Atomic Sphere Research Articles

Regulating Local Coordination Sphere of Ir Single Atoms at the Atomic Interface for Efficient Oxygen Evolution Reaction.

Single-atom catalysts dispersed on an oxide support are essential for overcoming the sluggishness of the oxygen evolution reaction (OER). However, the durability of most metal single-atoms is compromised under harsh OER conditions due to their low coordination (weak metal-support interactions) and excessive disruption of metal-Olattice bonds to enable lattice oxygen participation, leading to metal dissolution and hindering their practical applicability. Herein, we systematically regulate the local coordination of Irsingle-atoms at the atomic level to enhance the performance of the OER by precisely modulating their steric localization on the NiO surface. Compared to conventional Irsingle-atoms adsorbed on NiO surface, the atomic Ir atoms partially embedded within the NiO surface (Iremb-NiO) exhibit a 2-fold increase in Ir-Ni second-shell interaction revealed by X-ray absorption spectroscopy (XAS), suggesting stronger metal-support interactions. Remarkably, Iremb-NiO with tailored coordination sphere exhibits excellent alkaline OER mass activity and long-term durability (degradation rate: ∼1 mV/h), outperforming commercial IrO2 (∼26 mV/h) and conventional Irsingle-atoms on NiO (∼7 mV/h). Comprehensive operando X-ray absorption and Raman spectroscopies, along with pH-dependence activity tests, identified high-valence atomic Ir sites embedded on the NiOOH surface during the OER followed the lattice oxygen mechanism, thereby circumventing the traditional linear scaling relationships. Moreover, the enhanced Ir-Ni second-shell interaction in Iremb-NiO plays a crucial role in imparting structural rigidity to Ir single-atoms, thereby mitigating Ir-dissolution and ensuring superior OER kinetics alongside sustained durability.

Single atomic Fe-dispersed hollow carbon spheres coated with Co3O4 synergistically catalyze oxygen reduction and oxygen evolution reactions

It is highly expected to construct an efficient electrocatalyst having dual active sites that can simultaneously catalyze both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in Zn-air batteries (ZABs). In this study, a new core-shell nanostructure (Co3O4/Fe-N4/HCS) consisting of single atomic Fe (Fe-N4)-dispersed hollow carbon spheres (Fe-N4/HCS) coated with Co3O4 nanoparticles (NPs) were successfully synthesized with SiO2 templates by a coating-polymerization-etching preparation strategy. Benefit from a synergistic effect of Co3O4 and Fe-N4 dual active species with unique HCS structure, Co3O4/Fe-N4/HCS displayed outstanding activity in both ORR (half-wave potential = 0.88 V) and OER (overpotential at 10 mA cm−2 = 0.33 V), respectively. Meanwhile, compared to Co3O4/Fe-N4/C with Co3O4 NPs on Fe-N4/C, Co3O4/Fe-N4/HCS with Co3O4 NPs on Fe-N4/HCS exhibits a higher stability during electrochemical processes depending on the stronger interaction between the Co3O4 NPs and atomic dispersed Fe-N4 sites embedded in unique HCS structure. Particularly, the ZABs fabricated by Co3O4/Fe-N4/HCS demonstrates a higher specific capacity (688.7 mAh gZn−1) and superior cycling durability over 80 h. The presence of the electron transfer from Co3O4 to Fe-N4 in Co3O4/Fe-N4/HCS, enables Fe-N4 bonded carbon electron deficiency. This promotes the deposition of Co3O4 NPs and enhances metal-HCS support interactions, which combined with a protecting effect of hollow carbon spherical shell on Co3O4 NPs inside the shell, achieving excellent catalytic stability. This research introduces a novel approach to design dual active sites as high-performance bifunctional ORR/OER catalysts.

Method for Surface Characterization Using Solid-State Nuclear Magnetic Resonance Spectroscopy Demonstrated on Nanocrystalline ZnO:Al.

Nanoscale zinc-oxide doped with aluminum ZnO:Al is studied by different techniques targeting surface changes induced by the conditions at which ZnO:Al is used as support material in the catalysis of methanol. While it is well established that a variety of 1H and 27Al resonances can be found by solid-state NMR for this material, it was not clear yet which signals are related to species located close to the surface of the material and which to species located in the bulk. To this end, a method is suggested that makes use of a paramagnetically impregnated material to suppress NMR signals close to the particle surface in the blind sphere around the paramagnetic metal atoms. It is shown that it is important to use conditions that guarantee a stable reference system relative to which it can be established whether the coating procedure is conserving the original structure or not. This method, called paramagnetically assisted surface peak assignment, helped to assign the 1H and 27Al NMR peaks to the bulk and the surface layer defined by the blind sphere of the paramagnetic atoms. The assignment results are further corroborated by the results from heteronuclear 27Al{1H} dipolar dephasing experiments, which indicate that the hydrogen atoms are preferentially located in the surface layer and not in the particle core.

Surface-Grafted Single-Atomic Pt-Nx Complex with a Precisely Regulating Coordination Sphere for Efficient Electron Acceptor-Inducing Interfacial Electron Transfer.

Based on the electron-withdrawing effect of the Pt(bpy)Cl2 molecule, a simple post-modification amide reaction was firstly used to graft it onto the surface of NH2-MIL-125, which performed as a highly efficient electron acceptor that induced the conversion of the photoinduced charge migration pathway from internal BDC→TiOx migration to external BDC→PtNx migration, significantly improving the efficiency of photoinduced electron transfer and separation. Furthermore, precisely regulating over the first coordination sphere of Pt single atoms was achieved using further post-modification with additional bipyridine to investigate the effect of Pt-Nx coordination numbers on reaction activity. The as-synthesized NML-PtN2 exhibited superior photocatalytic hydrogen evolution activity of 7.608 mmol g-1 h-1, a remarkable improvement of 225 and 2.26 times compared to pristine NH2-MIL-125 and NML-PtN4, respectively. In addition, the superior apparent quantum yield of 4.01 % (390 nm) and turnover frequency of 190.3 h-1 (0.78 wt % Pt SA; 129 times compared to Pt nanoparticles/NML) revealed the high solar utilization efficiency and hydrogen evolution activity of the material. And macroscopic color changes caused by the transition of carrier migration paths was first observed. It holds profound significance for the design of MOF-Molecule catalysts with efficient charge carrier separation and precise regulation of single-atom coordination sphere.

Surface‐Grafted Single‐Atomic Pt−Nx Complex with a Precisely Regulating Coordination Sphere for Efficient Electron Acceptor‐Inducing Interfacial Electron Transfer

AbstractBased on the electron‐withdrawing effect of the Pt(bpy)Cl2 molecule, a simple post‐modification amide reaction was firstly used to graft it onto the surface of NH2‐MIL‐125, which performed as a highly efficient electron acceptor that induced the conversion of the photoinduced charge migration pathway from internal BDC→TiOx migration to external BDC→PtNx migration, significantly improving the efficiency of photoinduced electron transfer and separation. Furthermore, precisely regulating over the first coordination sphere of Pt single atoms was achieved using further post‐modification with additional bipyridine to investigate the effect of Pt−Nx coordination numbers on reaction activity. The as‐synthesized NML‐PtN2 exhibited superior photocatalytic hydrogen evolution activity of 7.608 mmol g−1 h−1, a remarkable improvement of 225 and 2.26 times compared to pristine NH2‐MIL‐125 and NML‐PtN4, respectively. In addition, the superior apparent quantum yield of 4.01 % (390 nm) and turnover frequency of 190.3 h−1 (0.78 wt % Pt SA; 129 times compared to Pt nanoparticles/NML) revealed the high solar utilization efficiency and hydrogen evolution activity of the material. And macroscopic color changes caused by the transition of carrier migration paths was first observed. It holds profound significance for the design of MOF‐Molecule catalysts with efficient charge carrier separation and precise regulation of single‐atom coordination sphere.

Heteroleptic Ni(II) complexes containing chelating benzoato ligand with sharp bite angle: syntheses, crystal structures, and magnetism

From the system Ni(OH)2 – 4,4′-dmbpy – HBz (HBz = benzoic acid; 4,4′-dmbpy = 4,4′-dimethyl-2,2′-bipyridine) under various experimental conditions three complexes were isolated, namely light blue [Ni(4,4′-dmbpy)(Bz)2(H2O)] (1), violet [Ni(4,4′-dmbpy)2(Bz)](Bz)·2HBz (2), and pink microcrystalline product [Ni(4,4′-dmbpy)3](Bz)2·3.5H2O (3). The crystal structures of 1 and 2 were determined, that of 2 at two temperatures (100 and 277 K). The crystal structure of 1 is formed of neutral molecules, in which the Ni(II) central atom is hexa-coordinated by one chelating diamine ligand, one chelating and one monodentate benzoato ligands, and one aqua ligand. The crystal structure of 2 is ionic and in the complex cation the Ni(II) atom is hexa-coordinated by two chelating diamine ligands and one chelating benzoato ligand. The positive charge of the complex cation is counterbalanced by a benzoate anion, and two additional molecules of benzoic acid are present in the asymmetric unit. Magnetic properties of 1 and 2 were studied in the temperature range 1.8 – 300 K and confirmed strong axial single-ion anisotropy (D/kB = -7.78 K for 1, D/kB = -6.52 K for 2) of the Ni(II) ions in line with the deformed coordination spheres of the central atoms. In addition, antiferromagnetic spin dimers of Ni(II) ions mediated by hydrogen bonds are present in 1 with exchange coupling J/kB = -2.19 K. The obtained experimental results were supported by ab initio and DFT calculations.

Going Beyond the GW Approximation Using the Time-Dependent Hartree-Fock Vertex.

The time-dependent Hartree-Fock (TDHF) vertex of many-body perturbation theory (MBPT) makes it possible to extend TDHF theory to charged excitations. Here we assess its performance by applying it to spherical atoms in their neutral electronic configuration. On a theoretical level, we recast the TDHF vertex as a reducible vertex, highlighting the emergence of a self-energy expansion purely in orders of the bare Coulomb interaction; then, on a numerical level, we present results for polarizabilities, ionization energies (IEs), and photoemission satellites. We confirm the superiority of THDF over simpler methods such as the random phase approximation for the prediction of atomic polarizabilities. We then find that the TDHF vertex reliably provides better IEs than GW and low-order self-energies do in the light-atom, few-electron regime; its performance degrades in heavier, many-electron atoms instead, where an expansion in orders of an unscreened Coulomb interaction becomes less justified. New relevant features are introduced in the satellite spectrum by the TDHF vertex, but the experimental spectra are not fully reproduced due to a missing account of nonlinear effects connected to hole relaxation. We also explore various truncations of the self-energy given by the TDHF vertex, but do not find them to be more convenient than low-order approximations such as GW and second Born (2B), suggesting that vertex corrections should be carried out consistently both in the self-energy and in the polarizability.

Strain dependent electronic structure, phonon and thermoelectric properties of CuLiX (X=S,Te) half Heusler compounds

We report the strain dependent electronic, phonon and thermoelectric properties of Li-based Half-Heusler compounds. A direct bandgap of 1.50 eV (for CuLiS) and 1.03 eV (for CuLiTe) is observed from HSE calculations. CuLiX (X = S,Te) in their conventional structure are mechanically and dynamically stable semiconductors. However, the compression beyond −15 % (for CuLiS) and −10 % (for CuLiTe) destabilizes the crystal structure due to the overlapping of atomic charge spheres. At the same time, expansion above 4 % produces instability in both systems. The maximum value of Seebeck coefficient significantly increases from ∼1500 μ/VK in both alloys ∼2400 μ/VK in CuLiS and ∼2000 μ/VK in CuLiTe after the application of 5 % compressive strain at 300 K. These alloys achieve maximized thermoelectric efficiency via strain engineering, and thus require further experimental research.

Reactions of Cadmium(II) Halides and Di-2-Pyridyl Ketone Oxime: One-Dimensional Coordination Polymers.

The coordination chemistry of 2-pyridyl ketoximes continues to attract the interest of many inorganic chemistry groups around the world for a variety of reasons. Cadmium(II) complexes of such ligands have provided models of solvent extraction of this toxic metal ion from aqueous environments using 2-pyridyl ketoxime extractants. Di-2-pyridyl ketone oxime (dpkoxH) is a unique member of this family of ligands because its substituent on the oxime carbon bears another potential donor site, i.e., a second 2-pyridyl group. The goal of this study was to investigate the reactions of cadmium(II) halides and dpkoxH in order to assess the structural role (if any) of the halogeno ligand and compare the products with their zinc(II) analogs. The synthetic studies provided access to complexes {[CdCl2(dpkoxH)∙2H2O]}n (1∙2H2O), {[CdBr2(dpkoxH)]}n (2) and {[CdI2(dpkoxH)]}n (3) in 50-60% yields. The structures of the complexes were determined by single-crystal X-ray crystallography. The compounds consist of structurally similar 1D zigzag chains, but only 2 and 3 are strictly isomorphous. Neighboring CdII atoms are alternately doubly bridged by halogeno and dpkoxH ligands, the latter adopting the η1:η1:η1:μ (or 2.0111 using Harris notation) coordination mode. A terminal halogeno group completes distorted octahedral coordination at each metal ion, and the coordination sphere of the CdII atoms is {CdII(η1 - X)(μ - X)2(Npyridyl)2(Noxime)} (X = Cl, Br, I). The trans-donor-atom pairs in 1∙2H2O are Clterminal/Noxime and two Clbridging/Npyridyl; on the contrary, these donor-atom pairs are Xterminal/Npyridyl, Xbridging/Noxime, and Xbridging/Npyridyl (X = Br, I). There are intrachain H-bonding interactions in the structures. The packing of the chains in 1∙2H2O is achieved via π-π stacking interactions, while the 3D architecture of the isomorphous 2 and 3 is built via C-H∙∙∙Cg (Cg is the centroid of one pyridyl ring) and π-π overlaps. The molecular structures of 1∙2H2O and 2 are different compared with their [ZnX2(dpkoxH)] (X = Cl, Br) analogs. The polymeric compounds were characterized by IR and Raman spectroscopies in the solid state, and the data were interpreted in terms of the known molecular structures. The solid-state structures of the complexes are not retained in DMSO, as proven via NMR (1H, 13C, and 113Cd NMR) spectroscopy and molar conductivity data. The complexes completely release the coordinated dpkoxH molecule, and the dominant species in solution seem to be [Cd(DMSO)6]2+ in the case of the chloro and bromo complexes and [CdI2(DMSO)4].

Magnetic Anisotropy Tailoring by 5d-Doping in (Fe,Co)5SiB2 Alloys

Band-structure calculations were performed using the spin-polarized relativistic Korringa–Kohn–Rostoker (SPR-KKR) band-structure method, determining intrinsic magnetic properties, such as magnetic moments, magnetocrystalline anisotropy energy (MAE), and Curie temperatures, of Fe5−x−yCoxMySiB2 (M = Re, W) alloys. The general gradient approximation (GGA) for the exchange–correlation potential and the atomic sphere approximation (ASA) were used in the calculations. Previous studies have shown that for Fe5SiB2, the easy magnetization direction is in-plane, but it turns axial for Co-doping in the range 1 < x ≤ 2.5 (y = 0). Furthermore, studies have shown that 5d-doping enhances the MAE by enabling the strong spin–orbit coupling of Fe–3d and M–5d states. The aim of the present theoretical calculations was to find the dependence of the anisotropy constant K1 for combined Co- and M-doping, building a two-dimensional (2D) map of K1 for 0 ≤ x ≤ 2 and 0 ≤ y ≤ 1. Similar theoretical 2D maps for magnetization and Curie temperature vs. Co and M content (M = W and Re) were built, allowing for the selection of alloy compositions with enhanced values of uniaxial anisotropy, magnetization, and Curie temperature. The magnetic properties of the Fe4.1W0.9SiB2 alloy that meet the selection criteria for axial anisotropy K1 > 0.2 meV/f.u., Curie temperature Tc > 800 K determined by the mean-field approach, and magnetization µ0Ms > 1 T are discussed.

Electronic structure and resonant inelastic x-ray scattering in the mixed [formula omitted]-[formula omitted] transition-metal oxides Sr[formula omitted]CuIrO[formula omitted], Sr[formula omitted]CuPtO[formula omitted], and Sr[formula omitted]ZnIrO[formula omitted

We have investigated the electronic and magnetic properties of one-dimensional Sr3CuIrO6, Sr3ZnIrO6, and Sr3CuPtO6 oxides within the density-functional theory (DFT) using the generalized gradient approximation while taking into account strong Coulomb correlations (GGA+U) in the framework of the fully relativistic spin-polarized Dirac linear muffin-tin orbital band-structure method. The strong spin–orbit coupling (SOC) in these oxides splits the t2g-type manifold into a lower jeff = 3/2 quartet and an upper jeff = 1/2 doublet. The jeff = 1/2 band is almost completely given by linear combinations of d5/2 states. The occupied jeff = 3/2 band is dominated by d3/2 states with some weight of d5/2 states. We have investigated theoretically the resonant inelastic x-ray scattering (RIXS) spectra at the Ir and Pt L3 edges in Sr3CuIrO6, Sr3ZnIrO6, and Sr3CuPtO6. The experimentally measured RIXS spectrum of Sr3CuIrO6 possesses a sharp feature below 1.3 eV corresponding to transitions within the Ir t2g levels. The excitation located from 3 eV to 5 eV is due to t2g→eg transitions. The next two high energy structures appear due to d−d transitions between the charge transfer Ir 5dct states and t2g and eg states. The theoretically calculated RIXS spectra of Sr3ZnIrO6 and Sr3CuIrO6 at the Ir L3 edges are very similar due to the similarity of their energy band structures. The RIXS spectrum at the Pt L3 edge of Sr3CuPtO6 significantly differs from the corresponding spectra at the Ir L3 edge of Sr3CuIrO6 and Sr3ZnIrO6. There are not any intra-t2g transitions in Sr3CuPtO6 due to fully occupied t2g states. Besides, there are additional 5dCu→eg transitions, where the 5dCu states are derived from the tails of the Cu 3d states inside the Pt atomic spheres.

Incommensurately Modulated Cu0.9Pb1.2Sb2.9Se6 in the Lillianite Structure Type.

Samples with the nominal composition Cu0.9Pb1.2Sb2.9Se6 mainly contain a phase with incommensurately modulated lillianite-type structure with the respective composition. Single crystal diffraction with synchrotron radiation enabled a detailed refinement using the superspace group Cmcm(α00)00s with lattice parameters a = 4.16537(5), b = 14.0821(2), c = 19.8234(3) Å, and a modulation vector q = 0.6890(2)a* at room temperature. The structure is built up from tilted and distorted NaCl-type slabs that are interconnected by bicapped trigonal prisms, which mainly host Pb atoms, according to a 4L arrangement. Satellites up to the second order reveal positional and occupational modulation that mainly involves a sequence of Sb and Cu atoms and allows the Se substructure to adapt in a way that Sb and Cu feature predominantly octahedral and tetrahedral coordination, respectively. Above 523 K, satellite reflections disappear, and the crystal structure becomes more disordered with average coordination spheres of both Sb and Cu atoms corresponding to distorted octahedra. This phase transition leads to discontinuities in the evolution of lattice parameters and physical properties as functions of temperature. HRTEM investigations corroborate centrosymmetry and highlight atoms that are strongly affected by the modulation. Measurements of transport properties reveal a p-type semiconductor with a thermoelectric figure of merit up to 0.1 at 623 K. In accordance with B factor analysis, a small amount of substitution could increase zT significantly by optimizing the carrier concentration.

Vibrational Spectra of the thioglycolate complexes of Zn(II) and Cd(II), structure and natural bond orbitals

The objective of this research was to characterize the vibrational spectrum of the Zn(II) and Cd(II) thioglycolate complexes, as well as their structures, vibrational analysis and the natural orbitals of bonds, through the infrared spectrum with Fourier transform (FT -IR) and Raman. The thioglycolate complexes of Zn(II) and Cd(II) were synthesized following procedures given by the graphical method, and structural analysis was performed through a theoretical-experimental method using both, the hybrid RHF/MP2:STO-3G and the experimental FT-IR and FT-Raman spectra. Calculations were performed on the optimized structure and harmonic vibrational wavenumbers for both complexes were obtained. Second derivative of the vibrational spectra and deconvolution analysis were also performed. The infrared and Raman spectra show many combination and overtone bands in both cases. Calculated and experimental spectra confirmed the structural hypothesis considering two ATG (thioglycolic acid) with two water molecules in the coordination sphere of the central atoms. The natural bond orbital analysis (NBO) was also carried out to study the Zn(II) and Cd(II) hybridization leading to a pseudo-octahedral geometry for both complexes.

Stages of Anglo-American cooperation in the framework of the first atomic projects

Nuclear weapons, which have largely defined the landscape of international relations since the mid-20th century and have turned conflicts between great powers into proxy wars and local clashes, were first developed through the collective efforts of the United States and Great Britain during World War II. Although the allies eventually completed their work on nuclear weapons together, their contributions were not equal. This was reflected in the dividends received by each side in the end. In addition, the nuclear projects were not initially conducted separately, experiencing periods of growth and decline in cooperation with each other that did not coincide with the overall trend of allied relations. The purpose of the study is to identify and capture the specific stages of Anglo-American cooperation within the framework of the first atomic projects of Great Britain and the United States. US and UK historiography has studied various aspects of both the American Manhattan Project and the British "Tube Alloys", including the role of diplomacy and the influence of allied cooperation on the development of nuclear weapons. Soviet and Russian historiography, despite a significantly smaller volume of works on this topic, also addressed these issues. However, neither Russian nor American and British researchers have established any clear periodization of allied nuclear projects cooperation. The study demonstrates the dynamics of relations between Great Britain and the United States in the atomic sphere, identifies the main contradictions between allies that led to the stagnation and cessation of atomic cooperation, and indicates the causes of the resumption and intensification of such cooperation. The conclusion separates Anglo-American cooperation into seven stages. Each stage is determined and characterized by the comparative level of project development at a particular moment, as well as constantly changing interests of the both sides.

Charge density redistribution with pressure in a zeolite framework

As a result of external compression applied to crystals, ions relax, in addition to shortening the bond lengths, by changing their shape and volume. Modern mineralogy is founded on spherical atoms, i.e., the close packing of spheres, ionic or atomic radii, and Pauling and Goldschmidt rules. More advanced, quantum crystallography has led to detailed quantitative studies of electron density in minerals. Here we innovatively apply it to high-pressure studies up to 4.2 GPa of the mineral hsianghualite. With external pressure, electron density redistributes inside ions and among them. For most ions, their volume decreases; however, for silicon volume increases. With growing pressure, we observed the higher contraction of cations in bonding directions, but a slighter expansion towards nonbonding directions. It is possible to trace the spatial redistribution of the electron density in ions even at the level of hundredths parts of an electron per cubic angstrom. This opens a new perspective to experimentally characterise mineral processes in the Earth’s mantle. The use of diamond anvil cells with quantum crystallography offers more than interatomic distances and elastic properties of minerals. Interactions, energetic features, a branch so far reserved only to the first principle DFT calculations at ultra-high-pressures, become available experimentally.

Structural Features of K2O-SiO2 Melts: Modeling and High-Temperature Experiments

Despite numerous investigations, the thermodynamic properties of potassium silicates remain apparently contradictory. In situ experiments are complicated by the unstable behavior of a K2O–SiO2 melt in the region of compositions with a high potassium oxide content. In this paper, we study the structure of melts by the method of physicochemical modeling, taking into account the results of high-temperature Raman spectroscopy. To do this, the Raman spectra were curve-fitted, taking into account the second coordination sphere of silicon atoms. From the interpretation of the spectra of K2O–SiO2 glasses and melts having a K2O content of up to 55 mol.%, quantitative characteristics of the system were obtained. Since available information on the thermodynamic properties of potassium silicates is known to be contradictory, coordinated thermodynamic characteristics of potassium silicates, some of which were evaluated, were used as input data for modeling. Structural modeling of glasses and melts of the K2O–SiO2 system was carried out across a range of compositions up to 60 mol.% potassium oxide. The database of structural units of melts of the potassium silicate system, updated according to experimental data, will find practical application in chemistry, geochemistry and engineering fields.

Electronic Structure Calculations with the Exact Pseudopotential and Interpolating Wavelet Basis

Electronic structure calculations are mostly carried out with Coulomb potential singularity adapted basis sets such as STO or contracted GTO. With another basis or for heavy elements, the pseudopotentials may appear as a practical alternative. Here, we introduce the exact pseudopotential (EPP) to remove the Coulomb singularity and test it for orbitals of small atoms with the interpolating wavelet basis set. We apply EPP to the Galerkin method with a basis set consisting of Deslauriers–Dubuc scaling functions on the half-infinite real interval. We demonstrate the EPP–Galerkin method by computing the hydrogen atom 1s, 2s, and 2p orbitals and helium atom configurations He1s2, He1s2s1S, and He1s2s3S. We compare the method to the ordinary interpolating wavelet Galerkin method (OIW–Galerkin), handling the singularity at the nucleus by excluding the scaling function located at the origin from the basis. We also compare the performance of our approach to that of finite-difference approach, which is another practical method for spherical atoms. We find the accuracy of the EPP–Galerkin method to be better than both of the above-mentioned methods.

Sulfur doped FeSe: A first-principles study of its electronic and superconducting properties

The self-consistent first-principles calculations, based on density functional theory (DFT) approach and the Green’s-function-based Korringa-Kohn-Rostoker Atomic Sphere Approximation (KKR-ASA) method within coherent potential approximation (CPA), are performed to investigate the electronic and superconducting properties of FeSe1-xSx (x = 0.0, 0.05) alloys. The spin-unpolarized calculations show a significant effect on the electronic structure for the substitution of S in FeSe. The outcome for electronic and superconducting properties have been examined in terms of changes in the density of states, band structure, Fermi surface, bare Sommerfeld constant, Hopfield parameters, and the superconducting transition temperature (Tc) of FeSe and FeSe0.95S0.05 alloys, respectively. All calculated results in terms of Tc compare well with the available experimental data. It hopes that the studied properties of these alloys would give the possibility to understand the new physics of iron-based superconductors experimentally.

Electronic phase transition in the Re3Ge7 endohedral cluster compound

${\mathrm{Re}}_{3}{\mathrm{Ge}}_{7}$ is a unique electronic material showing low-temperature metal--insulator-like phase transition. Furthermore, bulk superconductivity can be induced in ${\mathrm{Re}}_{3}{\mathrm{Ge}}_{7}$ by hole doping. Here, we present transport properties, temperature-dependent high-resolution powder x-ray diffraction study, and electronic structure of ${\mathrm{Re}}_{3}{\mathrm{Ge}}_{7}$ in the vicinity of the electronic phase transition. Electrical resistivity and heat capacity measurements confirm the anomaly at 58.5 K in zero magnetic field. The Seebeck coefficient changes its sign and exhibits a maximum below the transition temperature indicating substantial changes in the electronic structure. Temperature-dependent structural studies confirm the second-order nature of phase transition, where unit cell parameters show abrupt change at the transition temperature. An analysis of interatomic distances indicates that the shrinkage of the unit cell volume is due to the interatomic changes taking place in the second coordination sphere of Re atoms. Electronic structure calculations reveal strong $5d\ensuremath{-}4p$ hybridization of valence orbitals near the Fermi level, which is situated between two deep pseudogaps of the density of states. The transition to the semiconducting state is accompanied by the opening of a band gap at the Fermi level right above the narrow pocket of hybridized states.

Synthesis of Cellular Silica Using Microbubbles as Templates.

In this work, cellular silica was synthesized by using microbubbles as templates, which contain a mixture of argon and silicon tetrafluoride (SiF4). The latter is generated from decomposition of hexafluorosilicic acid (H2SiF6) at ambient conditions. The specific surface area of cellular silica can be as high as 130 m2/g, the size of the cavity is hundreds-of-nanometers, and the thickness of the cavity wall is around 30 nm. The cavity size, apparent packing density, and porosity of cellular silica strongly depend on the nature of the aqueous solutions; the cavity size appears to be negatively proportional to the surface tension, but thickness of cavity walls seems to be weakly affected by the aqueous properties. An attempt was made to introduce aluminum atoms in situ in the second-coordination sphere of Si atoms and/or load aluminum into the silica structure. Cellular silica with large pores facilitate the transfer of large molecules, including polymers and enzymes; thus, it could find applications in (bio)catalysis, sorption, controlled release and separations.