Gray Arsenic Research Articles

Structural Transition in Layered As(1-x)P(x) Compounds: A Computational Study.

As a way to further improve the electronic properties of group V layered semiconductors, we propose to form in-layer 2D heterostructures of black phosphorus and gray arsenic. We use ab initio density functional theory to optimize the geometry, determine the electronic structure, and identify the most stable allotropes as a function of composition. Because pure black phosphorus and pure gray arsenic monolayers differ in their equilibrium structure, we predict a structural transition and a change in frontier states, including a change from a direct-gap to an indirect-gap semiconductor, with changing composition.

Strain-induced metal-semiconductor transition in monolayers and bilayers of gray arsenic: A computational study

We study the equilibrium geometry and electronic structure of thin films of layered gray arsenic using ab initio density functional theory. In contrast to bulk gray As that is semimetallic, thin films display a significant band gap that depends sensitively on the number of layers, in-layer strain, layer stacking, and interlayer spacing. We find that metallic character can be introduced by increasing the number of layers beyond two or by subjecting semiconducting monolayers and bilayers to moderate tensile strain. The strain-induced metal-semiconductor transition is triggered by changes in the band ordering near the top of the valence band that causes an abrupt change from $\ensuremath{\sigma}$ to $\ensuremath{\pi}$ character of the frontier states.

Two-dimensional arsenic monolayer sheet predicted from first-principles**Projected supported by the Henan Joint Funds of the National Natural Science Foundation of China (Grant Nos. U1304612 and U1404608), the National Natural Science Foundation of China (Grant Nos. 51374132 and 11404175), the Special Fund for Theoretical Physics of China (Grant No. 11247222), and Nanyang Normal University Science Foundation, China (Grant Nos. ZX2012018 and

Using first-principles calculations, we investigate the two-dimensional arsenic nanosheet isolated from bulk gray arsenic. Its dynamical stability is confirmed by phonon calculations and molecular dynamics analyzing. The arsenic sheet is an indirect band gap semiconductor with a band gap of 2.21 eV in the hybrid HSE06 functional calculations. The valence band maximum (VBM) and the conduction band minimum (CBM) are mainly occupied by the 4p orbitals of arsenic atoms, which is consistent with the partial charge densities of VBM and CBM. The charge density of the VBM G point has the character of a π bond, which originates from p orbitals. Furthermore, tensile and compressive strains are applied in the armchair and zigzag directions, related to the tensile deformations of zigzag and armchair nanotubes, respectively. We find that the ultimate strain in zigzag deformation is 0.13, smaller than 0.18 of armchair deformation. The limit compressive stresses of single-layer arsenic along armchair and zigzag directions are −4.83 GPa and −4.76 GPa with corresponding strains of −0.15 and −0.14, respectively.

Arsenene: Two-dimensional buckled and puckered honeycomb arsenic systems

Recently, phosphorene, a monolayer honeycomb structure of black phosphorus, was experimentally manufactured and has attracted rapidly growing interest. Motivated by phosphorene, here we investigate the stability and electronic properties of the honeycomb structure of the arsenic system based on first-principles calculations. Two types of honeycomb structures, buckled and puckered, are found to be stable. We call them arsenenes, as in the case of phosphorene. We find that both buckled and puckered arsenenes possess indirect gaps. We show that the band gap of puckered and buckled arsenenes can be tuned by applying strain. The gap closing occurs at 6% strain for puckered arsenene, where the bond angles between the nearest neighbors become nearly equal. An indirect-to-direct gap transition occurs by applying strain. Specifically, 1% strain is enough to transform puckered arsenene into a direct-gap semiconductor. We note that a bulk form of arsenic called gray arsenic exists which can be used as a precursor for buckled arsenene. Our results will pave the way for applications to light-emitting diodes and solar cells.

Crystal structure, spectroscopic properties, and magnetic behavior of the fluoride-derivatized lanthanoid(III) ortho-oxomolybdates(VI) LnF[MoO 4] ( Ln=Sm–Tm)

The fluoride-derivatized lanthanoid(III) ortho-oxomolybdates(VI) LnF[MoO 4] ( Ln=Sm–Tm) crystallize in the monoclinic space group P2 1/ c with four formula units per unit cell ( a=516–528 pm, b=1220–1248 pm, c=659–678 pm, β=112.5–113.1°). The structure contains one crystallographically unique Ln 3+ cation surrounded by two fluoride and six oxide anions in a square antiprism (CN=8). The square antiprisms [ LnF 2O 6] are interconnected via three edges to form layers ∞ 2 { [ Ln F 2 / 2 e O 4 / 2 e O 2 / 1 t ] 6 - } parallel (010), which are cross-linked along [010] by Mo 6+ in tetrahedral oxygen coordination to form the three-dimensional crystal structure. The fluoride anions within this arrangement exhibit a twofold coordination of Ln 3+ cations in the shape of a boomerang, which is connected to another F − anion to form planar [F 2 Ln 2] 4+ rhombuses. Magnetic measurements for GdF[MoO 4], TbF[MoO 4], and DyF[MoO 4] show Curie–Weiss behavior, despite the peculiar arrangement of the lanthanoid(III) cations in layers comparable with those of gray arsenic. Furthermore, Raman, infrared, and diffuse reflectance spectroscopy data for these compounds were recorded and interpreted.

A second-order effect causing the layer structure of arsenic

The role of second-order perturbations in the interlayer interactions of gray arsenic is discussed. A hypothetical structural change from the germanium (or diamond) to the arsenic structures is considered using a two-layer model in terms of second-order Jahn–Teller distortions. We show from the concept of transition density or transition force that the second-order term originating from mixing of the pseudodegenerate bands near the Fermi level leads to the well-known layer structure of arsenic. The interesting structure of arsenic is a consequence of orbital interactions near the Fermi level.

Synthesis and thermolysis of di- and triarsenic complexes of chromium. Crystal structure of [CpCr(CO)2]2As2

The cothermolysis of [CpCr(CO) 3 ] 2 (Cp=η 5 -C 5 H 5 ) with excess gray arsenic in refluxing toluene for 1-1.5 h resulted in the isolation of Cp 2 Cr 2 (CO) 4 (μ-η 2 -As 2 ), CpCr(CO) 2 (η 3 -As 3 ), Cp 2 Cr 2 (CO) 4 (Cr≡Cr) and Cp 2 Cr 2 AsO 5 in 20.4, 14.2, 5.3, and 13.6% yields, respectively. The reaction when extended to 16 h gave 3, Cp 2 Cr 2 As 5 , and Cp 5 Cr 5 As 4 O 8 in 5, 22, 39, and 8% yields, respectively

Complexes with Substituent‐free Acyclic and Cyclic Phosphorus, Arsenic, Antimony, and Bismuth Ligands

AbstractUntil recently, phosphorus, arsenic, antimony and bismuth ligands were nearly always understood to be molecules such as R3E, R2E(CH2)nER2, and RC[(CH2)nER2]3(E = P, As, Sb, Bi) in which the lone pair of the atom E functions as a 2e donor. Current research interests, however, increasingly involve substituent‐free En ligands (n = 1–6), the various types of which are mainly accessible via EX3 (X = F,Cl,Br,Ph), E (SiMe3)3, (RAs)n, P4S3, As4S4, gray arsenic, and especially P4 and As4; these ligands can be stabilized in the coordination spheres of certain transition metal fragments. P1, As1 and Sb1 units with multiple M‐E bonds are found in bi‐ and trinuclear complexes; E1 units can also be encapsulated (partially or completely) in cavities of a variety of metal cluster frameworks. Metallatetrahedranes with up to three E atoms are especially common. Besides E1 units, the greatest variety of coordination modes is exhibited by E4 ligands, which are found as intact tetrahedra and also as parts of chains, polycycles, cubes and a trigonal prism. The phosphorus and arsenic species cyclo‐En, isoelectronic to the carbocyclic (CH)n species, are suitable ligands for forming sandwich complexes (n =3, 4, 5) and triple‐decker sandwich complexes (n = 3, 5, 6). In addition to the wide variety of chemical reactions, remarkable parallels are found in organic chemistry as well as in solid‐state chemistry for many of these substance classes. Some of the molecules have received lively interest from theoretical chemists.