As-As Bond Research Articles

Electronic State of Arsenic <i>endo</i>-atom and indices of interatomic bonds in[As@Ni<sub>12</sub>As<sub>20</sub>]<sup>3-/0</sup>, As<sub>20</sub>, Ni<sub>12</sub>As<sub>20</sub>, As@C<sub>60</sub>, and As@C<sub>70</sub> Clusters

The DFT PBE0/SDD method was used to calculate bond lengths and bond indices in As20, Ni12As20, [As@Ni12As20]3-, As@C60 and As@C70 clusters. The degrees of oxidation and reduction of the endo -atom and the shell are expressed in terms of the populations of one-electron states localized in these components of the complexes. Each As atom in clusters has a entirely localized lone electron pair. The arsenic atom inside fullerenes retains the electronic configuration and spin of the ground state of the free As atom. Inside the [Ni12As20]6- shell, it has an oxidation state of 3+. There is no covalent bond between the endo -atom and the shell in clusters. The bond indices refute the opinion about the “onion” structure of [As@Ni12@As20]3-: the nickel atoms are not bonded to each other, the As-As bond indices are three times lower than in As20.

Wave functions, electronic localization, and bonding properties for correlated materials beyond the Kohn-Sham formalism

Many-body theories such as dynamical mean field theory (DMFT) have enabled the description of the electron-electron correlation effects that are missing in current density functional theory (DFT) calculations. However, there has been relatively little focus on the wave functions from these theories. We present the methodology of the newly developed elk-triqs interface and how to calculate the DFT with DMFT ($\mathrm{DFT}+\mathrm{DMFT}$) wave functions, which can be used to calculate $\mathrm{DFT}+\mathrm{DMFT}$ wave-function-dependent quantities. We illustrate this by calculating the electron localization function (ELF) in monolayer ${\mathrm{SrVO}}_{3}$ and ${\mathrm{CaFe}}_{2}{\mathrm{As}}_{2}$, which provides a means of visualizing their chemical bonds. Monolayer ${\mathrm{SrVO}}_{3}$ ELFs are sensitive to the charge redistribution between the DFT, one-shot $\mathrm{DFT}+\mathrm{DMFT}$, and fully charge self-consistent $\mathrm{DFT}+\mathrm{DMFT}$ calculations. In both tetragonal and collapsed tetragonal ${\mathrm{CaFe}}_{2}{\mathrm{As}}_{2}$ phases, the ELF changes weakly with correlation-induced charge redistribution of the hybridized As $p$ and Fe $d$ states. Nonetheless, the interlayer As-As bond in the collapsed tetragonal structure is robust to the changes at and around the Fermi level.

Anomalous Dome-like Superconductivity in RE2(Cu1-xNix)5As3O2 (RE = La, Pr, Nd)

SummaryA significant manifestation of interplay of superconductivity and charge density wave, spin density wave, or magnetism is a dome-like superconducting critical temperature (Tc) in cuprate, iron-based, and heavy Fermion superconductors. Pesudogap, quantum critical point, and strange metals emerge in different doping ranges. Exploring dome-like Tc in new superconductors is of interest to detect emergent effects. Here we report the superconductivity in a new layered Cu-based compound RE2Cu5As3O2 (RE = La, Pr, Nd), in which the Tc exhibits dome-like variation with a maximum Tc of 2.5, 1.2, and 1.0 K with substitution of Cu by large amount of Ni ions. Simultaneously, the structural parameters like As-As bond length and c/a ratio exhibit unusual variations as the Ni-doping level goes through the optimal value. The robustness of superconductivity, up to 60% of Ni doping, reveals the unexpected impurity effect on inducing and enhancing superconductivity in these novel layered materials.

Collapsed tetragonal phase as a strongly covalent and fully nonmagnetic state: Persistent magnetism with interlayer As–As bond formation in Rh-doped Ca0.8Sr0.2Fe2As2

A well-known feature of CaFe$_{2}$As$_{2}$-based superconductors is the pressure-induced collapsed tetragonal phase that is commonly ascribed to the formation of an interlayer As-As bond. Using detailed X-ray scattering and spectroscopy, we find that Rh-doped Ca$_{0.8}$Sr$_{0.2}$Fe$_{2}$As$_{2}$ does not undergo a first-order phase transition and that local Fe moments persist despite the formation of interlayer As-As bonds. Our density functional theory calculations reveal that the Fe-As bond geometry is critical for stabilizing magnetism and that the pressure-induced drop in the $c$ lattice parameter observed in pure CaFe$_{2}$As$_{2}$ is mostly due to a constriction within the FeAs planes. These phenomena are best understood using an often overlooked explanation for the equilibrium Fe-As bond geometry, which is set by a competition between covalent bonding and exchange splitting between strongly hybridized Fe $3d$ and As $4p$ states. In this framework, the collapsed tetragonal phase emerges when covalent bonding completely wins out over exchange splitting. Thus the collapsed tetragonal phase is properly understood as a strong, covalent phase that is fully nonmagnetic with the As-As bond forming as a byproduct.

Molecular Polyarsenides of the Rare-Earth Elements.

Reduction of [Cp*Fe(η(5)-As5)] with [Cp''2Sm(thf)] (Cp''=η(5)-1,3-(tBu)2C5H3) under various conditions led to [(Cp''2Sm)(μ,η(4):η(4)-As4)(Cp*Fe)] and [(Cp''2Sm)2As7(Cp*Fe)]. Both compounds are the first polyarsenides of the rare-earth metals. [(Cp''2Sm)(μ,η(4):η(4)-As4)(Cp*Fe)] is also the first d/f-triple decker sandwich complex with a purely inorganic planar middle deck. The central As4(2-) unit is isolobal with the 6π-aromatic cyclobutadiene dianion (CH)4(2-). [(Cp''2Sm)2As7(Cp*Fe)] contains an As7(3-) cage, which has a norbornadiene-like structure with two short As-As bonds in the scaffold. DFT calculations confirm all the structural observations. The As-As bond order inside the cyclo As4 ligand in [(Cp''2Sm)(μ,η(4):η(4)-As4)(Cp*Fe)] was estimated to be in between an As-As single bond and a formally aromatic As4(2-) system.

In situ investigations of laser and thermally modified As2S3 nanolayers: Synchrotron radiation photoelectron spectroscopy and density functional theory calculations

As-deposited, annealed, and in situ As2S3 nanolayers, illuminated by blue (405 nm) and red (650 nm) laser light, were studied using synchrotron radiation photoelectron spectroscopy and DFT electronic structure calculations. Changes in composition and local atomic coordination occurring in the irradiated region of As2S3 films were monitored by analysis of As 3d and S 2p core levels. These studies show that both the thermal treatment and the red laser illumination of As2S3 nanolayers decrease the concentration of homopolar (As-As and S-S) bonds. From the other hand, an increasing concentration of As-rich structural units (s.u.) with a homopolar As-As bond was observed under in situ blue laser illumination of As2S3 nanolayers. Molecular orbital energies were calculated for different As- and S-centered s.u. and used for the interpretation of the core levels and valence band spectra. The surface local structure of the As2S3 nanolayers and its photoinduced transformation are discussed in detail.

Pressure-induced collapsed-tetragonal phase inSrCo2As2

We present high-energy x-ray diffraction data under applied pressures up to $p=29\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, neutron diffraction measurements up to $p=1.1\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, and electrical resistance measurements up to $p=5.9\phantom{\rule{0.16em}{0ex}}\mathrm{GPa}$, on ${\mathrm{SrCo}}_{2}{\mathrm{As}}_{2}$. Our x-ray diffraction data demonstrate that there is a first-order transition between the tetragonal (T) and collapsed-tetragonal (cT) phases, with an onset above approximately 6 GPa at $T=7\phantom{\rule{0.16em}{0ex}}\mathrm{K}$. The pressure for the onset of the cT phase and the range of coexistence between the T and cT phases appears to be nearly temperature independent. The compressibility along the $a$ axis is the same for the T and cT phases, whereas, along the $c$ axis, the cT phase is significantly stiffer, which may be due to the formation of an As-As bond in the cT phase. Our resistivity measurements found no evidence of superconductivity in ${\mathrm{SrCo}}_{2}{\mathrm{As}}_{2}$ for $p\ensuremath{\le}5.9$ GPa and $T\ensuremath{\ge}1.8$ K. The resistivity data also show signatures consistent with a pressure-induced phase transition for $p \ensuremath{\gtrsim}5.5$ GPa. Single-crystal neutron diffraction measurements performed up to 1.1 GPa in the T phase found no evidence of stripe-type or A-type antiferromagnetic ordering down to 10 K. Spin-polarized total-energy calculations demonstrate that the cT phase is the stable phase at high pressure with a $\frac{c}{a}$ ratio of 2.54. Furthermore, these calculations indicate that the cT phase of ${\mathrm{SrCo}}_{2}{\mathrm{As}}_{2}$ should manifest either A-type antiferromagnetic or ferromagnetic order.

Formation of As-As bond and its effect on absence of superconductivity in the collapsed tetragonal phase ofCa0.86Pr0.14Fe2As2: An optical spectroscopy study

The temperature dependence of in-plane optical conductivity has been investigated for ${\mathrm{Ca}}_{0.86}{\mathrm{Pr}}_{0.14}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$, which shows a structural transition from tetragonal (T) to collapsed tetragonal (cT) phase at ${T}_{cT}\ensuremath{\sim}73$ K. Upon entering the cT phase, drastic change characterized by the formation of a midinfrared peak near $3200 {\text{cm}}^{\ensuremath{-}1}$ (0.4 eV) in the optical conductivity is observed. Analysis of the spectral weight reveals reduced electron correlation after the cT phase transition. Based on the calculated band structure and simulated optical conductivity, we attribute the new feature around 0.4 eV to the formation of an interlayer As-As bond. The As-As bond strongly affects the Fe-As hybridizations and, in turn, drastically changes the ${\mathrm{Ca}}_{0.86}{\mathrm{Pr}}_{0.14}{\mathrm{Fe}}_{2}{\mathrm{As}}_{2}$ into a nonmagnetic Fermi liquid system without bulk superconductivity in the cT phase.

An End‐on‐Coordinated As4 Tetrahedron

One time only: The reaction of [Cp*Ru(dppe)Cl] with the potent As4 transfer reagent [Ag(η(2)-As4)2](+)[pftb](-) leads to [Cp*Ru(dppe)(η(1)-As4)](+)[pftb](-) with an unprecedented end-on-coordinated As4 tetrahedron. Reaction with a second cationic ruthenium complex fragment does not lead to a second end-on coordination but to the cleavage of one basal As-As bond. This behavior, which differs from its phosphorus analogues, is rationalized by DFT calculations.

Synthesis and Crystal Structure of K3AsSe4 and K4As2Se5 Containing [AsSe4]3- Anions and a Novel [As2Se5]4- Isomer Featuring an As–As Bond

Two novel selenoarsenates, K3AsSe4 and K4As2Se5, were synthesized by the mild solvothermal reaction of potassium carbonate and arsenic and selenium powder in the presence of superheated ethylenediamine and structurally characterized by single-crystal X-ray diffraction. K3AsSe4 crystallizes in the orthorhombic space group Pnma (no. 62) with a = 9:4169(4), b = 10:9695(5), c = 9:7568(8) Å, Z = 4 and V = 1007:86(10) Å3 and contains [AsSe4]3- anions with pentavalent arsenic. K4As2Se5 crystallizes in the monoclinic space group P21/n (no. 14) with a = 7:6167(2), b = 22:8733(4), c = 8:4687(2) Å, b = 107:241(2)°, Z = 4 and V = 1409:14(5) Å3, and shows isolated [As2Se5]4- anions. The most prominent feature of the latter anions is the presence of arsenic in two different formal oxidation states (+4/+2) due to the presence of an As-As bond.

Collapsed tetragonal phase in Ca(Fe1−xCox)2As2stabilized by pressure: Structural studies using single-crystal neutron diffraction

Ca(Fe${}_{1\ensuremath{-}x}$Co${}_{x}$)${}_{2}$As${}_{2}$ single crystals with concentration $x=0.032$, 0.051, and 0.063 were investigated by means of neutron diffraction under hydrostatic pressure. The region of existence of the high-temperature tetragonal, low-temperature orthorhombic, and pressure-induced collapsed tetragonal phases have been determined and the corresponding $p$-$T$ phase diagrams for the three compositions have been constructed. Structural details of the tetragonal phases at various conditions have been determined. The anomaly marking the orthorhombic-to-tetragonal structural phase transition temperature ${T}_{S}$ decreases with increasing Co substitution. Similarly to that, the critical pressure of the tetragonal (or orthorhombic)-to-collapsed-tetragonal transition also decreases with increasing Co doping level. The behavior is highly hysteretic and the differences in critical pressures with increasing and decreasing branches eventually makes the collapsed tetragonal phase stable down to ambient pressure and enables structural studies under identical conditions. Within the error bars on the fourth digit, no modification of the As structural positional parameter is found. Such a result suggests that the change of the As-As bond is caused solely by the reduction of the $c$-axis lattice parameter.

Symmetry-preserving lattice collapse in tetragonal SrFe2−xRuxAs2(x=0,0.2): A combined experimental and theoretical study

In a joint experimental and theoretical study, we investigate the isostructural collapse from the ambient pressure tetragonal phase to a collapsed tetragonal phase for non-superconducting metallic SrFe2As2 and SrFe_1.8Ru_0.2As_2. The crystallographic details have been studied using X-ray powder diffraction up to 20 GPa pressure in a diamond anvil cell. The structural phase transition occurs at 10 GPa and 9 GPa for SrFe2As2 and SrFe_1.8Ru_0.2As_2, respectively. The changes in the unit cell dimensions are highly anisotropic with a continuous decrease of the c lattice parameter with pressure, while the a-axis length increases until the transition to a collapsed tetragonal phase and then continues to decrease. Across the phase transition, we observe a volume reduction of 5% and 4% for SrFe2As2 and SrFe_1.8Ru_0.2As_2, respectively. We are able to discern that Ru substitution on the Fe-site acts like `chemical pressure' to the system. Density-functional theory-based calculations of the electronic structure and electron localizability indicator are consistent with the experimental observations. Detailed analysis of the electronic structure in k-space and real space reveals As 4pz interlayer bond formation as the driving force of the c/a collapse with a change in the As-As bond length of about 0.35ang.

Mechanistic variety in zirconium-catalyzed bond-forming reaction of arsines

Triamidoamine-supported zirconium complexes have been demonstrated to catalyze a range of bond-forming events utilizing arsines. Three different mechanisms have been observed in these reactions. In the first mechanism, triamidoamine-supported zirconium complexes of the general type (N3N)ZrX (N3N =N(CH2CH2NSiMe3)33-; X = monoanionic ligand) catalyzed the dehydrogenative dimerization of diphenylarsine. Mechanistic analysis revealed that As-As bond formation proceeds via sigma-bond metathesis steps similar to the previously reported dehydrocoupling of phosphines by the same catalysts. In the second mechanism, sterically encumbered primary arsines appear to be dehydrocoupled via alpha elimination of an arsinidene fragment. Dehydrocoupling of dmpAsH2 (dmp = 2,6-dimesitylphenyl) to form (dmp)As = As(dmp) by (N3N)Zr-complexes appeared to proceed via elimination of dmpAs: from the arsenido intermediate, (N3N)ZrAsH(dmp). Further support for -arsinidene elimination came from the thermal decomposition of (N3N)ZrAsHMes (9) to (MesAs)4 (10), which obeyed first-order kinetics. In the third mechanism, the observation of stoichiometric insertion reactivity of the Zr-As bond with polar substrates, PhCH2NC, PhCN, (1-napthyl)NCS, and CS2, led to the development of intermolecular hydroarsination catalysis of terminal alkynes. Here, (N3N)ZrAsPh2 (2) catalyzed the addition of diphenylarsine to phenylacetylene and 1-hexyne to give the respective vinylarsine products. Arsenido complexes 2 and 9 and tetraarsine 10 have been structurally characterized.

Wakabayashilite, [(As,Sb)6S9][As4S5]: Crystal structure, pseudosymmetry, twinning, and revised chemical formula

The crystal structure of the rare mineral wakabayashilite was solved by direct methods using intensity data collected from a twinned crystal. This study revealed that, in spite of the strong hexagonal pseudosymmetry, the structure is orthorhombic (space group Pna2 1 ) with a o = 25.262(1), b o = 14.563(1), c o = 6.492(1) Å, and V o = 2388.4(2) Å 3 . The refinement of an anisotropic model led to an R index of 6.08% for 3135 observed reflections [F o > 4σ(F o )] and 8.71% for all 4260 independent reflections. Wakabayashilite is twinned by reticular merohedry [twin plane (110)]. There are two structural units in the structure: (1) [M 6 S 9 ] bundle-like chains running along the [001] axis, consisting of corner-sharing MS 3 trigonal pyramids (M = As, Sb), and (2) rods of As 4 S 5 cage-like molecules, located in the space between three bundles and held together by van der Waals forces. The crystal chemical formula was therefore revised according to the structural results, yielding [(As,Sb) 6 S 9 ][As 4 S 5 ] (Z = 4). Both the intramolecular As-S and As-As bond distances and those within the bundle-like units match closely the values commonly observed in the molecule-formed structures of other arsenic sulfides and those found in orpiment, respectively. To contribute to the understanding of the effects of light exposure on the structure of the arsenic sulfides, the crystal was exposed to filtered polychromatic light. The unit-cell parameters were measured after each exposure. The results showed that the As 4 S 5 molecules do not undergo any transformations, as previously found by exposing uzonite to light.

Structures and electron affinities of the di‐arsenic fluorides As2Fn/As2F (n = 1–8)

Developments in the preparation of new materials for microelectronics are focusing new attention on molecular systems incorporating several arsenic atoms. A systematic investigation of the As2Fn/As2Fn- systems was carried out using Density Functional Theory methods and a DZP++ quality basis set. Global and low-lying local geometric minima and relative energies are discussed and compared. The three types of neutral-anion separations reported in this work are: the adiabatic electron affinity (EAad), the vertical electron affinity (EAvert), and the vertical detachment energy (VDE). Harmonic vibrational frequencies pertaining to the global minimum for each compound are reported. From the first four studied species (As2Fn, n=1-4), all neutral molecules and their anions are shown to be stable with respect to As-As bond breaking. The neutral As2F molecule and its anion are predicted to have Cs symmetry. We find the trans F-As-As-F isomer of C2h symmetry and a pyramidalized vinylidene-like As-As-F2- isomer of Cs symmetry to be the global minima for the As2F2 and As2F2- species, respectively. The lowest lying minima of As2F3 and As2F3- are vinyl radical-like structures F-As-As-F2 of Cs symmetry. The neutral As2F4 global minimum is a trans-bent (like Si2H4) F2-As-As-F2 isomer of C2 symmetry, while its anion is predicted to have an unusual fluorine-bridged (C(1)) structure. The global minima of the neutral As2Fn species, n=5-8, are weakly bound complexes, held together by dipole-dipole interactions. All such structures have the AsFm-AsFn form, where (m,n) is (2,3) for As2F5, (3,3) for As2F6, (4,3) for As2F7), and (5,3) for As2F8. For As2F8 the beautiful pentavalent F4As-AsF4 structure (analogous to the stable AsF5 molecule) lies about 30 kcal/mol above the AsF3 . . . AsF5 complex. The stability of AsF(5) depends crucially on the strong As-F bonds, and replacing one of these with an As-As bond (in F4As-AsF4) has a very negative impact on the molecule's stability. The anions As2Fn-, n=5-8, are shown to be stable with respect to the As-As bond breaking, and we predict that all of them have fluorine-bridged or fluorine-linked structures. The zero-point vibrational energy corrected adiabatic electron affinities are predicted to be 2.28 eV (As2F), 1.95 eV (As2F2), 2.39 eV (As2F3), 1.71 eV (As2F4), 2.72 eV (As2F5), 1.79 eV (As2F6), 5.26 eV (As2F7), and 3.40 eV (As2F8) from the BHLYP method. Vertical detachment energies are rather large, especially for species with fluorine-bridged global minima, having values up to 6.45 eV (As2F7, BHLYP).

Surface reconstruction and As-polymerization at fractured loellingite (FeAs2) surfaces

Synchrotron Radiation X-ray Photoelectron Spectroscopy (SRXPS) and conventional X-ray Photoelectron Spectroscopy (XPS) of pristine (unreacted) loellingite fracture surfaces reveal two distinct contributions to the As 3d spectrum. One is derived from As atoms of the bulk phase (fully coordinated As atoms) and the other is derived from polymeric As species located on fracture surfaces. Surface polymerization reactions probably proceed in response to fracture whereby As dimers at the surface react to produce surface tetramers and possibly surface heptamers. Trimeric and pentameric species may form where As-As bond scission occurs during fracture. The (001) surface of loellingite is autocompensated and unlikely to undergo reconstruction. The (010) and (100) surfaces are, however, arsenic-terminated and uncompensated, and surface reconstruction is expected. The short “c” dimension of the loellingite unit cell is critically important to surface polymerization because arsenic dimers on (100) and (010) surfaces are separated by 2.88 Å (normal to c) which is only 16% greater than the As-As bond length. Because of the short distance, adjacent surface dimers likely tilt toward each other and bond to produce surface tetramers. This should introduce minimal strain and eliminate high-energy dangling bonds thus stabilizing the surface. The polymerization reaction also explains the absence of surface (core-level-shifted) As dimeric and monomeric signals such as observed on pyrite surfaces

An isolated cyclo-tetraarsendiide: low temperature synthesis and crystal structure of bis-pentaamminesodium tetraarsendiide-ammonia (1/3) [Na(NH3)5]2As(4).3NH3.

Reduction of an excess of arsenic with a solution of sodium in liquid ammonia yields the thermally unstable title compound [Na(NH3)5]2As(4).3NH3, which contains isolated square-planar As4(2-) ions with a mean As-As bond length of 2,345 A.

Structural rearrangements in triple-decker-like complexes with mixed group 15/16 ligands: synthesis and characterization of the redox couple.

The reaction of As4Se4 with stoichiometric amounts of [Cp*Fe2(CO)4] (Cp* = C5Me5) in boiling toluene forms [Cp2*Fe2As2Se2] (1) in good yield. X-ray crystallography shows 1 to have a triple-decker structure which comprises a tetraatomic mu,eta4:4-As2Se2 ligand. Density functional theory (DFT) and extended Hückel molecular orbital (EHMO) calculations confirm that the As2Se2 ligand behaves as a four-electron pi donor. Oxidation of 1 with equimolar amounts of [(C5H5)2Fe]PF6, Br2 and I2, respectively, gave compounds 2-4. According to X-ray crystallographic investigations that were carried out on 2 and 4, the oxidation state has a considerable influence on the structure of the Fe2As2Se2 core: significant shortening of the Fe-Fe distance (deltad(Fe-Fe)> 0.3 A) and weakening of the As-As bond length ((deltad(As-As) > 0.3 A) suggests the formal presence of two diatomic AsSe ligands and a Fe-Fe bond. DFT and EHMO calculations confirm that an electron is removed from an occupied Fe-Fe orbital of antibonding character during oxidation. All molecular orbitals lower their energies upon oxidation, but the energy drop is relatively small for those involving the As-As bond. An additional structural feature in 4 consists of an electronic interaction of the iodide with both As atoms which suggests a formally neutral ion pair. Electrochemical studies confirm that the oxidation of 1 is a reversible one-electron process with E(1/2)= +0.07 V (in THF). These studies also reveal that 4 dissociates in polar solvents, such as THF, into [1]+ and I-, which is followed by transformation into 1 and I3.

Mechanism of photoinduced changes in the structure and optical properties of amorphous As2S3.

We propose a mechanism of photostructural changes in amorphous As2S3 ( a-As2S3) on the basis of ab initio molecular orbital calculations on clusters of atoms modeling the local structure of the amorphous system. We have found that trigonal AsS3 pyramidal units can be transformed into a fivefold coordinated As site having four As-S bonds and one As-As bond via a photoionization process. This photoinduced coordination defect center exhibits a lower photoabsorption energy as compared with the usual pyramidal structure, explaining the observed photodarkening effect of a-As2S3.

In-plane structure of an arsenic-adsorbed Si(001) surface probed with grazing-angle x-ray standing waves

The grazing-angle x-ray standing-wave technique has been employed for in-plane structure determination of an arsenic-deposited Si(001) surface with $1\ifmmode\times\else\texttimes\fi{}2$ and $2\ifmmode\times\else\texttimes\fi{}1$ domains. Experimental data were collected using the (220), $(2\ifmmode\bar\else\textasciimacron\fi{}20),$ and (040) Bragg planes nearly perpendicular to the surface under UHV conditions. Three arsenic-emission profiles were fit by calculations based on the x-ray dynamical theory for perfect crystals. The data analysis allows us to limit the possible ranges of an As-As dimer bond length L, an in-plane root mean-square thermal vibrational amplitude $\sqrt{〈{u}_{\ensuremath{\parallel}}^{2}〉},$ and the two domain fractions, ${M}_{1}$ and ${M}_{2}.$ The ranges of the structural parameters, such as L and $\sqrt{〈{u}_{\ensuremath{\parallel}}^{2}〉},$ are consistent with other works. In particular, L and a two-domain area ratio ${M}_{2}{/M}_{1}$ are restricted within the narrow ranges from 2.57 to 2.52 \AA{}, and from 1.35 to 1.29, respectively. Assuming domains are perfectly ordered, it is found that $L=2.52\ifmmode\pm\else\textpm\fi{}0.05\AA{},$ $\sqrt{〈{u}_{\ensuremath{\parallel}}^{2}〉}=0.22\ifmmode\pm\else\textpm\fi{}0.07\AA{},$ ${M}_{1}=0.44\ifmmode\pm\else\textpm\fi{}0.07,$ and ${M}_{2}=0.56\ifmmode\pm\else\textpm\fi{}0.07.$