA³⁺) and N,N,N′,N″,N‴-pentamethyldiethylenetriammonium (H₃PMDTA³⁺). The prepared compounds are the 0D perovskites (H₃DETA)[BiBr₆] (1), (H₃DETA)₂[AgBr₄]Br₃ (2), and (H₃PMDTA)[BiBr₆] (3), as well as the 1D/2D mixed perovskite with minimum formula (H₃PMDTA)[Ag₃Br₆] (4), being the last three novel materials. Compounds 1 and 3 crystallize in the orthorhombic P2₁2₁2₁ space group and are discrete [BiBr₆]³⁻ units with the cation surrounding them. In both compounds, the bismuth(III) metal ion is found in a distorted octahedral coordination geometry. Compound 2 crystallizes in the monoclinic P2₁/c space group, and it is a mixed salt consisting of (H₃DETA)[AgBr₄] and (H₃DETA)Br₃, whereas the silver(I) complexes are also isolated. Finally, compound 4, which crystallizes in the orthorhombic space group Pbcn, is a combination of a 2D and 1D silver–bromide perovskite, with the cations filling the voids. The 2D structure has the minimal formula [Ag₄Br₇]³⁻, with the 1D coordination polymer [Ag₂Br₅]³⁻ being both built up by a combination of bromide ions acting as tetrahedra corner and edge-sharing bridging ligands. The silver(I) in 2 and 4 is found in a tetrahedral coordination geometry. All compounds were deposited on pristine FTO glass, resulting in an increase in the contact angle from 22° to 44°, 36°, 62°, and 54° for films of 1, 2, 3, and 4, respectively. Compounds 1 and 3 were also deposited onto Cs₂AgBiBr₆ film, and the contact angles were observed to be the same as when deposited directly onto the FTO cover glass. Full article

Layered orthorhombic single crystals of EuYCuTe₃ are synthesized using the ampoule method from the elemental precursors taken in the ratio of 1 Eu:1 Y:1 Cu:3 Te by heating up to 1120 K with an excess of CsI as flux. The orthorhombic structure of EuYCuTe₃ is established, and structural parameters are obtained using X-ray diffraction. At ambient conditions, the sample crystallizes in the space group Pnma with the unit cell parameters a = 11.2730(7) Å, b = 4.3214(3) Å, c = 14.3271(9) Å. The structure is composed of vertex-connected [CuTe₄]⁷⁻ tetrahedra, which form chains along the [010] direction, and of edge-connected [YTe₆]⁹⁻ octahedra, which form layers parallel to the (010) plane. The Eu²⁺ cations are found in a capped trigonal prismatic coordination of Te²⁻ anions. The structural phase transition from the α to the β phase is discovered upon heating the sample to 323 K, which comes accompanied with a decrease of [CuTe₄]⁷⁻ tetrahedral distortion. The symmetry of the high-temperature phase is established as ordered in the space group Cmcm (a = 4.3231(3) Å, b = 14.3328(9) Å, c = 11.2843(7) Å). The nature and microscopic mechanism of the phase transition is discussed. By cooling it down below 3 K, the soft ferromagnetic properties of EuYCuTe₃ are discovered. The correlation of the ferromagnetic transition temperature in the series of chalcogenides EuYCuCh₃ (Ch = S, Se, Te) with the ionic radius of the chalcogenide anion is established. The structural dynamical elastic properties of α- and β-EuYCuTe₃ were calculated within the ab initio approach. The vibrational mode frequencies and decomposition on irreducible representations, as well as the degree of ion involvement in each mode, were determined. The calculations reveal an imaginary mode in the Y-point of the Brillouin zone in the high symmetry β-EuYCuTe₃ phase. This finding explains the nature of structural reconstruction in EuYCuTe₃ crystal as a second-order phase transition induced by soft mode condensation at the edge of the Brillouin zone. The exfoliation of a single layer is simulated theoretically. The exfoliation energy is estimated, and the dynamical properties of EuYCuTe₃ single layers are studied. Full article

The packing and assembly of Platonic solids have fascinated mathematicians for ages. Recently, this fundamental geometrical problem has also attracted the attention of physicists, chemists, and engineers. This growing interest is due to the rapid advancements in various related fields, ranging from the formation of colloidal crystals and the design of metal–organic frameworks to the development of ultra-lightweight metamaterials, which are closely tied to the fast-evolving 3D printing technology. Numerous reports have focused on the assembly of Platonic polyhedra, particularly tetrahedra, for which an optimal packing strategy remains unidentified to this day. However, less attention has been given to the dodecahedron and its networks. This work introduces a new type of framework, designed from regular dodecahedra combined with icosahedron-based binders. The relatively simple design protocol employed here results in a remarkable variety of intriguing networks, which could be potentially useful in fields such as architecture, regenerative medicine, or aeronautics. Additionally, the dodecahedral networks presented in this study led to the discovery of intriguing structures resembling distorted graphene sheets. These structures exhibit features characteristic of both graphene and diamond. Full article

The layered orthorhombic quaternary tellurides EuRECuTe₃ (RE = Ho, Tm, Sc) with Cmcm symmetry were first synthesized. Single crystals of the compounds up to 500 μm in size were obtained by the halide-flux method at 1120 K from elements taken in a ratio of Eu/RE/Cu/Te = 1:1:1:3. In the series of compounds, the changes in lattice parameters were in the ranges a = 4.3129(3)–4.2341(3) Å, b = 14.3150(9)–14.1562(9) Å, c = 11.2312(7)–10.8698(7) Å, V = 693.40(8)–651.52(7) ų. In the structures, the cations Eu²⁺, RE³⁺ (RE = Ho, Tm, Sc), and Cu⁺ occupied independent crystallographic positions. The structures were built with distorted copper tetrahedra forming infinite chains [CuTe₄]⁷⁻ and octahedra [RETe₆]⁹⁻ forming two-dimensional layers along the a-axis. These coordination polyhedra formed parallel two-dimensional layers ${}_{\infty }{}^2\left\{{\left[\mathrm{C}\mathrm{u}RE{\mathrm{T}\mathrm{e}}_3\right]}^{2-}\right\}$. Between the layers, along the a-axis, chains of europium trigonal prisms [EuTe₆]¹⁰⁻ were located. Regularities in the variation of structural parameters and the degree of distortion of coordination polyhedra depending on the ionic radius of the rare-earth metal in the compounds EuRECuCh₃ (RE = Ho, Er, Tm, Lu, Sc; Ch = S, Se, Te) were established. It is shown that with a decrease in the ionic radius r_i(RE³⁺) in the compounds EuRECuTe₃, the unit-cell volume, bond length d(RE–Te), distortion degree [CuTe₄]⁷⁻, and crystallographic compression of layers [RECuTe₃]²⁻ decreased. The distortion degree of tetrahedral polyhedra [CuCh₄]⁷⁻, as well as the structural parameters in europium rare-earth copper tellurides EuRECuTe₃, were higher than in isostructural quaternary chalcogenides. Ab initio calculations of the crystalline structure, phonon spectrum, and elastic properties of compounds EuRECuTe₃ (RE = Ho, Tm, and Sc) ere conducted. The types and wave numbers of fundamental modes were determined, and the involvement of ions in IR and Raman modes was assessed. The calculated data of the crystal structure correlated well with the experimental results. Full article

This paper reports for the first time on a new layered magnetic heterometallic erbium telluride EuErCuTe₃. Single crystals of the compound were obtained from the elements at 1120 K using CsI as a flux. The crystal structure of EuErCuTe₃ was solved in the space group Cmcm (a = 4.3086(3) Å, b = 14.3093(9) Å, and c = 11.1957(7) Å) with the KZrCuS₃ structure type. In the orthorhombic structure of erbium telluride, distorted octahedra ([ErTe₆]⁹⁻) form two-dimensional layers (${}_{\infty }{}^2\left\{{\left[\mathrm{E}\mathrm{r}{\left(\mathrm{T}\mathrm{e}1\right)}_{2/2}^e{\left(\mathrm{T}\mathrm{e}2\right)}_{4/2}^k\right]}^{-}\right\})$, while distorted tetrahedra ([CuTe₄]⁷⁻) form one-dimensionally connected substructures (${}_{\infty }{}^1\left\{{\left[\mathrm{C}\mathrm{u}{\left(\mathrm{T}\mathrm{e}1\right)}_{2/2}^e{\left(\mathrm{T}\mathrm{e}2\right)}_{2/1}^t\right]}^{5-}\right\}$) along the [100] direction. The distorted octahedra and tetrahedra form parallel two-dimensional layers (${}_{\infty }{}^2\left\{{\left[\mathrm{C}\mathrm{u}\mathrm{E}\mathrm{r}{\mathrm{T}\mathrm{e}}_3\right]}^{2-}\right\})$ between which Eu²⁺ ions are located in a trigonal-prismatic coordination environment (${\left[{\mathrm{E}\mathrm{u}\mathrm{T}\mathrm{e}}_6\right]}^{10-})$. The trigonal prisms are connected by faces, forming chains (${}_{\infty }{}^1\left\{{\left[{\mathrm{E}\mathrm{u}\left(\mathrm{T}\mathrm{e}1\right)}_{2/2}{\left(\mathrm{T}\mathrm{e}2\right)}_{4/2}\right]}^{2-}\right\}$) along the [100] direction. Regularities in the variations in structural parameters were established in the series of erbium chalcogenides (EuErCuCh₃ with Ch = S, Se, and Te) and tellurides (EuLnCuTe₃ with Ln = Gd, Er, and Lu). Ab-initio calculations of the crystal structure, phonon spectrum, and elastic properties of the compound EuErCuTe₃ were performed. The types and wavenumbers of fundamental modes were determined, and the involvement of ions in the IR and Raman modes was assessed. The experimental Raman spectra were interpreted. The telluride EuErCuTe₃ at temperatures below 4.2 K was ferrimagnetic, as were the sulfide and selenide derivatives (EuErCuCh₃ with Ch = S and Se). Its experimental magnetic characteristics were close to the calculated ones. The decrease in the magnetic phase transition temperature in the series of the erbium chalcogenides was discovered. Full article

Hydrated H-Apophyllite (HH-Apo) and H-carletonite (H-Car) were synthesized at 0 °C by leaching an apophyllite and a carletonite single crystal in a large surplus of 1.2 molar hydrochloric acid. The XRD powder patterns of HH-Apo and H-Car were indexed with space group symmetries of P4/ncc and I4/mcm and lattice parameters of a = 8.4872(2) Å, c = 16.8684(8) Å and a = 13.8972(3) Å, c = 20.4677(21) Å, respectively. The crystal structures were solved based on model building of the structures of the precursors and a physico-chemical characterization. Rietveld structure refinements confirmed the structure models. HH-Apo and H-Car are among the very few crystalline silicic acids whose structures have been determined and confirmed based on a structure refinement. The structure of HH-Apo contains thin silicate monolayers that can be regarded as constructed by rings of interconnected [SiO₃OH] tetrahedra which form a puckered silicate layer. A sheet of water molecules is intercalated between the silicate layers. There are no direct hydrogen bonds between the silanol groups, but there are hydrogen bonds of different strengths between the terminal O atoms of the silicate layers and the intercalated water molecules. The ¹H MAS NMR spectrum presents a strong signal at 4.9 ppm related to the aforementioned bonds and interactions between the water molecules, as well as a small signal at 22.5 ppm corresponding to an extremely strong hydrogen bond with d(O...O) ≈ 2.2 Å. The structure of H-Car is free of structural water and consists exclusively of microporous silicate double-layers with 4-connected [SiO₄] and 3-connected [SiO₃OH] tetrahedra in a ratio of 1:1 and a thickness of 9.2 Å. Neighboring layers are connected to each other by medium–strong hydrogen bonds with O...O distances of 2.56 Å. The structure of HH-Apo decays within several hours while H-Car is stable. A topotactic condensation reaction applied to H-Car forms an irregularly condensed silicate which still contains the layers in a distorted form as building blocks. Full article

The superdense hexagonal boron pnictides BX (X = As, Sb, Bi), whose structures are formed by distorted tetrahedra and characterized by a quartz-derived (qtz) topology, have been predicted from first principles as potential high-pressure phases. From full geometry structure relaxation and ground state energy calculations based on quantum density functional theory (DFT), qtz BX was found to be mechanically (elastic constants) and dynamically (phonons) stable. From the energy–volume equations of state, at high but experimentally accessible pressures, qtz boron pnictides were found to be more energetically favorable than corresponding cubic zinc–blende phases with diamond-like (dia) topology. According to the electronic band structures, the zinc–blende BX have larger band gaps than the qtz phases, which can be attributed to the higher covalence of the latter. A metallic behavior is only observed for qtz BBi, which is related to the dynamic instability as it follows from the phonon band structure. Full article

The superdense hexagonal phosphides BP and AlP, whose structures are formed by distorted tetrahedra and characterized by quartz-derived (qtz) topology, were predicted from crystal chemistry and first principles as potential high-pressure phases. From full geometry structure relaxations and ground state energy calculations based on quantum density functional theory (DFT), qtz BP and AlP were found to be less cohesive than the corresponding cubic zinc-blende (zb) phases with diamond-like (dia) topology, but were confirmed to be mechanically (elastic constants) and dynamically (phonons) stable. From the energy–volume equations of state, qtz phases were found to be energetically favorable at small volumes (high pressures), with zb-to-qtz transition pressures of 144 GPa for BP and 28 GPa for AlP. According to the electronic band structures and the site projected density of states, both phosphides exhibit larger band gaps of the zinc-blende phases compared to the qtz phases; the smaller values for the latter result from the smaller volumes per formula unit, leading to increased covalence. Full article

Based on superdense C₆ with a quartz (qtz) topology, new ultrahigh-density hexagonal binary phases, qtz BN and qtz SiC, were identified via full geometry structure relaxations and ground state energies using calculations based on the quantum density functional theory (DFT) with a gradient GGA exchange–correlation XC functional. Like qtz C₆, with respect to diamond, the resulting binary qtz BN and qtz SiC were found to be less cohesive than cubic BN and cubic SiC, respectively, but were confirmed to be mechanically (elastic constants) and dynamically (phonon band structures) stable. Higher densities of the new phases correlate with higher hardness values compared to cubic BN and cubic SiC. In contrast to the regular tetrahedra that characterize the cubic BN and SiC phases, the corner-sharing tetrahedra in the new phases are distorted, which accounts for their exceptional density and hardness. All three qtz phases were found to be semiconducting to insulators, with reduced band gaps compared to diamond, cubic BN, and cubic SiC. Full article

Several ternary rare-earth metals containing titanium aluminum intermetallics in the RE₂TiAl₃ series (RE = Y, Gd–Lu) have been synthesized from the elements using arc-melting techniques. All compounds crystallize in the trigonal crystal system with rhombohedral space group R3m (Z = 3) and lattice parameters ranging between a = 582–570 and c = 1353–1358 pm. They adopt the Mg₂Ni₃Si-type structure, which is an ordered superstructure of the cubic Laves phase MgCu₂ and has been observed for Al intermetallics for the first time. Tetrahedral [TiAl₃] entities that are connected over all corners form a network where the empty [TiAl₃] tetrahedra exhibit a full Ti/Al ordering based on the single crystal results. The Al atoms are arranged into 6³ Kagomé nets, while the Ti atoms connect these nets over the triangular units. In the cavities of this three-dimensional arrangement, the RE cations can be found forming a distorted diamond-type substructure. Magnetic measurements revealed that Y₂TiAl₃ and Lu₂TiAl₃ are Pauli paramagnetic substances, in line with the metallic character. The other compounds exhibit paramagnetism with antiferromagnetic ordering at a maximum Néel temperature of T_N = 26.1(1) K for Gd₂TiAl₃. Full article

This paper reports for the first time on the new laminar quaternary orthorhombic heterometallic quaternary tellurides SrLnCuTe₃, the fabrication of which has been a challenge until this work. Data on the crystal structure of tellurides complete the series of quaternary strontium chalcogenides SrLnCuCh₃ (Ch = S, Se, Te). Single crystals of the compounds were synthesized from the elements by the halogenide-flux method at 1070 K. The compounds are crystallizing in two space groups Pnma (Ln = Sm, Gd and Tb) and Cmcm (Ln = Dy–Tm and Lu). For SrSmCuTe₃ (a = 11.4592(7), b = 4.3706(3), c = 14.4425(9) Å, space group: Pnma) with the largest lanthanoid cation, Sr²⁺ shows C.N. = 7, whereas Sm³⁺ reveals a diminished coordination number C.N. = 6. For SrLuCuTe₃ (a = 4.3064(3), b = 14.3879(9), c = 11.1408(7) Å, space group: Cmcm) with the smallest lanthanoid cation, coordination numbers of six are realized for both high-charged cations (Sr²⁺ and Lu³⁺: C.N. = 6). The cations Sr²⁺, Ln³⁺, Cu⁺ each take independent positions. The structures are built by distorted [CuTe₄]^7– tetrahedra, forming the infinite chains $\{_{\infty }^1{[\mathrm{Cu}{\left(\mathrm{Te}1\right)}_{1/1}^{\mathrm{t}}{\left(\mathrm{Te}2\right)}_{1/1}^{\mathrm{t}}{\left(\mathrm{Te}3\right)}_{2/2}^{\mathrm{e}}]}^{5-}\}$ along [010] in SrLnCuTe₃ (Ln = Sm, Gd and Tb) and [100] in SrLnCuTe₃ (Ln = Dy–Tm and Lu). The distortion of the polyhedra [CuTe₄]^7– was compared for the whole series SrLnCuTe₃ by means of τ₄-descriptor for the four coordinating Te^2– anions, which revealed a decrease in the degree of distortion with a decreasing radius at Ln³⁺. The distorted octahedra [LnTe₆]^9– form layers $\{_{\infty }^2{[Ln{\left(\mathrm{Te}1\right)}_{2/2}{\left(\mathrm{Te}2\right)}_{2/2}{\left(\mathrm{Te}3\right)}_{2/2}]}^{3-}\}$. The distorted octahedra and tetrahedra fuse to form parallel layers $\{_{\infty }^2{[\mathrm{Cu}Ln{\mathrm{Te}}_3]}^{2-}\}$ and between them, the Sr²⁺ cations providing three-dimensionality of the structure are located. In the SrLnCuTe₃ (Ln = Sm, Gd and Tb) structures, the Sr²⁺ cations center capped the trigonal prisms [SrTe₆₊₁]¹²⁻, united in infinite chains $\{_{\infty }^1{[\mathrm{Sr}{\left(\mathrm{Te}1\right)}_{2/2}{\left(\mathrm{Te}2\right)}_{3/3}{\left(\mathrm{Te}3\right)}_{2/2}]}^{4-}\}$ along the [100] direction. The domains of existence of the Ba₂MnS₃, BaLaCuS₃, Eu₂CuS₃ and KZrCuS₃ structure types are defined in the series of orthorhombic chalcogenides SrLnCuCh₃ (Ch = S, Se and Te). The tellurides SrLnCuTe₃ (Ln = Tb–Er) of both structure types in the temperature range from 2 up to 300 K are paramagnetic, without showing clear signs of a magnetic phase transition. Full article

The pentacadmium bis(vanadate(V)) tetrahydroxide Cd₅(VO₄)₂(OH)₄ was synthesized under hydrothermal conditions, and its crystal structure was determined with single-crystal X-ray diffraction. The investigated compound is the second known compound next to Cd(VO₃)₂·4H₂O synthesized in the CdO–V₂O₅–H₂O system and crystallizes isotypically to the minerals gatehouseite, Mn₅(PO₄)₂(OH)₄, and its As analog arsenoclasite, Mn₅(AsO₄)₂(OH)₄. Its symmetry is orthorhombic, with a space group of P2₁2₁2₁ and unit cell parameters of a = 19.011(4), b = 6.0133(12), c = 9.5411(19) Å, V = 1090.7(4) ų, and Z = 4. The structure consists of double ribbons of M(O,OH)₆-octahedra (M = Cd2, Cd3, Cd4) extending along [010] interconnected by edge- and corner-shared M(O,OH)₆-octahedra (M = Cd1, Cd5) and discrete, slightly distorted VO₄ tetrahedra, which form double chains of coupled polyhedra [V1O₄–Cd5O₄(OH)₂–Cd1O₅(OH)–V2O₄]_n running along the same direction. The interesting feature is the existence of V–Cd distances (3.0934(7) and 3.1081(7) Å for V1–Cd5 and V2–Cd1, respectively), which are shorter than the sum of the van der Waals radii of 3.71 Å. The V1–V2 distances of 4.1214(9) Å are also shorter than the sum of the van der Waals radii of 4.26 Å. The O–H···O hydrogen bonds additionally link the two subunits, ribbons, and chains into a three-dimensional structure. Raman spectra confirmed the presence of the hydrogen bonds and mutually isolated VO₄ groups. Full article

Two thiophosphates, KInP₂S₇ and KCrP₂S₇, were structurally characterized without investigating any optical properties. Herein in this work, KInP₂S₇ and KCrP₂S₇ were revisited to investigate their optical and magnetic properties, respectively. Pure polycrystalline samples and crystals of KInP₂S₇ and KCrP₂S₇ were grown by high temperature solid state reactions, where mm-sized crystals of KCrP₂S₇ were collected. KCrP₂S₇ is isostructural to KInP₂S₇, which features a layered structure. KInP₂S₇ and KCrP₂S₇ possess close relationship to the layered thiophosphate M₂P₂S₆ (M = Fe, Co, Zn, etc.). The bonding pictures of KInP₂S₇ were studied using the electron localization function (ELF) coupled with crystal orbital Hamilton population (COHP) calculations. The intrinsically distorted [PS₄] tetrahedra and [InS₆] octahedra are made by strong covalent P-S interactions and ionic In-S interactions, respectively. Electronic structure analysis confirmed that the optical properties of KInP₂S₇ are mainly contributed to by [PS₄] tetrahedra together with small amounts of the contributions coming from [InS₆] octahedra. Magnetic measurement on mm-sized crystals of KCrP₂S₇ verified that there is an antiferromagnetic transition around 21 K, and the Cr atoms are trivalent. KInP₂S₇ is predicated to be an indirect bandgap semiconductor of 2.38 eV, which is confirmed by the UV-Vis measurement of 2.4(1) eV. KInP₂S₇ is not a type-I phase-matching material and exhibits moderate second harmonic generation (SHG) response (0.51 × AgGaS₂, sample of particle size of 100 µm). The laser damage threshold (LDT) of KInP₂S₇ is very high of 5.2 × AgGaS₂. Bandgap engineering were undergone to enhance the SHG response of KInP₂S₇. Full article

Bismuth vanadate (BiVO₄) has attracted substantial attention on account of its usefulness in producing hydrogen by photoelectrochemical (PEC) water splitting. The exploitation of BiVO₄ for this purpose is yet limited by severe charge recombination in the bulk of BiVO₄, which is caused by the short diffusion length of the photoexcited charge carriers and inefficient charge separation. Enormous effort has been made to improve the photocurrent density and solar-to-hydrogen conversion efficiency of BiVO₄. This study demonstrates that modulating the composition of the electrode and the electronic configuration of BiVO₄ by decoration with silver nanoparticles (Ag NPs) is effective in not only enhancing the charge carrier concentration but also suppressing charge recombination in the solar water splitting process. Decoration with a small number of Ag NPs significantly enhances the photocurrent density of BiVO₄ to an extent that increases with the concentration of the Ag NPs. At 0.5% Ag NPs, the photocurrent density approaches 4.1 mA cm⁻² at 1.23 V versus a reversible hydrogen electrode (RHE) under solar simulated light illumination; this value is much higher than the 2.3 mA cm⁻² of pure BiVO₄ under the same conditions. X-ray absorption spectroscopy (XAS) is utilized to investigate the electronic structure of pure BiVO₄ and its modification by decoration with Ag NPs. Analytical results indicate that increased distortion of the VO₄ tetrahedra alters the V 3d–O 2p hybridized states. Additionally, as the Ag concentration increases, the oxygen vacancy defects that act as recombination centers in BiVO₄ are reduced. In situ XAS, which is conducted under dark and solar illumination conditions, reveals that the significantly enhanced PEC performance is attributable to the synergy of modulated atomic/electronic structures and the localized surface plasmon resonance effect of the Ag nanoparticles. Full article

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 [InAs₂As_2/2] 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⁺)(As^3–)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. Full article