NiAs Research Articles

Mineral assemblages and the genesis of platinum metal mineralization of the Vuruchuayvench intrusion (Kola Peninsula, Russia)

The layered Vuruchuaivench intrusion is located in the eastern part of the Baltic Shield and is part of the Early Paleoproterozoic Monchegorsk Intrusive Complex. The platinum-metal mineralization of IW is localized within the stratiform platinum-bearing horizon of the reef type with a length of about 2 km and a thickness of 1-3 m, in some boreholes up to 15–20 m. The dissemination of Fe-Cu-Ni sulfides containing the platinum-group minerals, silver and gold is confined to areas of gabbronorites and anorthosites of massive and taxitic texture, with a wide development of fluid-bearing minerals in the intercumulus of cumulative phases. The uniform distribution of petrogenic, rare and rare earth elements in the rocks of the platinum-metal reef (PGE-reef) and its host rocks indicates the formation of gabbronorites during intra-chamber differentiation without additional portions of the melt. The composition and ratios of platinum group minerals (PGMs) with sulfides and silicates suggest a close genetic relationship between PGMs and igneous sulfides. As the temperature decreases, primary PGMs and sulfides are modified under the influence of high-temperature magmatic fluids and hydrothermal solutions, with the formation of a wide range of PGMs. The ores are dominated by palladium arsenides, stibioarsenides, and bismuth tellurides. A special role in the formation of platinum-metal mineralization in the Vuruchuaivench intrusion is played by the separation of an immiscible arsenide melt with the formation of numerous drop-shaped, globular intergrowths predominated by Pd-Ni-arsenides and Pd-stibioarsenides. In some sulfide scattered impregnations, instead of globules consisting of palladium and nickel arsenides, platinum diarsenide (sperrylite) occurs. The formation of specific platinum-metal associations is apparently due to the addition of As, Sb, and other incompatible elements to the magma during extensive assimilation of Archean crustal rocks.

First findings of platinum group minerals from ultramafites of the Idzhim mafic-ultramafic massif (Western Sayan)

In plastically deformed harzburgite and dunite of the Idzhim mafic-ultramafic massif, which is part of the Kurtushiba ophiolite belt of the Western Sayan and is one of largest massifs of this belt, platinum group minerals (PGM) were identified for the first time. They were found in pentlandite, awaruite and nickel arsenides (NiS, Ni2S) in form of finely dispersed inclusions, the diagnosis of which, due to their small size, was carried out only qualitatively. Native osmium, Ir-bearing osmium, native ruthenium, garutiite, tetraferroplatinum, unnamed (Pt,Ir)Fe and (Ni,Cu,Pd,Pt)2-3Fe phases, zaccarinite, Ir-bearing erlikmanite and unnamed sulfides with crystal chemical formula Me2S were quantitatively identified and characterized. All PGM grains found are predominantly localized either in peripheral parts of grains of sulfides, awaruite and wairauite, or in silicate matrix in immediate vicinity of these minerals. The platinum group elements (PGE) content and their distribution in restite ultramafic rocks was apparently controlled by partial melting of primary peridotite substrate. During partial melting, the extraction of sulfur and Pt-group platinoides (Pt, Pd, Rh) into the silicate melt led to a decrease in S2 fugacity and the accumulation of Ir-group platinoides (Os, Ir, Ru) in monosulfide solid solution (mss), from which subsequently primary Os-Ir-bearing pentlandite crystallized. The subsequent transformation of this sulfide led to appearance of PGE-containing awaruite and nickel arsenides, as well as to everything discovered diversity of identified PGM.

Tutorial on Describing, Classifying, and Visualizing Common Crystal Structures in Nanoscale Materials Systems.

Crystal structures underpin many aspects of nanoscience and technology, from the arrangements of atoms in nanoscale materials to the ways in which nanoscale materials form and grow to the structures formed when nanoscale materials interact with each other and assemble. The impacts of crystal structures and their relationships to one another in nanoscale materials systems are vast. This Tutorial provides nanoscience researchers with highlights of many crystal structures that are commonly observed in nanoscale materials systems, as well as an overview of the tools and concepts that help to derive, describe, visualize, and rationalize key structural features. The scope of materials focuses on the elements and their compounds that are most frequently encountered as nanoscale materials, including both close-packed and nonclose-packed structures. Examples include three-dimensionally and two-dimensionally bonded compounds related to the rocksalt, nickel arsenide, fluorite, zincblende, wurtzite, cesium chloride, and perovskite structures, as well as layered perovskites, intergrowth compounds, MXenes, transition metal dichalcogenides, and other layered materials. Ordered versus disordered structures, high entropy materials, and instructive examples of more complex structures, including copper sulfides, are also discussed to demonstrate how structural visualization tools can be applied. The overall emphasis of this Tutorial is on the ways in which complex structures are derived from simpler building blocks, as well as the similarities and interrelationships among certain classes of structures that, at first glance, may be interpreted as being very different. Identifying and appreciating these structural relationships is useful to nanoscience researchers, as it allows them to deconstruct complex structures into simpler components, which is important for designing, understanding, and using nanoscale materials.

A novel optimal formula of nickel extraction: arsenic removal from niccolite by controlling arsenic-containing phases.

Objective: Niccolite, a rare nickel arsenide mineral, has emerged as a promising source for nickel extraction. However, its processing is limited and often associated with toxicity concerns. This study aims to search for efficient separation of arsenic during the roasting process of niccolite. Methods: The arsenic-containing phase was optimized through changing the contents of oxygen, additive S, and additive FeS in the system to achieve efficient separation of arsenic during the roasting process of niccolite. Thermodynamic analysis was performed using the equilibrium composition module with HSC Chemistry. Results: The thermodynamic results showed that in direct roasting, the product contained ferric arsenate which immobilized arsenic in the solid phase, increasing the difficulty in separation. In the presence of sulfur, the arsenic may escape completely in the form of gas (As2O3, As4O4, As4O6). The use of FeS as the reductant significantly reduced the residual arsenic content. Conclusion: The FeS reduction in roasting process is an optimal strategy for arsenic removal from niccolite. This provides a novel technique for nickel extraction in industry.

Physical properties of different polymorphs of sulfur doped ZnO studied in the framework of first-principles approaches

Various physical properties of pure and sulfur-doped zinc oxide in the germanium phosphide (GeP), cesium chloride (CsCl), and nickel arsenide (NiAs) type structures are studied using the first-principles approaches in this research. The structural characteristics of the ZnOS alloys in GeP, CsCl, and NiAs type polymorphs show a slight deviation from Vegard's law, which is consistent with the available literature. It is observed that the electronic band structures of the ZnOS alloys show an exciting impact of sulfur (S) substitution in the ZnO. The ZnOS alloys, in CsCl type structure, display their metallic character. The static dielectric constants of the GeP, CsCl, and NiAs type’s polymorphs demonstrate that with increasing S concentration, polarization is enhanced. Moreover, the CsCl type phase of the ZnOS alloys exhibits the maximum value of the static dielectric constant along with showing metallic character. The optical results highlight the potential of S-doped ZnO in these structures as the highest absorption, reflectivity, and conductivity peaks shift towards low photon energies. The examination of the absorption spectra demonstrates that GeP-type ZnOS alloys are suitable for infrared to visible regime applications. On the other hand, NiAs-type ZnOS alloys are appropriate for use in the visible light regime.

Vacancy‐Ordered Superstructure‐Induced Delocalized States Enable Superior Sodium Ion Storage

AbstractTransition metal sulfides (TMSs) are perceived as competitive candidate anodes for sodium‐ion batteries (SIBs) on account of their high capacity and admirable reversibility. However, a majority of TMSs suffer from huge volume expansion and poor kinetics so they cannot achieve durable and fast Na+ storage. Herein, a cation vacancy‐ordered Cr2/3S is fabricated by extracting quantitative Cr atoms from nickel arsenide type CrS via sulfur “atomic pump,” that is, sulfur and particular sit Cr atoms are bonded to extend a new structure. The ordered vacancies not only construct a loosely‐packed crystal structure but also induce delocalized electron states of Cr atoms, hence effectively accelerating Na+ diffusion and releasing volume strain to enable high‐rate and longevous SIBs. The new Cr2/3S anode presents a high reversible capacity of 544 mAh g−1 after 100 cycles at 1 A g−1 and excellent high‐rate performance of ≈100% capacity retention after 7000 cycles at 20 A g−1. Subsequent in situ and ex situ characterizations reveal the Na+ storage mechanism of Cr2/3S. The proposed cation exaction strategy through an innovative sulfur “atomic pump” can be an efficient way to achieve loosely‐packed structure material for large‐capacity and fast‐kinetics anodes.

Investigations of thermoelectric properties of different gallium nitride polytypes through first-principles approach

In recent years, exploring new polytypes of III-V semiconductors has been widely practiced for the development of thermoelectric devices of high efficiency. In this work, the thermoelectric properties of new polytypes, namely the wurtzite(wz), Berrylium oxide (β-BeO), Nickel arsenide (NiAs), Silicon carbide (SiC), and Titanium arsenide (TiAs) phases of GaN have been investigated using the first-principles approaches. It is found that the p-type of doping induces enhancement of the power factors (PFs) and figure-of-merits (zT) of the GaN polytypes. The optimal p-type doping for PFs has been recognized as −1.67 eV for wz-GaN, −1.78 eV for β-BeO-GaN, −1.33 eV for NiAs-GaN, −1.58 eV for SiC-GaN, and −1.48 eV for TiAs-GaN. These optimal p-type doping has induced the room-temperature PFs as high as 13.75 × 1010 W/mK2s recorded for wz-GaN, 13.61 × 1010 W/mK2s for β-BeO-GaN, 41.14 × 1010 W/mK2s for NiAs-GaN, 14.06 × 1010 W/mK2s for SiC-GaN, and 49.21 × 1010 W/mK2s for TiAs-GaN. Furthermore, the PFs of the GaN polytypes are enhanced by increasing the temperature. Due to such significant PFs, the zT values corresponding to p-type doping have been recorded as 1.013 for wz-GaN, 0.998 for β-BeO-GaN, 1.00 for NiAs-GaN, 1.015 for SiC-GaN, and 0.999 for TiAs-GaN. Moreover, we comprehensively discussed the electrical and thermal conductivities and Seebeck coefficients (S) for the predicted GaN polytypes. The results of the thermoelectric properties presented in this study reveal the predicted GaN polytypes may find interesting applications in thermoelectric devices for clean energy harvesting.

Insight into the structural, electronic, optical, and elastic properties of niobium carbide

ABSTRACT The structural parameters, electronic, optical, and elastic properties of Niobium Carbide (NbC) compound within four different structures: rock-salt (RS), wurtzite (WZ), cesium chloride (CsCl), and Nickel Arsenide (NiAs) are examined using the Full-Potential Linearized-Augmented Plane Wave (FP-LAPW). The exchange–correlation potential (VXC) has been treated by Perdew, Burke, and Ernzerhof's generalized gradient approximation (PBE-GGA) when structural properties, transition pressure, and elastic properties are estimated. For electronic properties, in addition to (PBE-GGA), the modified Becke–Johnson (mBJ-GGA) was used for increased accuracy. Present results show that the RS of NbC is the most stable among the four examined structures with the lowest equilibrium energy. The calculated lattice constants are in good agreement with the former calculations. The elasticity and the formation energy calculations show that NbC is stable within the four studied structures. The electronic band structure calculations of NbC show that it has a metallic nature in the four considered structures.

Petrogenesis of arsenic and platinum-group minerals from a partially serpentinized dunite in East Dover, Vermont, USA

In the Appalachian Mountains of Vermont, USA, variably serpentinized ultramafic rocks mark the Ordovician Taconic orogenic suture zone. These ultramafic rocks provide evidence for several alteration events that occurred during Appalachian orogenesis. The largest of these ultramafic bodies occurs as a partially serpentinized meta-dunite located in East Dover, Vermont. Whole-rock X-ray fluorescence spectroscopy and electron microprobe data on variably serpentinized meta-dunite samples are interpreted with respect to several processes including fluid/melt-rock interaction in the mantle, serpentinization, and subsequent regional metamorphism. We report the first discovery of nickel arsenide minerals hosted in this meta-dunite, as well as rare occurrences of platinum-group mineral inclusions in chromitite. Although the platinum-group minerals and chromitite are rare, their occurrence and chemistry suggest that they formed by fluid/melt-rock interaction during partial melting events that produced the dunite, likely in a supra-subduction zone setting. Arsenic minerals are rare in un-serpentinized samples but are ubiquitous in highly serpentinized samples, which suggests that most of the arsenic was introduced into the ultramafic rocks during serpentinization. Whole-rock geochemical analyses also indicate that highly serpentinized samples contain the highest concentrations of arsenic. The discovery of arsenic minerals identifies a potential source to explain elevated arsenic in groundwater in Vermont, which is a serious health concern in places where wells have been drilled in serpentinite bedrock.

Jahn–Teller Disproportionation Induced Exfoliation of Unit‐Cell Scale ϵ‐MnO2

AbstractExfoliation of non‐layered (structurally) bulk materials at the nanoscale is challenging because of the strong chemical bonds in the lattice, as opposed to the weak van der Waals (vdW) interactions in layered materials. We propose a top‐down method to exfoliate ϵ‐MnO2 nanosheets in a family of charge‐ordered La1−xAExMnO3 (AE=Ca, Sr, Ba) perovskites, taking advantage of the Jahn–Teller disproportionation effect of Mn3+ and bond‐strength differences. ϵ‐MnO2 crystallized into a nickel arsenide (NiAs) structure, with a thickness of 0.91 nm, displays thermal metastability and superior water oxidation activity compared to other manganese oxides. The exfoliation mechanism involves a synergistic proton‐induced Mn3+ disproportionation and structural reconstruction. The synthetic method could also be potentially extended to the exfoliation of other two‐dimensional nanosheet materials with non‐layered structures.

Jahn-Teller Disproportionation Induced Exfoliation of Unit-Cell Scale ϵ-MnO2.

Exfoliation of non-layered (structurally) bulk materials at the nanoscale is challenging because of the strong chemical bonds in the lattice, as opposed to the weak van der Waals (vdW) interactions in layered materials. We propose a top-down method to exfoliate ϵ-MnO2 nanosheets in a family of charge-ordered La1-x AEx MnO3 (AE=Ca, Sr, Ba) perovskites, taking advantage of the Jahn-Teller disproportionation effect of Mn3+ and bond-strength differences. ϵ-MnO2 crystallized into a nickel arsenide (NiAs) structure, with a thickness of 0.91 nm, displays thermal metastability and superior water oxidation activity compared to other manganese oxides. The exfoliation mechanism involves a synergistic proton-induced Mn3+ disproportionation and structural reconstruction. The synthetic method could also be potentially extended to the exfoliation of other two-dimensional nanosheet materials with non-layered structures.

Menshikovite Pd3Ni2As3 and Associating Minerals of Sulfide Ores at the Eastern Flank of the Oktyabrsky Deposit (Norilsk Ore Field)

Considerable amounts of menshikovite (the rare palladium–nickel arsenide Pd3Ni2As3) have been found at the eastern flank of the Oktyabrsky deposit (Norilsk ore field) near the contact of solid and impregnation sulfide Co–Ni–Cu ores within the magnetite–plagioclase–fassaite skarns. The sulfide material of the ores consists of aggregates of chalcopyrite, pentlandite, pyrrhotite, and cubanite produced by subsolidus transformations of high-temperature Iss3, Iss4 and subordinate Mss solid solutions, with ingrowth of later Se‑galena. Menshikovite associated to mertieite II, Ag-gold (756–706 fineness), Au-electrum (694–672 fineness), kotulskite, moncheite, rare altaite, hessite, naldrettite, and melonite consists of fine (30 μm or less) metasomatic ingrowths at the contact of silicate mass and aggregates of sulfides. The composition of menshikovite is close to the theoretical data: (Pd2.98Ru0.03)3.01(Ni1.89Fe0.08Co0.01)1.98 (As2.94Se0.04Bi0.02Sn0.01)3.01. Sperrylite metacrystals truncate the borders of menshikovite accretions along with other minerals of noble metals and contain their “corroded” inclusions. This association of pneumatolytic minerals of noble metals was formed under increased activity of As, Te, Sb, and Bi in fluids with low Sn activity. Menshikovite is characteristic for the Pd-richest Oktyabrsky deposit. Another palladium–nickel arsenide, that is, mayakite PdNiAs, is of quite wide occurrence in the Talnakh and Norilsk 1 deposits. The distribution of Pd and Ni arsenides is probably an element of the mineral zonality of the Norilsk ore field.

Menshikovite Pd<sub>3</sub>Ni<sub>2</sub>As<sub>3</sub> and associated minerals of sulphide ores within the Eastern flank of the Oktyabrsky deposit (Norilsk ore field)

Significant amount of menshikovite (rare palladium and nickel arsenide) Pd3Ni2As3was found on the Eastern flank of the Oktyabrsky deposit (Norilsk ore field), near the contact of solid and impregnation sulfide Co-Ni-Cu ores among magnetite-plagioclase-fassaite skarns. Sulfide material of both ores consists of chalcopyrite, pentlandite, pyrrhotite and cubanite aggregates, which are the products of subsolidus transformations of high-temperature solid solutions Iss3, Iss4 and subordinate Mss; with interpositions of later Se-galenite. Menshikovite in association with mertieite-II, silver-gold (fineness 756–706), golden-electrum (fineness 694–672), kotulskite, moncheite, rare altaite, hessite, naldrettite and melonite forms small (up to 30 microns) metasomatic growths on the contact of silicate matrix and magmatogenic sulfide aggregates. The average composition of menshikovite is close to theoretical data: (Pd2,98Ru0,03)3,01(Ni1,89Fe0,-08Co0,01)1,98(As2,94Se0,04Bi0,02Sn0,01)3,01. Sperrylite metacrystals cut the borders of menshikovite accretions as well as other minerals of precious metals and contain “corroded” inclusions. This association of minerals of noble metals has arisen under the increased activity of As, Te, Sb, Bi and low activity of Sn in fluids. Menshikovite is typical for Pd-rich ores of the Oktyabrsky Deposit, while mayakite PdNiAs (another palladium and nickel arsenide) is relatively widely developed in ores of the Talnakh Deposit (Mayak mine and partly Komsomolsky mine) and the Norilsk-I. Perhaps, such a distribution of palladium-nickel arsenides is an element of mineral zonality of the Norilsk ore field.

Prediction and mapping of landslide hazard in North Sumatera

Mapping of landslide hazard in North Sumatera is very important to identify the areas potential. In this study we try to predict and mapping of landslide hazard in North Sumatera using scoring and GIS. Compare to the ground movement vulnerability and rainfall series, the areas with steep topography have landslide hazard forecasts, which are dominated by zones with medium hazard forecasts. High-level landslide hazard forecast maps are in the areas of South Tapanuli, Mandailing Natal, Humbang Hasundutan, Central Tapanuli, North Tapanuli, South Nias, West Nias, Padang Lawas, Toba Samosir, Langkat, Samosir, Pakpak Bharat, and Karo districts.

Evaluation of rammelsbergite (NiAs2) as a novel mineral for 187Re-187Os dating and implications for unconformity-related U deposits

Rammelsbergite (NiAs2) is often present in ore deposits worldwide in association with other arsenides, sulphides and sulfarsenides. This work demonstrates the value of the application of the Re-Os isotopic system to the dating of rammelsbergite. Using the example of the Cigar Lake uranium deposit (Athabasca Basin, Saskatchewan, Canada), our results show that rammelsbergite concentrates significant and variable amounts of Re when crystallizing, up to 1.6 µg g−1, while incorporating minimal common Os. Such characteristics make this mineral an ideal target for Re-Os isotopic dating, by both isochron and model age methods. Remarkable agreement of the Re-Os age of the rammelsbergite with the U-Pb age of the uranium oxide grains found inside one of the massive rammelsbergite veins confirms the applicability of the method. The selected rammelsbergite samples from the Cigar Lake uranium deposit yield a 187Re-187Os isochron age of 1239 +33/−20 Ma. These results challenge a long-standing petrogenetic model which postulates contemporaneous U oxide and Ni-Co-arsenide deposition in unconformity-related uranium deposits. The new Re-Os age of rammelsbergite veins indicates that arsenide crystallization postdated the deposition of the primary uranium oxides at 1461–1341 Ma, implying that uranium oxides and nickel arsenides, as well as other sulphides and sulfarsenides, were not precipitated contemporaneously during a single hydrothermal event as previously proposed. The 187Re-187Os data suggest that crystallization of rammelsbergite and co-genetic sulphides, arsenides and sulfarsenides was linked to the ca. 1270 Ma Mackenzie magmatic event, marked by the emplacement of mafic dikes throughout the Canadian Shield, including in the area of the Athabasca Basin. This study therefore suggests a new hypothesis for the origin of nickel, cobalt, sulfur and arsenic in unconformity-related U deposits of the Athabasca Basin. More broadly, the successful application of the 187Re-187Os rammelsbergite chronometer in this geological context suggests that its application in other ore deposit environments worldwide is likely to provide similar insights. In this respect, the 187Re-187Os chronometer applied to rammelsbergite, and potentially to other arsenides and sulfarsenides, represents a valuable complement to molybdenite dating because it can be used in systems that lack molybdenite.

Investigations of novel polymorphs of ZnO for optoelectronic applications

Being a promising candidate in next-generation optoelectronic applications, the study of new polymorphs of zinc oxide (ZnO) is receiving the great attention of researchers. In this article, we explore optoelectronic properties of seven polymorphs of ZnO such as wurtzite type, sphalerite type, germanium phosphide (GeP) type, 5-5 type, nickel arsenide (NiAs) type, β-beryllium oxide (BeO) type and cesium chloride (CsCl) type by using full-potential linearized augmented plane wave plus local orbital (FP-L(APW+lo)) method within Density Functional Theory (DFT). Tran-Blaha modified Becke-Johnson potential (TB-mBJ) along with Generalized Gradient Approximation (GGA) proposed by Perdew-Burke-Ernzerhof (PBE) as exchange-correlation has been used for the calculations of electronic and optical properties of seven polymorphs of ZnO. Our band structure calculations reveal the considered polymorphs of ZnO as wide bandgap semiconductors. The calculated band gap values of wurtzite type, sphalerite type, GeP type, 5-5 type, NiAs type, BeO type and CsCl type polymorphs of ZnO are 2.901 eV, 2.679 eV, 2.648 eV, 3.127 eV, 2.986 eV, 3.040 eV and 1.853 eV respectively. The wurtzite type, sphalerite type, 5-5 type, NiAs type, and BeO type polymorphs of ZnO exhibit direct bandgap while GeP type and CsCl type polymorphs show indirect bandgap. The optical spectra of these polymorphs of ZnO reveal different reflection, plasmon energies, optical absorption, and refractive indices are considerably anisotropic and present different values in the x- and z-direction. The z-component of the reflectivity and absorption spectra was found larger than the x-component in wurtzite type, 5-5 type and NiAs type polymorphs of ZnO, showing that large reflectivity and optical absorption along z-axis than the x-axis in these polymorphs. This study is believed to provide an interesting guideline for the low-cost and non-toxic new polymorphs of ZnO in cutting-edge optoelectronic applications.

Templated Growth of Metastable Polymorphs on Amorphous Substrates with Seed Layers

Metastable inorganic materials with unique properties are important in many practical applications, but their synthesis is often challenging. In physics, epitaxial stabilization, also known as pseudomorphic growth, is used to synthesize metastable polymorphs, but usually only as very thin films and on expensive single-crystal substrates. In chemistry, the templated growth of inorganic solid-state materials on self-assembled monolayers of organic molecules is reported. Bridging these two fields, here, we show that the synthesis of metastable polymorphs is possible up to large film thickness on amorphous substrates covered with thin inorganic seed layers that serve as templates. The stabilization of a 500-nm-thick metastable wurtzite (WZ) $\mathrm{Mn}\mathrm{Te}$ film by a 5-nm-thick $\mathrm{Zn}\mathrm{Te}$ seed layer sputtered on amorphous glass substrates is experimentally demonstrated. Theoretical calculations explain this experimental observation by the small WZ polymorph energy relative to that of the ground-state nickeline (NC) structure of $\mathrm{Mn}\mathrm{Te}$ and a large lattice constant difference of the two. The resulting metastable WZ-$\mathrm{Mn}\mathrm{Te}$ polymorph exhibits a wide band gap of 2.7 eV and a low hole density of ${10}^{12}\phantom{\rule{0.25em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$, which is relevant to optoelectronic applications. These properties are in sharp contrast to those of the narrow-band-gap highly doped NC-$\mathrm{Mn}\mathrm{Te}$ with 1.3 eV band gap and ${10}^{19}\phantom{\rule{0.25em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$ hole density. The difference in hole density is due to the calculated difference in the formation energy of manganese vacancy acceptor defects. Overall, these results suggest that templated growth on amorphous substrates with seed layers can be used to synthesize metastable polymorphs of other materials, without the need for expensive single-crystal substrates.

First-Principles Study of Divalent 3d Transition-Metal Carbodiimides.

Using first-principles density-functional theory calculations, an in-depth study on the divalent 3d transition-metal carbodiimides with the general formula MNCN (M = Cr-Cu) is performed. Experimentally, two different types of crystal structures are adopted for these, namely the (Jahn-Teller distorted) nickel arsenide [NiAs] and the rock salt [NaCl] type, and their occurrence from the formation energy and chemical bonding is rationalized. As already suspected many years ago, on the basis of empirical tight-binding arguments, the intrinsic mechanism for the preferred crystal structure lies in the metal-metal overlap population, reflected from crystal orbital Hamilton population (COHP) analysis data. Not too surprisingly, there is an increase in covalency for the metal-N bonds in MNCN upon increasing the atomic number of the metal, well-mirrored in the COHP, Mulliken charge transfer, and also charge-density analysis.

Non-listed Nias Exposure Assessment: Comparison of Different Tools

Food contact materials (FCMs) can contain Non-intentionally added substances (NIAS) as a result of break down, side product or impurities. NIAS can migrate into food and this might cause a risk for human health. Thus, their presence has to be evaluated, but currently there are no protocols to establish how to perform a risk assessment. Then, in this work, three different strategies to make a NIAS exposure assessment were compared: the European Food Agency Authority (EFSA) food consumption database, the Matrix Tool and the FACET tool. 2,4-Di-tert-butylphenol (2,4-DTB), an identified and quantified NIAS, was used as the case study. Differences between these tools were highlighted, but for all the strategies tested the estimated exposure to 2,4-DTB was lower than its threshold value indicating that there are no risk for the consumers.

A Revision of the Genus Phaedis Pascoe (Coleoptera: Tenebrionidae: Stenochiinae) from Sumatra Including Nias and Mentawai Islands

The genus Phaedis of Sumatra is revised. Thirteen known species are recognised from the island and adjacent islands, in which eleven known species are redescribed or noted with additional description; eighteen new species are described under the following names, and a key to the species of Sumatra is given: P. coeruleovirenssp. nov., P. convexussp. nov., P. eleganssp. nov., P. kanieisp. nov., P. kraatzisp. nov., P. merklisp. nov., P. nanussp. nov., P. notaticollissp. nov., P. notatipennissp. nov., P. obscuripennissp. nov., P. obtusidenssp. nov., P. pubigasterussp. nov., P. purpureostriatussp. nov., P. rubripessp. nov., P. schultheissisp. nov., P. signatussp. nov., P. kaszabisp. nov., and P. yokoiisp. nov. A new species group, Shibatai species group, is proposed.