Interstitial Positions Research Articles

Light-Induced Defect Healing and Strong Many-Body Interactions in Formamidinium Lead Bromide Perovskite Nanocrystals.

Organic lead halide perovskite (OLHP) nanocrystals (NCs) have paved the way to advanced optoelectronic devices through their extraordinary electrical and optical properties. However, understanding of the light-induced complex dynamic phenomena in OLHP NCs remains a subject of debate. Here we used wide field microscopy and time-resolved spectroscopy to correlate the local changes in photophysics and the dynamical behavior of photocarriers. We demonstrate that light-induced brightening of the photoluminescence from the formamidinium lead bromide NC films is related to the film preparation condition and reduction of trap density. The density of trap states is reduced via halide ion migration from interstitial position. Our femtosecond transient absorption study identifies transient Stark effect due to the generation of hot carriers. Because of slow carrier trapping, Auger recombination through many-body carrier-carrier interactions dominates over trion recombination. This work presents unprecedented insights into the light-driven processes enabling better device design in the future.

Visible light-induced degradation of antibiotic ciprofloxacin over Fe–N–TiO2 mesoporous photocatalyst with anatase/rutile/brookite nanocrystal mixture

Titanium dioxide photocatalysts co-modified with iron and nitrogen (Fe–N–TiO2) were produced via hydrothermal method using iron(III) nitrate nonahydrate and urea as iron and nitrogen sources, respectively. The effects of different dopant concentrations were investigated. The modified TiO2 catalysts were characterized for phase composition, surface morphology, specific surface area, degree of doping, charge states and bandgap energy combining various techniques. The results showed that controlled iron and nitrogen concentrations significantly altered the physicochemical properties of the catalysts. The photocatalysts displayed the anatase/rutile/brookite crystal phase mixture. The rutile and brookite phase contents increased with increasing iron content. On the other hand, increasing nitrogen content inhibited the formation of rutile and brookite phases and the catalysts displayed predominantly the anatase phase. High iron and low nitrogen contents led to the highest BET surface areas. The surface morphology changed from nanorice to spherical shape with increasing iron content. The bandgap energy of all Fe–N–TiO2 samples was in the range 2.7–3.1 eV, being lower than that of undoped TiO2 and pure anatase phase. Nitrogen was incorporated into the TiO2 lattice on interstitial positions (Ti–O–N). The iron, substituting some Ti4+ in the lattice was presented in Fe2+ and Fe3+ oxidation state, as confirmed by XANES measurements. The photocatalytic degradation of antibiotic ciprofloxacin was performed under visible light using a LED illumination source and nearly 70 % of the antibiotic was removed in 6 h by using the most active sample (2.5 %N–1.5 %Fe). As verified by photoluminescence results, the iron and nitrogen dopants synergistically enhanced the charge separation, since they promoted the formation of the different TiO2 phases.

First-principles study of the insertion and diffusion of interstitial atoms (H, C, N and O) in nickel

Solubility and diffusivity of interstitials in Ni is of prime importance to understand and quantify reactivity of Ni-base structural alloys at high temperature. We thus present a first-principles study of the insertion and diffusivity of interstitial species in nickel. We put an emphasis on carbon, nitrogen and oxygen atoms and compare our results with those found for hydrogen and in the literature. The interactions with the metal and the relative stability of sites are discussed in detail in terms of phonon, electronic, elastic, magnetic properties and charge transfers. As a result, we identified one new stable interstitial position for C and N atoms, and we also showed that the tetrahedral site can be considered as unstable from an elastic standpoint for carbon. In the light of these new results, diffusion mechanisms were reviewed and diffusion coefficients were calculated. The effects of temperature on enthalpy and migration energies were investigated. We thus showed that C and N atoms on one hand, H and O atoms on the other hand, show the same behavior.

Geochemical features of soils in an undulating glaciolacustrine sandy plain in the middle taiga subzone of Karelia

The geochemically conjugate series of soils (Albic Podzol – Albic Podzol Gleyc – Hystosol) formed on an undulating glaciolacustrine plain in the middle taiga of Karelia was investigated. Surveys for redox conditions showed them to vary from oxidizing in automorphic soils to reducing in soils occupying accumulation-favoring locations. The geochemical coefficients descriptive of the features of accumulation and directions of migration in the studied soils were calculated and analyzed. The distribution of silicic acid and a majority of sesquioxides inside the profile of the studied soils is typical of podzols. The podzolic horizons of the soils occupying interstitial positions have a faster outmigration of elements than in automorphic soils, while their Al-Fe-humic horizons accumulate aluminum, iron, titanium and phosphorus. All the soils are deficient in a majority of microelements as compared to their background levels; very low concentrations were determined for nickel, cobalt and manganese. The content of copper and sometimes zinc is at the background level. The distribution of the studied elements across the soil profile follows the accumulation-eluviation-illuviation pattern, but the scope of variation in the migration of elements varies among topographic positions. In well-drained locations microelements are quite monotonously distributed through the lower part of the soil profile, while soils in transitional landscapes have a higher differentiation of microelements. The differentiation of the catena through lateral migration is of the transient eluviation type, i.e. soils in lower-lying positions are poorer in the studied elements than soils in automorphic positions. This pattern is due to the natural characteristics of the area: low surface slope, homogeneous sandy parent material, low humus content in soil.

Investigation of interaction between <i>α</i>-Fe metal and H atom by ab-initio method

Hydrogen-induced cracking (HIC) is a key problem restricting the application of ultra-high strength steel. It is necessary to analyze the distribution of diffusible hydrogen to reveal the mechanism of HIC. The site occupation tendency of H in interstitial and vacancy positions are investigated by the ab-initio method, and the stable configuration and steady state energy are obtained. The solution tendency of H atom in interstitial and vacancy positions is analyzed based on the aforementioned results. Specifically, the Mulliken population, density of states, charge density difference are calculated and used to analyze the interaction between <i>α</i>-Fe metal and H atom. The results show that the dissolved H tends to occupy the interstitial sites of the body-centered cubic, the weak hybridization interaction between the interstitial hydrogen and its nearest neighbour Fe atom is contributed by the H 1s orbital and Fe 4s orbital. Vacancies can capture H atoms easily and H atoms tend to occupy the isoelectric surface near the inwall of the vacancies. A vacancy defect can hold up to three H atoms which are difficult to combine with each other to form H<sub>2</sub> molecule by covalent bond. H atoms in vacancies and at interstitial positions change the charge distribution of the Fe lattice, which weakens the binding force of the atoms and forms anti-bonding orbital in local area. The proposed thermodynamical model allows the determining of the equilibrium vacancy and the dissolved H concentration for a given temperature and H chemical potential in the reservoir, and the calculated results are in good agreement with the actual results.

Musical Fusion as Contextualized Boundary-Play: Samba Jazz in New York City

Musical Fusion as Contextualized Boundary-PlaySamba Jazz in New York City Marc M. Gidal (bio) Music scholars regularly address "fusion" and "boundaries" together because fusion implies combinations of musical elements and practices whose distinctions help define categorical boundaries, musical or extra-musical. To explain jazz-rock-funk fusion during the 1970s, for example, Kevin Fellezs defined his topic accordingly: "For my purposes fusion will refer to a merging of jazz, rock, and funk music aesthetics and practices and the subsequent (or, better, the further) blurring of these large-scale genre boundaries in articulation with other musical traditions […]"1 Deborah Pacini Hernandez addressed intersections of hybridity, identity, and boundary-work to study "innovative blends" in US "Latino popular music": Despite—and sometimes because of—their interstitial position within the United States' racial imaginary, Latinos' personal and collective hybrid genealogies have served to facilitate the bridging and crossing of musical borders. Indeed, Latinos have generated an extraordinary variety of innovative blends of Latin American, African American, and Euro- American aesthetics, bringing into dialogue with each other in multiple overlapping and intersecting ways.2 To expand this approach, we could frame creative acts of musical fusion and discourses about them through the lens of the sociological concept "symbolic boundary-work," in the sense that they express and bridge differences, symbolic and social.3 Boundary-awareness can happen during boundary-crossing activities that may produce fusions, as well as boundary-maintenance that may favor authenticity. When listeners notice musical combinations that challenge their categorical expectations such as an album that, as Jennifer Lena explains, "is not obviously located within one or another position in the classification system, sociologists will refer to it as a boundary object."4 The dismissive quip that fusing jazz with other genres amounts to "confusion"—asserted by, for example, "jazz purists" about jazz-rock fusions and Indian classical "traditionalists" about Indian-jazz fusions—illustrates judgments about boundary-crossing as well [End Page 52] as the subjectivity of evaluation.5 To juxtapose the terms "musical fusion" and "boundary-work" might, at first glance, seem to combine opposite intentions: the former implies mixture and the latter separation. However, sociologists have explained that studies of symbolic boundary-work examine degrees of flexibility, types of interactions, and effects under the umbrellas of "boundary properties (i.e. permeability, salience, durability, and visibility) as well as mechanisms 'associated with the activation, maintenance, transposition or the dispute, bridging, crossing and dissolution of boundaries.'"6 As I summarized elsewhere, sociological studies of boundary-work through music often correlate musical tastes of listeners/consumers with social stratification, expanding upon Pierre Bourdieu's Distinction; and, by contrast, ethnomusicologists have drawn on symbolic boundary-studies when relating music-making practices with issues of social-group identity.7 To adjust sociological terms for music studies, the "work" in boundary-work might be stated in creative-artistic terms as practice, process, performance, or play. To this end, I suggest that boundary-play suits the variety of boundary- conscious "fusing activities" that musicians use and that audiences, critics, and scholars interpret.8 I use "play" in a broad sense to embrace playing music, creative play, and social play in relation to identity, culture, and society. In short, musical fusion features playful mediations of symbolic and social boundaries. Depending on the context, musicians, listeners, and scholars apply their understandings of categorical similarities and differences when recognizing musical practices that seem borrowed and combined, and when interpreting musical meaning in boundary-play. In this article I explore four interrelated points through a case study of samba jazz, a type of Brazilian-jazz fusion, as played and interpreted in New York City, with comparisons to interpretations of Brazilian jazz in Brazil. My first point is that musical fusion can be explained as symbolic boundary-work, which I am calling boundary-play for its creative-artistic implications. Second, boundary- play can encompass a wide range of musical interactions between and within categories (traditions, genres, styles, etc.), and relates to musicians' multiple competencies, affinities, and identities. Third, the different contexts of musical fusions can influence interpretations of boundary-play even if descriptions of musical fusions may be the same or similar. Specifically, interpretations of Brazilian jazz in Brazil...

In Search of the Global East: Thinking between North and South

Carving up the world into Global North and Global South has become an established way of thinking about global difference since the end of the Cold War. This binary, however, erases what this paper calls the Global East — those countries and societies that occupy an interstitial position between North and South. This paper problematizes the geopolitics of knowledge that has resulted in the exclusion of the Global East, not just from the Global North and South, but from notions of globality in general. It argues that we need to adopt a strategic essentialism to recover the Global East for scholarship. To that end, it traces the global relations of IKEA’s bevelled drinking glass to demonstrate the urgency of rethinking the Global East at the heart of global connections, rather than separate from them. Thinking of such a Global East as a liminal space complicates the notions of North and South towards more inclusive but also more uncertain theorizing.

Effect of Hydrogen Electrosorption on Mechanical and Electronic Properties of Pd80Rh20 Alloy.

The interaction of hydrogen with Pt-group metals and alloys is at the center of research in the fields of electrochemistry, electrocatalysis, hydrogen technologies and fuel cells developed under the Hydrogen Economy. In this work, the material under study was Pd80Rh20 alloy (50 μm foil) subjected to hydrogen electrosorption at potentials corresponding to formation of α, α-β and β phase in 0.1 M H2SO4 at 25 °C. The total amount of hydrogen adsorbed at the surface and absorbed in octahedral interstitial positions of fcc Pd80Rh20 alloy, was determined from the oxidation charges. The H/(Pd+Rh) was 0.002, 0.4 and 0.8 for α, α-β, and β Pd80Rh20H, respectively. Microindentation hardness testing and nanoindentation showed weakening of mechanical properties of the Pd80Rh20 alloy after hydrogen electrosorption due to internal stresses. Decrease of work function with increasing amount of hydrogen absorbed occurred due to the surface roughness changes and the presence of electropositive hydrogen atoms absorbed in the crystal lattice responsible for the dipole interaction. The detailed mechanism of hydrogen absorption/diffusion in the Pd80Rh20 alloy structure is discussed. The obtained results give a new insight into the relationship between the amount of absorbed hydrogen and mechanical and electronic properties of the Pd80Rh20 alloy at the micro- and nanoscale.

First-principle study of the solubility and diffusion of oxygen and boron in [formula omitted]-TiAl

Solubility and diffusion of boron and oxygen in the γ-TiAl intermetallic compound are herein investigated by first-principle calculations. On the basis of the space group of the γ phase, the accommodation of the light atoms in the various interstitial positions is studied by density functional theory. Diffusion coefficients are also obtained from ab initio calculations. Barrier energies for the boron and oxygen diffusion among the different stable interstitial sites are computed using the Nudged Elastic Band method and atomic jumping rates are obtained from the Transitional State Theory. Diffusion coefficients are obtained from the solution of the transport equation in the infinite time limit, using the analytical Multi-State Diffusion method. The methodology here applied is validated by the good agreement between the computed diffusion coefficient of boron and the experimental data available in the literature for this species.

Loss of ADAMTS19 causes progressive non-syndromic heart valve disease.

Valvular heart disease is observed in approximately 2% of the general population1. Although the initial observation is often localized (for example, to the aortic or mitral valve), disease manifestations are regularly observed in the other valves and patients frequently require surgery. Despite the high frequency of heart valve disease, only a handful of genes have so far been identified as the monogenic causes of disease2-7. Here we identify two consanguineous families, each with two affected family members presenting with progressive heart valve disease early in life. Whole-exome sequencing revealed homozygous, truncating nonsense alleles in ADAMTS19 in all four affected individuals. Homozygous knockout mice for Adamts19 show aortic valve dysfunction, recapitulating aspects of the human phenotype. Expression analysis using a lacZ reporter and single-cell RNA sequencing highlight Adamts19 as a novel marker for valvular interstitial cells; inference of gene regulatory networks in valvular interstitial cells positions Adamts19 in a highly discriminatory network driven by the transcription factor lymphoid enhancer-binding factor 1 downstream of the Wnt signaling pathway. Upregulation of endocardial Krüppel-like factor 2 in Adamts19 knockout mice precedes hemodynamic perturbation, showing that a tight balance in the Wnt-Adamts19-Klf2 axis is required for proper valve maturation and maintenance.

Właściwości wybranych materiałów o składzie niestechiometrycznym stosowanych na powłoki przeciwzużyciowe

The article analyzes the influence of fill ratio of interstitial positions by nitrogen or carbon on technological and functional properties of transient metals of groups from IVb to VIb. In addition to literature data, the results of own comparative studies on the durability of cutting edges coated with transition metal nitrides with stoichiometric and non-stoichiometric composition are presented.

New Family of Argyrodite Thioantimonate Lithium Superionic Conductors.

We report on a new family of argyrodite lithium superionic conductors, as solid solutions Li6+xMxSb1-xS5I (M = Si, Ge, Sn), that exhibit superionic conductivity. These represent the first antimony argyrodites to date. Exploration of the series using a combination of single crystal X-ray and synchrotron/neutron powder diffraction, combined with impedance spectroscopy, reveals that an optimal degree of substitution (x), and substituent induces slight S2-/I- anion site disorder-but more importantly drives Li+ cation site disorder. The additional, delocalized Li-ion density is located in new high energy lattice sites that provide intermediate interstitial positions (local minima) for Li+ diffusion and activate concerted ion migration, leading to a low activation energy of 0.25 eV. Excellent room temperature ionic conductivity of 14.8 mS·cm-1 is exhibited for cold-pressed pellets-up to 24 mS·cm-1 for sintered pellets-among the highest values reported to date. This enables all-solid-state battery prototypes that exhibit promising properties. Furthermore, even at -78 °C, suitable bulk ionic conductivity of the electrolyte is retained (0.25 mS·cm-1). Selected thioantimonate iodides demonstrate good compatibility with Li metal, sustaining over 1000 h of Li stripping/plating at current densities up to 0.6 mA·cm-2. The significantly enhanced Li ion conduction and lowered activation energy barrier with increasing site disorder reveals an important strategy toward the development of superionic conductors.

Identification of ribosomal sites and karyotype analysis in Festuca ulochaeta Steud. and Festuca fimbriata Ness., grasses native to Brazil.

Festuca L. has more than 600 perennial species described, which makes it the largest genus within the family Poaceae. In Brazil, only two native species of Festuca have been described, for which cytogenetic studies need to be strengthened: Festuca ulochaeta and Festuca fimbriata. The aim of this study was to characterize the karyotypes of F. ulochaeta and F. fimbriata based on the mapping of rDNA sites. The FISH was performed with 35S and 5S rDNA probes. Both species have 42 chromosomes, of which 36 were metacentric and six were submetacentric. Festuca fimbriata has two pairs of 35S rDNA sites, one located on the metacentric pair 4, in an interstitial position, and one at the submetacentric pair 14 in the proximal position. Festuca ulochaeta has one pair of 35S rDNA in interstitial-proximal position in the metacentric pair 3. Both species showed 5S rDNA sites only on chromosome pair 21 in the terminal position of the short arm. The analysis of the chromosomal characteristics indicates that these species have a symmetrical karyotype and allopolyploid origin.

Swamps of hydrogen in equiatomic FeCuCrMnMo alloys: First-principles calculations

High-entropy alloys (HEAs) merit promising applications in nuclear reactors. A FeCuCrMnMo HEA with low activation under neutron irradiation was studied, which was first focused on the search of an equilibrium state by a hybrid method combining the Metropolis Monte Carlo method and density functional theory (DFT). As a transmutation byproduct in fission reactions or fuel for fusion reactions, the evolution of hydrogen, in the HEA was then investigated through a systematic analysis of H solution and diffusion using DFT and molecular dynamics simulations. Rooted in the unique distortion of HEA lattices, i.e., the destroyed translational symmetry of the energy landscape, tetrahedral and octahedral interstitial positions have no significant difference in the priority of H residing. Diffusion of H, as a guest atom, also presents a sluggish effect. The dramatic increases and decreases in potential energy generate a great number of insurmountable barriers pervading the matrix and largely suppressing the mobility of H. However, this effect originates not only from the difference between the potential energies of interstitial positions as observed with host atoms, which increases the fluctuation of migration barriers and decreases the effective atomic jump frequency, but also from the destabilization of interstitial positions for H residing. This blocks the diffusion channels of H and further decreases the atomic jump probability in Einstein's equation. The present investigation provides fundamental insight into H behavior in HEAs and clues for the application of HEAs as materials of tritium permeation barriers or resistance to hydrogen irradiation.

NaM2(PO4)(SO4)2 (M= Fe, V, Cr) As Electroactive Materials for Na-Ion Batteries

To date, research on sodium-ion batteries started to gain more interest. It is mainly motivated by the large abundance of sodium and the hope to produce batteries that are cheaper compared to LIBs and less prone to resource issues and safety concerns [1-3]. NASICON compounds have been well investigated as possible electroactive materials for sodium-, lithium-, and magnesium-ion batteries. In this paper, we report on the structural and electrochemical properties of the NASICON phases NaFe2-xMx(PO4)(SO4)2 (M=V, Cr and 0 < x < 1) [4] . The crystal structures were solved by the Rietveld method using powder X-ray diffraction (PXRD) data. The electrochemical performances were examined by galvanometric cycling and cyclic voltammetry. The stability of the NASICON structure during cycling was also followed by ex-situ PXRD experiments. The NaFe2-xMx(PO4)(SO4)2 powders (0 < x < 1) were synthesized via a solid state synthesis route from stoichiometric mixtures of NaNO3 (Aldrich, ≥99 %), Fe(NO₃)₃·9H₂O (Aldrich, ≥98%), Cr(NO₃)₃·9H₂O (Aldrich, ≥98%), NH4VO₃ (Aldrich, ≥99%), (NH4)2SO4 (Aldrich, ≥99 %), NH4H2PO4 (Merk, ≥99%) and citric acid C6H8O7 (Riedel-deHaën) (CA). The starting raw materials, dissolved in an aqueous medium, were stirred at 80oC until evaporation of water. The resulting powders were calcined at 500oC for several hours under argon to obtain pure NaFe2-xVx(PO4)(SO4)2 powders. TGA experiments performed on all the samples resulted in a 30% weight loss which corresponds to the departure of two SO2 molecules, and hence confirm the chemical compositions of NaFe2-xVx(PO4)(SO4)2. This was also confirmed by EDS analyses. The crystal structure of the NaFe2-xVx(PO4)(SO4)2 were solved using X-ray powder diffraction data. A phase transition from R-3c (x = 0) to R-3 (x > 0) was observed during the replacement of iron by vanadium. The structure can be described as a covalent skeleton [(Fe/V)2P3O12]- built of Fe/VO6 octahedra and XO4 tetrahedra (X= S, P), which forms 3D interconnected channels with several types of interstitial positions where sodium and vacancies are distributed. The cycling performances of NaFe2-xVx(PO4)(SO4)2 were studied in cells embedding (NaPF6:EC:PC) electrolyte and Na-metal (Figure 1). Additional details will be provided during the conference. Figure 1. Charge/discharge curves of NaFe2-xVx(PO4)(SO4)2 at the rate of C/10 vs. Na+/Na (a) and capacity retention for x = 0.4 (b) and rate capability for x = 0.4 (c). Reference: [1] Makino, K.; Katayama, Y.; Miura, T.; Kishi, T., J. Power Sources 2002, 112, 85−89. [2] Gaubicher, J.; Wurm, C.; Goward, G.; Masquelier, C., Nazar, L., Chem. Mater. 2000, 12, 3240−3242. [3] Jian, Z.; Zhao, L.; Pan, H.; Hu, Y.-S.; Li, H.; Chen, W., Chen, L., Electrochem. Commun. 2012, 14, 86−89. [4] H. Ben Yahia, R. Essehli, R. Amin, K. Boulahya, T. Okumura, I. Belharouak, Journal of Power Sources 382 (2018) 144-151. Figure 1

A Comprehensive Profile of Chemokine Gene Expression in the Tissues of the Female Reproductive Tract in Mice

ABSTRACTHomeostatic leukocyte trafficking into and within the female reproductive tract (FRT) contributes to fertility and reproductive health. It is unclear how this process is regulated in the anatomically distinct reproductive tissues, or whether the genes involved are affected by cyclical changes in reproductive hormones. In tissues such as skin and intestine, mouse studies have defined evolutionarily conserved molecular mechanisms for tissue-specific homing, interstitial positioning, and leukocyte egress. Chemokine family members are invariably involved, with the chemokine expression profile of a tissue regulating leukocyte content. Reproductive tissues (ovary, vagina, cervix, uterine horn) of 8 week old virgin female C57BL/6 mice (n = 20) were collected, and expression of mRNA for leukocyte markers and chemokines conducted by qPCR. Lymphocytic and myeloid cell populations within the uterus, cervix, bone marrow and PALN from virgin C57BL/6 mice were determined by flow cytometric analysis. Variation in leukocyte content between reproductive tissues is evident, with the uterus and cervix containing complex mixtures of lymphocytes and myeloid cells. Twenty-six chemokine genes are expressed in the FRT, many by several component tissues, some preferentially by one. Most striking are Xcl1 and Ccl28, which are restricted to the uterus. Ccl20 and genes encoding CXCR2 ligands are primarily transcribed in cervix and vagina. Ovary shows the lowest expression of most chemokine genes, with the notable exception of Ccl21 and Ccl27. We also identify eight chemokines in the vagina whose expression fluctuates substantially across the oestrous cycle. These data reveal complex chemokine networks within the FRT, and provide a framework for future studies of homeostatic leukocyte trafficking into and within these tissues.Abbreviations: BM: bone marrow; DC: dendritic cell; DN: double negative; FRT: female reproductive tract; FSC: forward scatter; NK: natural killer; PALN: para-aortic lymph node; SSC: side scatter; Tregs: regulatory T cells

First-principle investigation of electronic structures and interactions of foreign interstitial atoms (C, N, B, O) and intrinsic point defects in body- and face-centered cubic iron lattice: A comparative analysis

Carbon, Nitrogen, Boron and Oxygen are common alloying elements in ferritic as well as in austenitic steels and their small concentration of only few parts per million significantly influence the materials mechanical properties. In this report, a detailed comparative analyses of electronic structures and interactions of foreign solute atoms (C, N, B, and O) with point defects (vacancy/interstitial) in bcc- and fcc-iron lattices as obtained from density functional theory calculations are presented. It is found that the energetically favourable configurational site for B atom is the substitutional site in bcc-Fe whereas it is the octahedral interstitial site in fcc-Fe. For all other solute (C, N, O) atoms octahedral interstitial position is energetically favourable in both Fe lattices. The stability of all solute atoms is discussed from view point of their chemical nature as well as geometrical factor. In addition, the interaction of B atom with the point defects in the two Fe-lattices is found to be quite different as compared to any other solute atoms. We found that B atom strongly binds the point defects in bcc-Fe, in contrast, repels in fcc-Fe lattice. Furthermore, strong resemblance is observed between B atom and vacancy regarding their nature of interaction with other point defects in bcc-Fe lattice. Although vacancy always exhibit strong attraction with solute atoms in both Fe-lattices, the trapping ability of the vacancy in bcc-Fe is found to be stronger than that in fcc-Fe. The interaction among V-SAm cluster is also calculated for m upto 5 in order to investigate the trapping ability of a vacancy and covalent bond formation is observed in case of C atoms only in bcc-Fe lattice. Further insights into electronic structure and interaction of the point defects in the two Fe lattices have been obtained from density of states and differential charge density calculations.

Synthesis and characterization of the nanostructured solid solution with extended solubility of graphite in nickel by mechanical alloying

In the present work, mechanical alloying of a powder mixture of nickel and graphite (up to 15wt%) was carried out in an attrition mill under a nitrogen atmosphere. The as-milled powders were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and transmission electron microscopy (TEM). The 15wt% graphite dissolved into the nickel (exceeding the negligible solid solubility in the nickel-carbon system), thereby forming a supersaturated solid solution of graphite in a nickel matrix. The dissolved graphite occupied interstitial positions along the dislocation edges and at the grain-boundary regions. A three-step graphite dissolution mechanism has been proposed. The associated changes in the nickel lattice, such as changes in the crystallite size (62 to 43 nm), lattice strain (0.12% to 0.3%), and lattice parameter (0.3533 to 0.3586 nm), which led to the formation of the supersaturated solid solution, were also evaluated and discussed.

Theoretical study of self-trapped hole diffusion in CaF2, SrF2, BaF2 crystals

In this paper we present the results of ab initio molecular dynamics (MD) study of the Vk-center in CaF2, SrF2, BaF2 crystals. The calculations have been carried using density functional theory in DFT + U approximation. The MD simulation showed three possible diffusion channels of Vk-center: (i) 0°-degree jump, (ii) jump with 90° reorientation, and (iii) jump through an intermediate state in BaF2 and SrF2 crystals. The intermediate state appears when one of the fluorine ions composing Vk-center is displaced into the nearest interstitial position and may be considered as the pair of nearest anion vacancy and H-center. This state cannot be considered as standalone Vk-center configuration but is rather metastable and briefly relaxes into ground state of Vk-center. The existence of this state in SrF2 and BaF2 crystals distinguish them from CaF2 crystal where it has not been observed.

Photocatalytic degradation of flumequine with B/N codoped TiO2 catalyst: Kinetics, main active species, intermediates and pathways

N doped and B/N codoped TiO2 photocatalysts were synthesized by liquid phase precipitation combined with solid phase thermal decomposition method. For comparison, the same method was also used to prepare undoped TiO2 samples. The prepared catalysts were characterized using various techniques including XRD, BET, FT-IR, UV–vis DRS, XPS, SEM and Raman spectroscopy. BET results showed that 300B-N/TiO2 sample has higher BET surface area than undoped TiO2 and N-TiO2 samples. XPS analysis indicated that the B atoms mainly occupy the interstitial position of the TiO2. The photocatalytic performance of prepared undoped and doped TiO2 catalysts was evaluated under simulated sunlight irradiation by employing flumequine (FLU) as a target compound. The photocatalytic performance of TiO2 catalyst can be obviously enhanced by B/N codoping. In addition, B/N codoped TiO2 catalysts exhibit excellent cycling stability. The photocatalytic activity remained 90.1% for 300B-N/TiO2 after four repeated runs. The scavenger study shows that the main reactive species in the photocatalytic degradation process of FLU were superoxide radical (O2−) and photogenerated electrons (e−). Based on detected degradation intermediates of FLU, three possible degradation pathways for FLU were proposed. The degradation of FLU occurs mainly by means of hydroxyl addition and subsequent demethylation and decarboxylation reactions, substitution of fluorine atom by hydroxyl and ring opening of quinolone ring. This work offers a simple method for fabrication of B/N codoped TiO2 photocatalysts, which will be effective in the removal of fluoroquinolones (FQs) in real wastewater.