Theoretical Investigation of Muon and Muonium Trapping and Hyperfine Interactions in the Chemical Ferromagnet p-NPNN (β-phase)

The trapping sites for muon and muonium in β-phase ferromagnetic p-NPNN have been determined by the first-principles Unrestricted Hartree–Fock procedure. Four trapping sites are found for the muon near the two nitrogen and two oxygen atoms of the two NO groups. For the singlet state of trapped muonium, two trapping sites are found near the two oxygens of two NO groups and for the triplet state two trapping sites are found near the two oxygens of the NO₂ group. The observed μSR signal at zero field with frequency 2.1 MHz is assigned to the singlet muonium sites near the two oxygens of the two NO groups and the high frequency signal ascribed to an isotropic hyperfine constant of 400 MHz is assigned to the two trapped muon sites near the two nitrogen atoms of the two NO groups. This revised version was published online in September 2006 with corrections to the Cover Date.     

Structures,stabilities and electronic properties of manganese oxyfluoride (MnOxFy) species (x + y = 1–4; x,y = 0–4)

In this work, a density functional survey on manganese oxyfluoride (MnO_xF_y) species for x + y = 1–4 is performed, in which an Mn atom interacts simultaneously with O as well as F atoms. The stabilities of all these species are established against dissociation to manganese oxides as well as fluorides and their relative stabilities are also discussed. It is revealed that the most favourable oxidation state of Mn is +4 in its oxyfluorides, same as in fluorides. For the first time, the superhalogen properties of MnOF₃, MnO₃F and MnO₂F₂ species are introduced on the basis of their high electron affinities as compared to halogens. The interaction of MnO₂F₂ superhalogen with an alkali metal (K) is considered via F atoms as well as O atoms which is similar to that in KF and leads to the formation of stable KMnO₂F₂ complex. Thus, this study is expected to motivate theorist to design a new series of superhalogen species using transition metals with mixed F and O ligands, as well as experimentalists to synthesise such novel complex compounds.     

On the Spin Depolarization of a Hall Ferromagnet in the Vicinity of ν = 1 in Two-Dimensional Electron Systems Based on ZnO

JETP Letters - The behavior of the degree of spin polarization and the specific exchange energy near the Hall ferromagnetic state with filling factor ν = 1 in strongly interacting...     

Structures and energetics of BenGen (n = 1–5) and Be2nGen (n = 1–4) clusters

Cluster geometries and energies of Be_nGe_n (n = 1–5) and Be_2nGe_n (n = 1–4) have been examined in theoretical electronic structure calculations. Structure optimisations were carried out using DFT B3LYP/6-31G(2df) and the energies of the optimum geometries were ordered in QCISD(T) calculations. Be and Ge bond to each other and to other atoms of their own kind, creating a great variety of low-energy clusters in a variety of structural types. Comparisons of the germanide clusters with previously explored silicide and carbide structures reveal some structural similarities, but the germanides have much more in common with the beryllium silicides than with the carbides. However, germanide clusters show a greater tendency to form cage-like structures with potential in technological applications.     

Repulsion of a Néel-Type Skyrmion from a Pearl Vortex in Thin Ferromagnet–Superconductor Heterostructures

JETP Letters - In this paper we study repulsion of a Néel-type skyrmion in a chiral ferromagnetic film from a superconducting Pearl vortex due to the stray fields. Taking into account an...     

Determination of iodide in urine based on chemiluminescence system of cerium (IV)–tween 40–iodide

In acidic medium, the oxidation reaction of cerium (IV) with iodide can produce strong chemiluminescence (CL) in the presence of surfactant tween 40 as an enhancer. On this basis, a flow injection method with CL detection was established for the determination of iodide. The method is simple, rapid and effective to determine iodide in the range of 8.0×10^?8–5.0×10^?5 mol/L with a determination limit of 5.0×10^?8 mol/L. The relative standard deviation is 2.7% for the determination of 5.0×10^?6 mol/L iodide (n=11). The method has been applied to determine the content of iodide in urine with satisfactory results. Furthermore, it is suggested that the light emission from cerium (IV)–tween 40 reaction is probably because of the formation of singlet oxygen ¹O₂^? and the emitter is excited oxygen molecular pairs O₂(¹Δ_g)O₂(¹∑_g^?).     

Magnetic ordering in Fe2−xZnxMoO4(X=0.1–1) spinel

We have studied the diluted Fe_2−xZn_xMoO₄ spinel ferrite which shows a frozen disordered magnetic state at low temperature. Magnetic properties are examined by DC magnetisation measurements as a function of temperature, field and time and AC susceptibility experiment. Our measurements show that this disordered magnetic system at low fields, shares many common features with spin glass or cluster glass like phases. Results suggest that the interaction gradually changes as the magnetic ion concentration decreases by the substitution of non-magnetic Zn on A site and causing a perturbation to the magnetically ordered spins and magnetic order decreases.     

Structure and stability of SiBn+ AND CBn+ (n = 1–4)

The structures and binding energies of small boron-rich clusters are studied using correlated wave functions and polarization basis sets. Carbon is the central atom in CB_n⁺, while SiB_n⁺ prefers planar boron networks with silicon as one of the edge atoms. These ground state structures can be explained by differences in the electronegativities of the component elements. The various fragmentation channels of SiB_n⁺ are also examined using binding energy differences.     

Determination of a Dose Absorbed in a Biological Sample under Mixed Gamma–Neutron Irradiation

Technical Physics - A method is proposed and results on determination of absorbed doses under mixed gamma–neutron irradiation of biological samples on a horizontal channel of the IR-8...     

The properties of ferroelectric compound (S)-(+)-4-(1-methylheptyloxycarbonyl)phenyl 4′-(4-cyanoacetoxybut-1-oxy) biphenyl-4-carboxylate and its ability of an antiferroelectric phase induction in mixtures

Phase transitions and ferroelectric properties of (S)-(+)-4-(1-methylheptyloxycarbonyl)phenyl 4′-(4-cyanoacetoxybut-1-oxy)biphenyl-4-carboxylate will be described in this article. This compound exhibits the synclinic smectic C* phase and it has the ability to induce an antiferroelectric phase in mixtures with the other ferroelectric compounds. New systems with induced antiferroelectric phase and their properties are presented.     

First principles investigation of hydrogen isotope effects in [XSO4–H–SO4X]− (X = H,K) complexes

Hydrogen isotope effects on geometries, total energies, nuclear and electronic wave functions of the [HO₃SO–H–OSO₃H]^? and [KO₃SO–H–OSO₃K]^? complexes are investigated with the NEO/HF method. This method determines both electronic and nuclear wave function simultaneously. A discussion of the isotope effects is provided and used to explain the hydrogen isotope effects on the phase transition temperatures in hydrogen bonded ferroelectric materials, K₃H(SO₄)₂ and K₃D(SO₄)₂.     

Determination of the electron phonon coupling and the superconducting gap in β-(BEDT-TTF)2X crystals (X=I3, IAuI)

We performed point-contact and tunneling measurements on the organic superconductors -(BEDT-TTF)₂I₃ and -(BEDT-TTF)₂IAuI, in the normal and superconducting states. The point-contact measurement in the normal state provides the Eliashberg function ²()F (). This function has maxima at 4 and 15 mV, as well as a sharp peak at 1 mV which seems to indicate a very soft phonon strongly coupled to the electrons. The measurements in the superconducting state provide the superconducting gap, which for the tunneling measurements has a value 2/k_B T_c4, just slightly above the BCS value.     

A systematic investigation of the geometries,electronic and magnetic properties of AlnAsq (q = −1, 0, +1; n = 1–16) clusters: a DFT calculation

The geometries, electronic and magnetic properties of Al_nAs^q (q = ?1, 0, +1; n = 1–16) clusters have been investigated systematically by using an unbiased CALYPSO structure searching method and density functional theory. The lowest energy structures show that the As atom prefers to occupy the peripheral position of Al_n+1 clusters instead of the endohedral position. For cationic and neutral clusters, the structural transition from bilayer-like structure to cage-like structure is observed at cluster size n = 12, while it occurs at n = 13 for anionic clusters. The calculated detachment energies (DEs), ionisation potentials (IPs) and electronic affinities (EAs) are consistent with the available experimental and theoretical results for small clusters, indicating that the calculated lowest energy structures are reliable. Furthermore, the DE, EA and IP values for cluster size n ≥ 6 are successfully predicted. A stability analysis shows that Al₅As and Al₁₂As⁺ clusters have relatively large HOMO–LUMO energy gaps, corresponding to the magic numbers of 20 and 40 valence electrons, respectively.     

Chemical origin of C–O blue shift and nature of Cu+…C bonding in non-classical copper carbonyl Cu+(CO)n (n = 1–8) complexes

Natural bond orbital (NBO) method and atoms-in-molecules (AIM) theory are used to study the chemical origin in the direction and ordering of C–O frequency shift, as well as Cu^+…C bond nature in copper carbonyl cations Cu⁺(CO)_n (n = 1–8). This study emphasises the role of π-back donation in explaining the ordering of C–O blue shift. NBO analyses show that the interplay of two competing factors, including π-back donation and rehybridization, is responsible for both the direction and the ordering of C–O stretching frequency shift in Cu⁺(CO)_n (n = 1–8) complexes. In addition, the Cu^+…C interaction is interesting because Cu⁺(CO)_n (n = 1–4) structure has one-sphere CO ligands but Cu⁺(CO)_n (n = 5–8) has two-sphere CO ligands. Topological analyses of electron density are applied to characterise the Cu^+…C interactions of first- and second-sphere CO with Cu⁺ and to explore the Cu^+…C interactions in the nature.     

Special Features of the Reflection Coefficient in (Pb0.78Sn0.22)1–xInxTe (x = 0.05–0.20)

Spectral dependences of the reflection coefficient R are studied in solid solutions of (Pb_0.78Sn_0.22)_1–x In _x Te with indium content in the mixture x = 0.05–0.20 at T = 300 K. In the R() spectra of each of the examined specimens, two minima of the reflection coefficient are revealed: one in the short-wavelength region at = 1–2 m, and the other – in the long-wavelength region at = 25–30 m, the latter being due to plasma vibrations of free electrons. Peculiar features of the short-wavelength minima in the R() dependences are analyzed. It is shown that these minima are likely to be associated with heterogeneities formed by the nonuniform spatial distribution of indium in the specimen.