Synthesis, Structure, and Bonding of BaTl₃: An Unusual Competition between Cluster and Classical Bonding in the Thallium Layers

The new BaTl3 compound has been synthesized and characterized by physical property measurements and electronic structure calculations. Its structure (Cmcm) is a new intermediate in the Ni3Sn family (P63/mmc), and consists of thallium layers formed from two-center bond formation between the parallel chains of face-sharing octahedral clusters. The valence electron concentration (VEC) of the thallium layers is consistent with their two-dimensional nature, in comparison with those in other AX3-type compounds with one- or three-dimensional anionic networks with the same building blocks and different VECs. The unique geometric features of the anionic thallium layers bring on an unusual competition between inter- and intracluster bonds. Detailed studies of the energetics of BaTl3 reveal for the first time the important role of cation−anion interactions in the bonding competition in such an anionic substructure

Mn₁₄Al₅₆₊<i>_x</i>Ge_3-<i>_x</i> (<i>x</i> = 0−0.6): A New Intermetallic Phase Containing Unprecedented “Half-Broken” Mackay Icosahedra as Building Units

The new Mn14Al56+xGe3-x (x = 0−0.6) compounds of a new structure type have been synthesized and characterized by physical property measurements and electronic structure calculations. In contrast to their well-known silicon analogues, their unique structure (P3̄) exhibits unprecedented partially destroyed Mackay icosahedra that retain the icosahedral symmetry only in half of the individual polyhedra. The electronic band-structure analysis indicates that the chemical bonding in the structure is still optimized despite the destruction of the Mackay icosahedra and that a further valence electron concentration (VEC) optimization is achieved by the partial occupation of aluminum on a germanium site. The electronic band-structure calculation results were in agreement with the poor metallicity observed for the samples. While the Mn14Al56Ge3 is metallic, the resistivity of Mn14Al56.6Ge2.4 shows a minimum around 20 K and a maximum around 100 K. Both of the samples are Pauli-paramagnetic with an additional small Curie component

Orbital Interpretation of Kinetic Energy Density and a Direct Space Comparison of Chemical Bonding in Tetrahedral Network Solids

We present how the kinetic energy density (KED) can be interpreted on the basis of the orbital interactions within the Kohn−Sham theory and propose how to utilize a direct space function in chemical bonding analysis, the relative entropy density (RED), which is constructed from the KED, the Thomas−Fermi KED (TF-KED), and the electron density. From the detailed analysis of the KED of wave functions and the TF-KED from the free electron model, it is shown that the RED can reveal the nodal properties of individual wave functions and provide a variationally meaningful way of accumulating chemical bonding information from the wave functions, hence allowing quantitative bonding analysis in direct space. To substantiate the proposal, the RED function has been tested on the tetrahedral network solids, including the group 14 elements and the III−V binary compounds with the zinc blende structure. The direct space maps of the RED quantitatively reflect the trend in metallicity and the polarity of their two-center, two-electron bonds in terms of the absolute values of the RED, the location of the minimum values, and the behavior of the deformation from the spherical symmetry of the atomic RED

Mn₁₄Al₅₆₊<i>_x</i>Ge_3-<i>_x</i> (<i>x</i> = 0−0.6): A New Intermetallic Phase Containing Unprecedented “Half-Broken” Mackay Icosahedra as Building Units

The new Mn14Al56+xGe3-x (x = 0−0.6) compounds of a new structure type have been synthesized and characterized by physical property measurements and electronic structure calculations. In contrast to their well-known silicon analogues, their unique structure (P3̄) exhibits unprecedented partially destroyed Mackay icosahedra that retain the icosahedral symmetry only in half of the individual polyhedra. The electronic band-structure analysis indicates that the chemical bonding in the structure is still optimized despite the destruction of the Mackay icosahedra and that a further valence electron concentration (VEC) optimization is achieved by the partial occupation of aluminum on a germanium site. The electronic band-structure calculation results were in agreement with the poor metallicity observed for the samples. While the Mn14Al56Ge3 is metallic, the resistivity of Mn14Al56.6Ge2.4 shows a minimum around 20 K and a maximum around 100 K. Both of the samples are Pauli-paramagnetic with an additional small Curie component

Concomitant Thionation and Reduction of Graphene Oxide Through Solid/Gas Metathetical Sulfidation Reactions at High Temperatures

<div><p></p><p>We show that thionation of graphene oxide sheets is possible concomitantly with reduction of graphene oxide through a high-temperature (up to 500°C) solid/gas metathetical reaction process by employing gaseous boron sulfides as a thionation reagent which can effectively prevent the graphene oxide sheets from restacking during the heating. The X-ray photoelectron (XPS) and energy dispersive X-ray (EDS) spectroscopic studies revealed that reaction products have the S:O atomic ratios of about 2:1. The deconvolution of the high-resolution S2p XPS spectra of the product showed that about 90% of the sulfur atoms in the products are present in the form of C-SH. Ellman assay results indicated that practically all the thiols act as a free thiol which can participate in disulfide bond formation. From the thermogravimetric analysis (TGA) studies up to 600°C, the thiol functional groups in the products was found to be more thermally stable than hydroxyl groups. The estimated Tauc optical gap of the products is about 0.03 eV, which corroborates the reduced nature of the products.</p></div

Mn₁₄Al₅₆₊<i>_x</i>Ge_3-<i>_x</i> (<i>x</i> = 0−0.6): A New Intermetallic Phase Containing Unprecedented “Half-Broken” Mackay Icosahedra as Building Units

The new Mn14Al56+xGe3-x (x = 0−0.6) compounds of a new structure type have been synthesized and characterized by physical property measurements and electronic structure calculations. In contrast to their well-known silicon analogues, their unique structure (P3̄) exhibits unprecedented partially destroyed Mackay icosahedra that retain the icosahedral symmetry only in half of the individual polyhedra. The electronic band-structure analysis indicates that the chemical bonding in the structure is still optimized despite the destruction of the Mackay icosahedra and that a further valence electron concentration (VEC) optimization is achieved by the partial occupation of aluminum on a germanium site. The electronic band-structure calculation results were in agreement with the poor metallicity observed for the samples. While the Mn14Al56Ge3 is metallic, the resistivity of Mn14Al56.6Ge2.4 shows a minimum around 20 K and a maximum around 100 K. Both of the samples are Pauli-paramagnetic with an additional small Curie component

Synthesis, Structure, and Bonding of Hypoelectronic SrIn₄: Direct Example of a Dominant Size Effect in Structure Selection

The structure of the new title compound, the same type as EuIn4, was refined in the monoclinic space group C2/m, with Z = 4. The compound exhibits a complex three-dimensional network built of four- and five-bonded indium atoms in fused and interbonded pentagons that sandwich the strontium atoms. Both electronic band-structure calculations and property measurements show that the compound is metallic. A detailed band-structure analysis indicates that the compound is hypoelectronic with a one-electron deficiency, but the In−In bonding is effectively optimized in the structure. The important role of cation size in the structure choice is noted in a comparative study of BaIn4, which has the closely related BaAl4-type structure in which barium atoms are sandwiched by six-membered rings

Mn₁₄Al₅₆₊<i>_x</i>Ge_3-<i>_x</i> (<i>x</i> = 0−0.6): A New Intermetallic Phase Containing Unprecedented “Half-Broken” Mackay Icosahedra as Building Units

The new Mn14Al56+xGe3-x (x = 0−0.6) compounds of a new structure type have been synthesized and characterized by physical property measurements and electronic structure calculations. In contrast to their well-known silicon analogues, their unique structure (P3̄) exhibits unprecedented partially destroyed Mackay icosahedra that retain the icosahedral symmetry only in half of the individual polyhedra. The electronic band-structure analysis indicates that the chemical bonding in the structure is still optimized despite the destruction of the Mackay icosahedra and that a further valence electron concentration (VEC) optimization is achieved by the partial occupation of aluminum on a germanium site. The electronic band-structure calculation results were in agreement with the poor metallicity observed for the samples. While the Mn14Al56Ge3 is metallic, the resistivity of Mn14Al56.6Ge2.4 shows a minimum around 20 K and a maximum around 100 K. Both of the samples are Pauli-paramagnetic with an additional small Curie component

Synthesis, Structure, and Bonding of Open-Shell Sr₃In₅: An Unusual Electron Deficiency in an Indium Network, beyond the Zintl Boundary

The new title compound has been synthesized and characterized by physical property measurements and electronic structure calculations. The results ratify the highly uncommon deficiency of one electron that has been long speculated for its Ca3Ga5-type structure on the basis of the simple Zintl electron counting formalism. In the Sr3In5 structure (Cmcm), 4- and 2-bonded indium atoms in a 4:1 ratio form a three-dimensional classical network that encapsulates strontium atoms in its narrow channels. The electrical conductivity of the compound shows typical metallic behavior. The detailed electronic structure analysis suggests that the electron hole is mainly localized on a nonbonding p-orbital on the 2-bonded indium atoms, and that these orbitals, stacked in a σ-type way along a⃗ (4.97 Å), interact only weakly with each other to form highly one-dimensional bands

New Solid−Gas Metathetical Synthesis of Binary Metal Polysulfides and Sulfides at Intermediate Temperatures: Utilization of Boron Sulfides

A new simple synthetic method for binary metal polysulfides and sulfides was developed by utilizing an in situ formation of boron sulfides and their subsequent reactions with metal-source oxides in a closed container at intermediate temperatures above 350 °C at which the boron sulfides react in a gaseous form. The versatility of the new method is demonstrated with oxides of various transition metals (Ti, V, Mn, Fe, Ni, Nb, Mo, Ru, and W) and rare-earth metals (Y, Ce, Nd, Sm, Eu, Tb, and Er) as starting materials that exhibit different chemical characteristics. Regardless of the oxidation states of metals in the starting materials, the sulfidation reactions occurred quantitatively with stoichiometric mixtures of boron and sulfur, and within 24 h the reactions yielded pure products of TiS2, TiS3, VS4, FeS2, NiS2, NbS3, MoS2, RuS2, WS2, Y2S3, and RS2 (R = Ce, Nd, Sm, Eu, Tb, and Er) which were the thermodynamically stable phases under the reaction conditions. The scope and implications of the new sulfidation method are also discussed