Polymeric Fused-Ring Type Iron Phthalocyanine Nanosheet and Its Derivative Ribbons and Tubes

On the basis of density functional theory calculations, we study the electronic and magnetic properties of an iron phthalocyanine (FePc) nanosheet (FePcNST) and its derivatives, nanoribbons (FePcNRs) and nanotubes (FePcNTs). The GGA+<i>U</i>+SOC calculations reveal that the interesting in-plane magnetic anisotropy comes from unquenched in-plane orbital moments for FePcNST. The calculations indicate that the most stable antiferromagnetic (AFM) ordering for FePcNRs is G-type AFM, which is independent of the ribbon width. In addition, FePcNTs with radii larger than 10 Å are thermodynamically and thermally stable and can be rolled up from the FePcNST with only several millielectronvolts energy cost. Interestingly, the most stable AFM types of FePcNTs highly depend on the number of Fe ions (odd or even) on the circumference. These results may shed useful light on further experimental and theoretical studies on the organometallic nanosheet and its one-dimensional derivatives

PbMnIn₂S₅: Synthesis, Structure, and Properties

The first manganese member in a Pb–M–In–Q system, PbMnIn₂S₅, has been discovered by a high-temperature solid-state reaction. It adopts a Sr₂Tl₂O₅ structure type in orthorhombic space group <i>Cmcm</i> (No. 63) with <i>a</i> = 3.896(2) Å, <i>b</i> = 12.731(7) Å, <i>c</i> = 15.770(9) Å, and <i>Z</i> = 1. The structure consists of corrugated layers made by (In1/Mn1)­S₆ octahedra that are further interconnected by chains of edge-sharing (In2/Mn2)­S₆ octahedra into a three-dimensional framework; Pb²⁺ cations are coordinated in PbS₈ bicapped triangular prisms that are face-shared along the <i>a</i> direction. The crystallographically distinguished octahedrally coordinated 8<i>f</i> and 4<i>b</i> sites are disordered by Mn and In atoms. Such a structure allows antiferromagnetic interactions between the high-spin Mn²⁺ anions. The optical band gap is measured to be about 1.45 eV

Polymeric Fused-Ring Type Iron Phthalocyanine Nanosheet and Its Derivative Ribbons and Tubes

On the basis of density functional theory calculations, we study the electronic and magnetic properties of an iron phthalocyanine (FePc) nanosheet (FePcNST) and its derivatives, nanoribbons (FePcNRs) and nanotubes (FePcNTs). The GGA+<i>U</i>+SOC calculations reveal that the interesting in-plane magnetic anisotropy comes from unquenched in-plane orbital moments for FePcNST. The calculations indicate that the most stable antiferromagnetic (AFM) ordering for FePcNRs is G-type AFM, which is independent of the ribbon width. In addition, FePcNTs with radii larger than 10 Å are thermodynamically and thermally stable and can be rolled up from the FePcNST with only several millielectronvolts energy cost. Interestingly, the most stable AFM types of FePcNTs highly depend on the number of Fe ions (odd or even) on the circumference. These results may shed useful light on further experimental and theoretical studies on the organometallic nanosheet and its one-dimensional derivatives

New Facile Method for the Preparation of M₃B₇O₁₃I Boracites (M = Mn, Fe, Co, Ni, Cd)

Five iodine boracites, M₃B₇O₁₃I (M = Mn, Fe, Co, Ni, Cd), have been synthesized by reactions of metal oxide, B₂O₃, element B, and I₂ at intermediate temperature above 350 °C. Powder X-ray diffraction analyses verify the identities and purity of the products, which are also confirmed by magnetic property measurement. Except safe, cheap, and convenient, this novel method is significantly flexible in the selection of the starting metal oxide. The influence of the reaction temperature and time has also been studied

Polymeric Fused-Ring Type Iron Phthalocyanine Nanosheet and Its Derivative Ribbons and Tubes

On the basis of density functional theory calculations, we study the electronic and magnetic properties of an iron phthalocyanine (FePc) nanosheet (FePcNST) and its derivatives, nanoribbons (FePcNRs) and nanotubes (FePcNTs). The GGA+<i>U</i>+SOC calculations reveal that the interesting in-plane magnetic anisotropy comes from unquenched in-plane orbital moments for FePcNST. The calculations indicate that the most stable antiferromagnetic (AFM) ordering for FePcNRs is G-type AFM, which is independent of the ribbon width. In addition, FePcNTs with radii larger than 10 Å are thermodynamically and thermally stable and can be rolled up from the FePcNST with only several millielectronvolts energy cost. Interestingly, the most stable AFM types of FePcNTs highly depend on the number of Fe ions (odd or even) on the circumference. These results may shed useful light on further experimental and theoretical studies on the organometallic nanosheet and its one-dimensional derivatives

Six New Members of the A₂M^IIM^IV₃Q₈ Family and Their Structural Relationship

The A₂M^IIM^IV₃Q₈ family (A = alkali metal; M^II = divalent metal; M^IV = tetravalent metal; Q = chalcogenide) has attracted much attention because of its diverse structures and properties. Herein, we have successfully synthesized six new compounds as the first Mn-containing members of this family, Cs₂MnGe₃S₈ (<b>1</b>), Cs₂MnGe₃Se₈ (<b>2</b>), Cs₂MnSn₃Se₈ (<b>3</b>), Rb₂MnGe₃S₈ (<b>4</b>), Rb₂MnGe₃Se₈ (<b>5</b>), and Rb₂MnSn₃Se₈ (<b>6</b>). Compounds <b>1</b> and <b>6</b> crystallize in the monoclinic space group <i>P</i>2₁/<i>n</i> (No. 14) and <i>P</i>2₁ (No. 4), respectively, whereas compounds <b>2</b>–<b>5</b> crystallize in the non-centrosymmetric orthorhombic <i>P</i>2₁2₁2₁ (No. 19). According to our theoretical calculations, their energy gaps are mainly dominated by s states of M^IV and p states of Q and minor Mn 3d. Plate-like crystals with sizes about 20 × 5 × 1 mm³ of <b>2</b> and <b>3</b> are obtained by the Bridgeman method. In addition, we propose a structure mismatch factor that is defined as <i>F</i> = <i>r</i>_M^_II+ <i>r</i>_M^_IV + 2<i>r</i>_Q^_2– – 2<i>r</i>_A^₊ to provide a clear description of how three different structure types distribute among the A₂M^IIM^IV₃Q₈ family; when 1.2 < <i>F</i> < 1.9, members will adopt a <i>P</i>2₁2₁2₁-type structure; when <i>F</i> is too small (<1.2) or too large (>1.9), <i>P</i>2₁/<i>n</i> or <i>P</i>2₁-type, respectively, will be taken

Ba₆Zn₇Ga₂S₁₆: A Wide Band Gap Sulfide with Phase-Matchable Infrared NLO Properties

High-performance infrared (IR) nonlinear optical (NLO) materials with large laser damage thresholds (LDTs) are urgently needed because the current commercially available AgGaS₂, AgGaSe₂, and ZnGeP₂ suffer their very low LDTs which shorten significantly their service lifetimes. Here, a novel sulfide, Ba₆Zn₇Ga₂S₁₆ with a very wide band gap of 3.5 eV, has been discovered. This compound crystallizes in the chiral trigonal <i>R</i>3 space group with a novel 3D framework that is constructed by ZnS₄ tetrahedra, Zn₃GaS₁₀ supertetrahedra (a T2-type), and Zn₃GaS₁₀ quadri-tetrahedral clusters via vertex-sharing. Such a novel structure exhibits desirable features which suggest a promising NLO material: phase-matchability (PM), good NLO efficiency (about half that of benchmark AgGaS₂), and the highest LDT among PM chalcogenides (28 times that of benchmark AgGaS₂). In addition, the density functional theory (DFT) calculations confirm its PM behavior and reveal that the second harmonic generation (SHG) origin is mainly ascribed to the transition process from S-3p to Ga-4p, Zn-3p, Zn-3d, and Ba-5d states; the calculated <i>d</i>₁₁ coefficient of 6.1 pm/V agrees well with experimental values

SiC₂ Siligraphene and Nanotubes: Novel Donor Materials in Excitonic Solar Cells

In excitonic solar cells (XSC), power conversion efficiency (PCE) depends critically on the interface band alignment between donor and acceptor materials. Graphene or silicene is not suitable for donor materials due to their semimetallic features (zero band gaps); it is therefore highly desired to open an energy gap in graphene or silicene to extend their application in optoelectronic devices, especially in photovoltaics. In this paper, based on the global particle-swarm optimization algorithm and the density functional theory methods, we predict a novel SiC₂ siligraphene (g-SiC₂) with a direct band gap of 1.09 eV showing infinite planar geometry, in which Si and C atoms adopt sp² hybridization and C atoms form delocalized 4 C-domains that are periodically separated by Si atoms. Such a g-SiC₂ siligraphene (with a global minimum of energy) is 0.41 eV/atom lower and thermally stabler than the isomeric pt-SiC₂ silagraphene containing planar 4-fold coordinated silicon (3000 K vs 1000 K). Interestingly, the derivative (<i>n</i>, 0), (<i>n</i>, <i>n</i>) nanotubes (with diameters greater than 8.0 Å) have band gaps about 1.09 eV, which are independent of the chirality and diameter. Besides, a series of g-SiC₂/GaN bilayer and g-SiC₂ nanotube/ZnO monolayer XSCs have been proposed, which exhibit considerably high PCEs in the range of 12–20%

First-Principles Study of Lithium Adsorption and Diffusion on Graphene with Point Defects

To understand the effect of point defects on the Li adsorption on graphene, we have studied the adsorption and diffusion of lithium on graphene with divacancy and Stone–Wales defect using the first-principles calculations. Our results show that in the presence of divacancy Li adatom energetically prefers the hollow site above the center of an octagonal ring rather than the top sites of carbon atoms next to vacancy site. In the case of Stone–Wales defect, Li atom is energetically favorable to be adsorbed on the top site of carbon atom in a pentagonal ring shared with two hexagonal rings, and such adsorption results in a bucking of graphene sheet. For divacancy and Stone–Wales defects in graphene, their interactions with a Li adatom are attractive, suggesting that the presence of point defects would enhance the Li adsorption on graphene. The difference charge density and the Bader charge analysis both show that there is a significant charge transfer from Li adatom to it nearest neighbor carbon atoms

Synthesis and Shape Control of Ag₈SnS₆ Submicropyramids with High Surface Energy

Orthorhombic Ag₈SnS₆ submicropyramids with high surface energy have been synthesized by the solventless method. The four outer surfaces are (4̅11), (112), (211̅) and (41̅3) lattice planes according to scanning electron microscopy, transmission electron microscopy, high resolution TEM, fast Fourier transform analyses, and angle measurements. Such morphology agrees well with the crystallographic symmetry requirement of the space group <i>Pna</i>2₁ of orthorhombic Ag₈SnS₆. Effects of polar washing solvent, reaction temperature, and time that influence the morphology are systematically investigated. Interestingly, the as-synthesized Ag₈SnS₆ submicropyramids exhibit superior photocatalytic activity to commercial P25 TiO₂ under visible light, which may owe to the high surface energy