Crystal, electronic structure and hydrogenation properties of the Mg5.57Ni16Ge7.43 cluster phase with a new type of polyhedron.

The ternary germanide Mg5.57Ni16Ge7.43 (cubic, space group Fm-3m, cF116) belongs to the structural family based on the Th6Mn23-type. The Ge1 and Ge2 atoms fully occupy the 4a (m-3m symmetry) and 24d (m.mm) sites, respectively. The Ni1 and Ni2 atoms both fully occupy two 32f sites (.3m symmetry). The Mg/Ge statistical mixture occupies the 24e site with 4m.m symmetry. The structure of the title compound contains a three-core-shell cluster. At (0,0,0), there is a Ge1 atom which is surrounded by eight Ni atoms at the vertices of a cube and consequently six Mg atoms at the vertices of an octahedron. These surrounded eight Ni and six Mg atoms form a [Ge1Ni8(Mg/Ge)6] rhombic dodecahedron with a coordination number of 14. The [GeNi8(Mg/Ge)6] rhombic dodecahedron is encapsulated within the [Ni24] rhombicuboctahedron, which is again encapsulated within an [Ni32(Mg/Ge)24] pentacontatetrahedron; thus, the three-core-shell cluster [GeNi8(Mg/Ge)6@Ni24@Ni32(Mg/Ge)24] results. The pentacontatetrahedron is a new representative of Pavlyuk's polyhedra group based on pentagonal, tetragonal and trigonal faces. The dominance of the metallic type of bonding between atoms in the Mg5.57Ni16Ge7.43 structure is confirmed by the results of the electronic structure calculations. The hydrogen sorption capacity of this intermetallic at 570 K reaches 0.70 wt% H2.

Synthesis, crystal structure and hydrogenation properties of MgxLi3 - xB48 - y (x = 1.11, y = 0.40).

The ternary magnesium/lithium boride, MgxLi3 - xB48 - y (x = 1.11, y = 0.40, idealized formula MgLi2B48), crystallizes as its own structure type in P43212, which is closely related to the structural family comprising α-AlB12, Be0.7Al1.1B22 and tetra-gonal ß-boron. The asymmetric unit of title structure contains two statistical mixtures Mg/Li in Wyckoff sites 8b with relative occupancies Mg:Li = 0.495 (9):0.505 (9) and 4a with Mg:Li = 0.097 (8):0.903 (8). The boron atoms occupy 23 8b sites and two 4a sites. One of the latter sites has a partial occupancy factor of 0.61 (2). Both unique Mg/Li atoms adopt a twelvefold coordination environment in the form of truncated tetra-hedra (Laves polyhedra). These polyhedra are connected by triangular faces to four [B12] icosa-hedra. The boron atoms exhibit four kinds of polyhedra, namely penta-gonal pyramid (coordination number CN = 6), distorted tetra-gonal pyramid (CN = 5), bicapped hexa-gon (CN = 8) and gyrobifastigium (CN = 8). At the gas hydrogenation of MgLi2B48 alloy, formation of the eutectic composite hydride LiBH4+Mg(BH4)2 and amorphous boron is observed. In the temperature range 543-623 K, the hydride eutectics decompose, forming MgH2, LiH, MgB4, B and H2.

A new ternary derivative of the Laves phases in the Mg-Co-Ga system.

Crystal structures of MgCoGa, Mg0.74CoGa0.52 and Mg0.49CoGa0.15 phases from the Mg-Co-Ga system were investigated using single-crystal diffraction. These structures belong to the family of so-called Laves phases. Hexagonal MgCoGa crystallizes as a disordered phase within the MgZn2 structure type. The orthorhombic structure of Mg0.74CoGa0.52 is a distortion variant of MgZn2 and URe2 structure type, and the structural relation is demonstrated in terms of a Bärnighausen formalism group-subgroup transformation scheme. The structure of trigonal phase Mg0.49CoGa0.15 is strongly disordered, as is shown by the presence of adjacent atomic sites which cannot be occupied simultaneously. In Mg0.49CoGa0.15, two subcells (A and B) were obtained in a ratio of 9:1. Subcell A is closely related to MgZn2-type.

Tb2-xNdxZn17-yNiy (x = 0.5, y = 4.83): a new intermetallic with a maximum disordered structure and its hydrogen storage properties.

The ternary Tb2-xNdxZn17-yNiy (x = 0.5, y = 4.83) disordered phase belongs to the structural family based on the rhombohedral Th2Zn17 structure type. The structure is maximally disordered since all the sites are occupied by statistical mixtures of atoms. The Tb/Nd mixture of atoms occupies the 6c site (site symmetry 3m). The statistical mixtures Ni/Zn consisting of more Ni atoms are located in the 6c and 9d (symmetry .2/m) sites. In the following 18f (site symmetry .2) and 18h (site symmetry .m) sites are located Zn/Ni statistical mixtures which consist of more Zn atoms. Zn/Ni atoms form three-dimensional networks with hexagonal channels that fill statistical mixtures of Tb/Nd and Ni/Zn. The Tb2-xNdxZn17-yNiy compound belongs to the family of intermetallic phases capable of absorbing hydrogen. In the structure, there are three types of voids, namely, 9e (site symmetry .2/m), 3b (site symmetry -3m) and 36i (site symmetry 1), in which hydrogen can be inserted, and the maximum total absorption capacity can reach 1.21 wt% H2. Electrochemical hydrogenation shows that the phase absorbs 1.03% of H2, which indicates partial filling of the voids with H atoms.

Synthesis and Structural Studies of New Selenium Derivatives Based on Covalent Functionalization of MWCNTs.

Modifying the surface of nanomaterials, such as carbon nanotubes, by introducing heteroatoms or larger functional groups into the structure causes a change in chemical properties-manifested in the increase in reactivity as well as a change in conductivity. This paper presents the new selenium derivatives obtained by a covalent functionalization of brominated multi-walled carbon nanotubes (MWCNTs). The synthesis was carried out in mild conditions (3 days at room temperature), and was additionally assisted with ultrasound. After a two-stage purification, the obtained products were identified and characterized by the following methods: scanning and transmission electron microscopy imaging (SEM and TEM), energy dispersive X-ray microanalysis (EDX), X-ray photoelectron spectroscopy (XPS), Raman and nuclear magnetic resonance (NMR), and X-ray diffraction (XRD). In the selenium derivatives of carbon nanotubes, the content of selenium and phosphorus reached 14 and 4.2 wt%, respectively.

MgMn4Ga18: a novel three-shell gallium cluster structure.

The new ternary gallide MgMn4Ga18 (magnesium tetramanganese octadecagallium) was synthesized and its crystal structure determined by means of single-crystal X-ray diffraction. The MgMn4Ga18 structure can be described as that of a three core-shell cluster compound. The Mg atoms are surrounded by 16 adjacent Ga atoms, [MgGa16], and the respective coordination polyhedron is an octadecahedron. This [MgGa16] octadecahedron is encapsulated inside a [Ga32] icohexahedron, which is in turn encapsulated inside a [Ga40] pentacontaoctahedron. As a result, a three core-shell cluster, [MgGa16@Ga32@Ga40], is identified. Electronic structure calculations were performed by means of the TB-LMTO-ASA program and additionally confirm the existence of the core-shell packing of the clusters.

Synthesis, crystal structure and Hirshfeld surface analysis of 5-cyclo-propyl-N-(2-hy-droxy-eth-yl)-1-(4-methyl-phen-yl)-1H-1,2,3-triazole-4-carboxamide.

The title compound, C15H18N4O2, was obtained via a two-step synthesis (Dimroth reaction and amidation) for anti-cancer activity screening and was selected from a 1H-1,2,3-triazole-4-carboxamide library. The cyclo-propyl ring is oriented almost perpendicular to the benzene ring [dihedral angle = 87.9 (1)°], while the dihedral angle between the mean plane of the cyclo-propyl ring and that of the triazole ring is 55.6 (1)°. In the crystal, the mol-ecules are linked by O-H⋯O and C-H⋯N inter-actions into infinite ribbons propagating in the [001] direction, which are inter-connected by weak C-H⋯O inter-actions into layers. The inter-molecular inter-actions were characterized via Hirshfeld surface analysis, which indicated that the largest fingerprint contact percentages are H⋯H (55.5%), N⋯H/H⋯N (15.4%), C⋯H/H⋯C (13.2%) and O⋯H/H⋯O (12.9%).

Effect of Continuous and Discontinuous Microwave-Assisted Heating on Starch-Derived Dietary Fiber Production.

Dietary fiber can be obtained by dextrinization, which occurs while heating starch in the presence of acids. During dextrinization, depolymerization, transglycosylation, and repolymerization occur, leading to structural changes responsible for increasing resistance to starch enzymatic digestion. The conventional dextrinization time can be decreased by using microwave-assisted heating. The main objective of this study was to obtain dietary fiber from acidified potato starch using continuous and discontinuous microwave-assisted heating and to investigate the structure and physicochemical properties of the resulting dextrins. Dextrins were characterized by water solubility, dextrose equivalent, and color parameters (L* a* b*). Total dietary fiber content was measured according to the AOAC 2009.01 method. Structural and morphological changes were determined by means of SEM, XRD, DSC, and GC-MS analyses. Microwave-assisted dextrinization of potato starch led to light yellow to brownish products with increased solubility in water and diminished crystallinity and gelatinization enthalpy. Dextrinization products contained glycosidic linkages and branched residues not present in native starch, indicative of its conversion into dietary fiber. Thus, microwave-assisted heating can induce structural changes in potato starch, originating products with a high level of dietary fiber content.

Enhancement of Y5-xPrxSb3-yMy (M = Sn, Pb) Electrodes for Lithium- and Sodium-Ion Batteries by Structure Disordering and CNTs Additives.

The maximally disordered (MD) phases with the general formula Y5-xPrxSb3-yMy (M = Sn, Pb) are formed with partial substitution of Y by Pr and Sb by Sn or Pb in the binary Y5Sb3 compound. During the electrochemical lithiation and sodiation, the formation of Y5-xPrxSb3-yMyLiz and Y5-xPrxSb3-yMyNaz maximally disordered-high entropy intermetallic phases (MD-HEIP), as the result of insertion of Li/Na into octahedral voids, were observed. Carbon nanotubes (CNT) are an effective additive to improve the cycle stability of the Y5-xPrxSb3-yMy (M = Sn, Pb) anodes for lithium-ion (LIBs) and sodium-ion batteries (SIBs). Modification of Y5-xPrxSb3-ySny alloys by carbon nanotubes allowed us to significantly increase the discharge capacity of both types of batteries, which reaches 280 mAh · g-1 (for LIBs) and 160 mAh · g-1 (for SIBs), respectively. For Y5-xPrxSb3-yPby alloys in which antimony is replaced by lead, these capacities are slightly smaller and are 270 mAh · g-1 (for LIBs) and 155 mAh · g-1 (for SIBs), respectively. Results show that structure disordering and CNT additives could increase the electrode capacities up to 30% for LIBs and up to 25% for SIBs.

A Facile and Efficient Bromination of Multi-Walled Carbon Nanotubes.

The bromination of multi-walled carbon nanotubes (MWCNT) was performed with vapor bromine in a closed vessel, and they were subjected to intensive stirring with a magnetic stirrer for up to 14 days. The efficiency of bromination was compared depending upon duration. The structure and surface of the crude and purified products were characterized by detailed physicochemical analyses, such as SEM/EDS, TEM, XRD, TGA, Raman, and XPS spectroscopies. The studies confirmed the presence of bromine covalently bound with nanotubes as well as the formation of inclusion MWCNT-Br2 complexes. It was confirmed that Br2 molecules are absorbed on the surface of nanotubes (forming the CNT-Br2 complex), while they can dissociate close to dangling bonds at CNT defect sites with the formation of covalent C-Br bonds. Thus, any covalent attachment of bromine to the graphitic surface achieved around room temperature is likely related to the defects in the MWCNTs. The best results, i.e., the highest amount of attached Br2, were obtained for brominated nanotubes brominated for 10 days, with the content of covalently bound bromine being 0.68 at% (by XPS).

Structural and enhanced hydrogen storage properties of the Li12Mg3Si3Al phase.

The multicomponent alumosilicide Li12Mg3Si3Al (cubic, space group I-43d, cI76) belongs to the structural family based on the Cu15Si4 type. The Li atoms are ordered and occupy the site with symmetry 1 and the Mg atoms occupy the site with -4.. symmetry. The Si/Al statistical mixture occupies the site with .3. symmetry. The coordination polyhedra around the Li atoms are 13-vertex distorted pseudo-Frank-Kasper polyhedra. The environments of the Mg and Si/Al atoms are icosahedral. The hydrogen storage characteristics of Li12Mg3Si3Al were investigated. The reversible hydrogen storage capacity of the title compound is excellent and the gravimetric storage capacity of this new material, corresponding to 9.1 wt% H2, is higher compared to Li12Mg3Si4 (8.8 wt%). The enthalpy of hydrogen desorption is 86 kJ mol-1 and is lower compared to known lithium-based hydrides.

New cubic cluster phases in the Mg-Ni-Ga system.

The crystal structure of new Mg9Ni6Ga14 and Mg3Ni2Ga compounds were investigated by single-crystal diffraction. Both structures can be described as three-core-shell cluster compounds. In the Mg6Ni9Ga14 structure, the [Ni6Ga6] icosahedron is encapsulated within the [Mg20] dodecahedron, which is again encapsulated within a [Ni18Ga42] fullerene-like truncated icosahedron, thus the three core-shell cluster [Ni6Ga6@Mg20@Ni18Ga42] results. In the Mg3Ni2Ga structure, the [Mg6] octahedron is encapsulated within the [Ni12Ga6] flattened icosahedron in vertices of which there are 12 nickel atoms, and six lateral edges are centered by gallium atoms, which in turn is encapsulated within a [Mg36] pseudo-rhombicuboctahedron with 12 additional atoms centering the lateral faces; thus for Mg3Ni2Ga the three-shell cluster is [Mg6@Ni12Ga6@Mg36].

A new monoclinic structure type for ternary gallide MgCoGa2.

The crystal structure of MgCoGa2 (magnesium cobalt digallide) was solved by direct methods and refined in two space groups as P21/c (standard choice) and P21/n (non-standard choice). The refined lattice parameters for the standard choice are a = 5.1505 (2), b = 7.2571 (2), c = 8.0264 (3) Šand ß = 125.571 (3)°, and for the non-standard choice are a = 5.1505 (2), b = 7.2571 (2), c = 6.5464 (2) Šand ß = 94.217 (3)°. All parameters for MgCoGa2 refined to R1 = 0.027 and wR2 = 0.042 using 594 reflections. The crystal structure peculiarities of this compound are discussed. Particular attention has been given to relationships with other similar structures, such as YPd2Si and Fe3C. Crystallographic analysis, together with linear muffin-tin orbital electronic structure calculations, reveals the presence of three-dimensional polyatomic nets with partial covalent bonding between the Ga atoms.

Synthesis, crystal structure and Hirshfeld surface analysis of N-(4-chloro-phen-yl)-5-cyclo-propyl-1-(4-meth-oxy-phen-yl)-1H-1,2,3-triazole-4-carboxamide.

The title compound, C19H17ClN4O2, was obtained via a two-step synthesis involving the enol-mediated click Dimroth reaction of 4-azido-anisole with methyl 3-cyclo-propyl-3-oxo-propano-ate leading to the 5-cyclo-propyl-1-(4-meth-oxy-phen-yl)-1H-1,2,3-triazole-4-carb-oxy-lic acid and subsequent acid amidation with 4-chloro-aniline by 1,1'-carbonyl-diimidazole (CDI). It crystallizes in space group P21/n, with one mol-ecule in the asymmetric unit. In the extended structure, two mol-ecules arranged in a near coplanar fashion relative to the triazole ring planes are inter-connected by N-H⋯N and C-H⋯N hydrogen bonds into a homodimer. The formation of dimers is a consequence of the above inter-action and the edge-to-face stacking of aromatic rings, which are turned by 58.0 (3)° relative to each other. The dimers are linked by C-H⋯O inter-actions into ribbons. DFT calculations demonstrate that the frontier mol-ecular orbitals are well separated in energy and the HOMO is largely localized on the 4-chloro-phenyl amide motif while the LUMO is associated with aryl-triazole grouping. A Hirshfeld surface analysis was performed to further analyse the inter-molecular inter-actions.

ß-Li2Zn5: A Low Symmetric Polar Intermetallic Compound.

The crystal structure of the high-temperature modification of the compound Li2Zn5 was determined using single-crystal X-ray diffraction data. It is the first representative of a new binary structure type with triclinic space group P1̅, where the parameters of the unit cell are a = 8.0073(3)Å, b = 11.5956(6)Å, c = 15.2956(5)Å, α = 96.39°, ß = 101.92°, and γ = 108.13°, the formula sum is Li11.748Zn31.113, Z = 2, and CCDC deposit number is 1861780. The title compound has a pseudohexagonal motif, made of 7- and 17-atom Li-zigzag chains and continuous Zn-chains, with the the relative placement of these large aggregates violating hexagonal symmetry. The structure may be decomposed into fragments, related to the AlB2 structure type, and could be obtained from multiplication of the unit cell, multiple substitution of Li atoms by triangles of Zn, insertion of Zn atoms, and deformation. Most structures of Li-Zn compounds, except LiZn, are highly symmetric but disordered. The possible causes of lower symmetry of ß-Li2Zn5 were analyzed using the results of DFT calculations. ß-Li2Zn5 shows high polarity of bonds, and Li atoms donate part of the electron density to Zn atoms.

Li20Mg6Cu13Al42: a new ordered quaternary superstructure to the icosahedral T-Mg32(Zn,Al)49 phase with fullerene-like Al60 cluster.

The new quaternary aluminide Li20Mg6Cu13Al42 was synthesized from the elements in a sealed tantalum crucible. The crystal structure was studied by single crystal and confirmed by X-ray powder diffraction. Li20Mg6Cu13Al42 {cI162, Im{\overline 3}, a = 13.8451 (2), R[F2 > 2σ(F2)] = 0.023} crystallizes as an ordered version of Mg32(Al,Zn)49 and Li-Cu-X (X = Al, Ga, Si) periodic crystals containing icosahedral clusters. The Li20Mg6Cu13Al42 structure can also be described as three-shell icosahedral clusters of [CuAl12@Li20Cu12@Al60], enclosed inside a distorted triacontahedron. The electronic structure calculations were performed by means of the TB-LMTO-ASA program and confirm the core-shell packing of these clusters. The isostructural compound of Li20Mg6Cu13Ga42 was found in a Li-Mg-Cu-Ga quaternary system.

New quaternary carbide Mg1.52Li0.24Al0.24C0.86 as a disorder derivative of the family of hexagonal close-packed (hcp) structures and the effect of structure modification on the electrochemical behaviour of the electrode.

Magnesium alloys are the basis for the creation of light and ultra-light alloys. They have attracted attention as potential materials for the accumulation and storage of hydrogen, as well as electrode materials in metal-hydride and magnesium-ion batteries. The search for new metal hydrides has involved magnesium alloys with rare-earth transition metals and doped by p- or s-elements. The synthesis and characterization of a new quaternary carbide, namely dimagnesium lithium aluminium carbide, Mg1.52Li0.24Al0.24C0.86, belonging to the family of hexagonal close-packed (hcp) structures, are reported. The title compound crystallizes with hexagonal symmetry (space group P-6m2), where two sites with -6m2 symmetry and one site with 3m. symmetry are occupied by an Mg/Li statistical mixture (in Wyckoff position 1a), an Mg/Al statistical mixture (in position 1d) and C atoms (2i). The cuboctahedral coordination is typical for Mg/Li and Mg/Al, and the C atom is enclosed in an octahedron. Electronic structure calculations were used for elucidation of the ability of lithium or aluminium to substitute magnesium, and evaluation of the nature of the bonding between atoms. The presence of carbon in the carbide phase improves the corrosion resistance of the Mg1.52Li0.24Al0.24C0.86 alloy compared to the ternary Mg1.52Li0.24Al0.24 alloy and Mg.

LiBC3: a new borocarbide based on graphene and heterographene networks.

Li-B-C alloys have attracted much interest because of their potential use in lithium-ion batteries and superconducting materials. The formation of the new compound LiBC3 [lithium boron tricarbide; own structure type, space group P-6m2, a = 2.5408 (3) Šand c = 7.5989 (9) Å] has been revealed and belongs to the graphite-like structure family. The crystal structure of LiBC3 presents hexagonal graphene carbon networks, lithium layers and heterographene B/C networks, alternating sequentially along the c axis. According to electronic structure calculations using the tight-binding linear muffin-tin orbital-atomic spheres approximations (TB-LMTO-ASA) method, strong covalent B-C and C-C interactions are established. The coordination polyhedra for the B and C atoms are trigonal prisms and for the Li atoms are hexagonal prisms.

Li9Al4Sn5 as a new ordered superstructure of the Li13Sn5 type.

Alloys from the ternary Li-Al-Sn system have been investigated with respect to possible applications as negative electrode materials in Li-ion batteries. This led to the discovery of a new ternary compound, a superstructure of the Li13Sn5 binary compound. The ternary stannide, Li9Al4Sn5 (nonalithium tetraaluminium pentastannide; trigonal, P-3m1, hP18), crystallizes as a new structure type, which is an ordered variant of the binary Li13Sn5 structure type. One Li and one Sn site have -3m. symmetry, and all other atoms occupy sites of 3m. symmetry. The polyhedra around all types of atoms are rhombic dodecahedra. The electronic structure was calculated by the tight-binding linear muffin-tin orbital atomic spheres approximation method. The electron concentration is higher around the Sn and Al atoms, which form an [Al4Sn5]m- polyanion.

Li4Ge2B as a new derivative of the Mo2B5 and Li5Sn2 structure types.

Binary and multicomponent intermetallic compounds based on lithium and p-elements of Groups III-V of the Periodic Table are useful as modern electrode materials in lithium-ion batteries. However, the interactions between the components in the Li-Ge-B ternary system have not been reported. The structure of tetralithium digermanium boride, Li4Ge2B, exhibits a new structure type, in the noncentrosymmetric space group R3m, in which all the Li, Ge and B atoms occupy sites with 3m symmetry. The title structure is closely related to the Mo2B5 and Li5Sn2 structure types, which crystallize in the centrosymmetric space group R-3m. All the atoms in the title structure are coordinated by rhombic dodecahedra (coordination number = 14), similar to the atoms in related structures. According to electronic structure calculations using the tight-binding-linear muffin-tin orbital-atomic spheres approximation (TB-LMTO-ASA) method, strong covalent Ge-Ge and Ge-B interactions were established.