Chemical Trends Research Articles

Porous carbons: a class of nanomaterials for efficient adsorption-based hydrogen storage

This review provides an overview of porous carbon materials and their hydrogen storage properties with insight on strategic improvement by structural and chemical modifications and current trends of using machine learning and lifecycle assessment.

Elemental abundance differences in the massive planet-hosting wide binary HD 196067−68

ABSTRACT It has been suggested that small chemical anomalies observed in planet-hosting wide binary systems could be due to planet signatures, where the role of the planetary mass is still unknown. We search for a possible planet signature by analysing the TC trends in the remarkable binary system HD 196067–HD 196068. At the moment, only HD 196067 is known to host a planet that is near the brown dwarf regime. We take advantage of the strong physical similarity between both stars, which is crucial to achieving the highest possible precision in stellar parameters and elemental chemical abundances. This system gives us a unique opportunity to explore whether a possible depletion of refractories in a binary system could be inhibited by the presence of a massive planet. We performed a line-by-line chemical differential study, employing the non-solar-scaled opacities, in order to reach the highest precision in the calculations. After differentially comparing both stars, HD 196067 displays a clear deficiency in refractory elements in the TC plane, a lower iron content (0.051 dex), and also a lower Li i content (0.14 dex) than its companion. In addition, the differential abundances reveal a TC trend. These targets represent the first cases of an abundance difference around a binary system hosting a super-Jupiter. Although we explored several scenarios to explain the chemical anomalies, none of them can be entirely ruled out. Additional monitoring of the system as well as studies of larger sample of wide binary systems hosting massive planets are needed to better understand the chemical abundance trend observed in HD 196067−68.

Ion Mobility in Crystalline Battery Materials

AbstractIon mobility in electrolytes and electrodes is an important performance parameter in electrochemical devices, particularly in batteries. In this review, the authors concentrate on the charge carrier mobility in crystalline battery materials where the diffusion basically corresponds to hopping processes between lattice sites. However, in spite of the seeming simplicity of the migration process in crystalline materials, the factors governing mobility in these materials are still debated. There are well‐accepted factors contributing to the ion mobility such as the size and the charge of the ions, but they are not sufficient to yield a complete picture of ion mobility. In this review, possible factors influencing ion mobility in crystalline battery materials are critically discussed. To gain insights into these factors, chemical trends in batteries, both as far as the charge carriers as well as the host materials are concerned, are discussed. Furthermore, fundamental questions, for example, about the nature of the migrating charge carriers, are also addressed.

Chemical Trends in Sample Preparation for Nucleic Acid Amplification Testing (NAAT): A Review.

Nucleic acid amplification testing facilitates the detection of disease through specific genomic sequences and is attractive for point-of-need testing (PONT); in particular, the early detection of microorganisms can alert early response systems to protect the public and ecosystems from widespread outbreaks of biological threats, including infectious diseases. Prior to nucleic acid amplification and detection, extensive sample preparation techniques are required to free nucleic acids and extract them from the sample matrix. Sample preparation is critical to maximize the sensitivity and reliability of testing. As the enzymatic amplification reactions can be sensitive to inhibitors from the sample, as well as from chemicals used for lysis and extraction, avoiding inhibition is a significant challenge, particularly when minimising liquid handling steps is also desirable for the translation of the assay to a portable format for PONT. The reagents used in sample preparation for nucleic acid testing, covering lysis and NA extraction (binding, washing, and elution), are reviewed with a focus on their suitability for use in PONT.

100 years of anthropogenic impact causes changes in freshwater functional biodiversity

Despite efforts from scientists and regulators, biodiversity is declining at an alarming rate. Unless we find transformative solutions to preserve biodiversity, future generations may not be able to enjoy nature’s services. We have developed a conceptual framework that establishes the links between biodiversity dynamics and abiotic change through time and space using artificial intelligence. Here, we apply this framework to a freshwater ecosystem with a known history of human impact and study 100 years of community-level biodiversity, climate change and chemical pollution trends. We apply explainable network models with multimodal learning to community-level functional biodiversity measured with multilocus metabarcoding, to establish correlations with biocides and climate change records. We observed that the freshwater community assemblage and functionality changed over time without returning to its original state, even if the lake partially recovered in recent times. Insecticides and fungicides, combined with extreme temperature events and precipitation, explained up to 90% of the functional biodiversity changes. The community-level biodiversity approach used here reliably explained freshwater ecosystem shifts. These shifts were not observed when using traditional quality indices (e.g. Trophic Diatom Index). Our study advocates the use of high-throughput systemic approaches on long-term trends over species-focused ecological surveys to identify the environmental factors that cause loss of biodiversity and disrupt ecosystem functions.

100 years of anthropogenic impact causes changes in freshwater functional biodiversity.

Despite efforts from scientists and regulators, biodiversity is declining at an alarming rate. Unless we find transformative solutions to preserve biodiversity, future generations may not be able to enjoy nature's services. We have developed a conceptual framework that establishes the links between biodiversity dynamics and abiotic change through time and space using artificial intelligence. Here, we apply this framework to a freshwater ecosystem with a known history of human impact and study 100 years of community-level biodiversity, climate change and chemical pollution trends. We apply explainable network models with multimodal learning to community-level functional biodiversity measured with multilocus metabarcoding, to establish correlations with biocides and climate change records. We observed that the freshwater community assemblage and functionality changed over time without returning to its original state, even if the lake partially recovered in recent times. Insecticides and fungicides, combined with extreme temperature events and precipitation, explained up to 90% of the functional biodiversity changes. The community-level biodiversity approach used here reliably explained freshwater ecosystem shifts. These shifts were not observed when using traditional quality indices (e.g. Trophic Diatom Index). Our study advocates the use of high-throughput systemic approaches on long-term trends over species-focused ecological surveys to identify the environmental factors that cause loss of biodiversity and disrupt ecosystem functions.

Structural Controls on the Origin and Emplacement of Lithium-Bearing Pegmatites

Abstract Exploration and mining of lithium pegmatites has increased in recent years to meet the growing demand for critical metals, which are required for electric-powered transportation as well as sustainable energy production and storage. Pegmatite deposits produced approximately 60% of global lithium production in 2018, the vast majority of which was from spodumene pegmatites. However, there is lack of comprehensive models linking mineral system evolution and structural controls of lithium pegmatites. The majority of studies on lithium pegmatites have focused on chemical fractionation and assume that pegmatites have evolved from a parental granitic source, yet problems emerge when the connection between the granitic source and the pegmatite bodies is not obvious. This lack of connection has given rise to an alternative model of pegmatite formation, the anatectic model. In the anatectic model, granitic pegmatites form from granitic melts produced by partial melting of a suitable lithology, typically pelitic metasediments, without forming a large granitic body followed by fractional crystallization. Here, we first examine the formation of granitic melts related to anatexis, as well as how regional crustal structures influence chemical composition, crustal migration, and melt accumulation within the crust. We next examine the Wekusko Lake pegmatite field located in Manitoba, Canada, in terms of the probable melt source migration, the relationship between crustal-scale strain-zones and spatial pegmatite emplacement, and the chemical fractionation trend that records the formation of lithium-enriched pegmatites.

Exploring the Ability of Hubble Space Telescope WFC3 G141 to Uncover Trends in Populations of Exoplanet Atmospheres through a Homogeneous Transmission Survey of 70 Gaseous Planets

We present analysis of the atmospheres of 70 gaseous extrasolar planets via transit spectroscopy with Hubble’s Wide Field Camera 3 (WFC3). For over half of these, we statistically detect spectral modulation that our retrievals attribute to molecular species. Among these, we use Bayesian hierarchical modeling to search for chemical trends with bulk parameters. We use the extracted water abundance to infer the atmospheric metallicity and compare it to the planet’s mass. We also run chemical equilibrium retrievals, fitting for the atmospheric metallicity directly. However, although previous studies have found evidence of a mass–metallicity trend, we find no such relation within our data. For the hotter planets within our sample, we find evidence for thermal dissociation of dihydrogen and water via the H− opacity. We suggest that the general lack of trends seen across this population study could be due to (i) the insufficient spectral coverage offered by the Hubble Space Telescope’s WFC3 G141 band, (ii) the lack of a simple trend across the whole population, (iii) the essentially random nature of the target selection for this study, or (iv) a combination of all the above. We set out how we can learn from this vast data set going forward in an attempt to ensure comparative planetology can be undertaken in the future with facilities such as the JWST, Twinkle, and Ariel. We conclude that a wider simultaneous spectral coverage is required as well as a more structured approach to target selection.

Periodic table representation of binary, ternary and higher-order systems of inorganic compounds

We enumerate the chemical elements by using the periodicity of the Mendeleev Periodic Table, where the rows reflect the principal quantum number of the electronic configuration of the elements as isolated atoms. By doing that we assign the Periodic Number (PN) to the elements, which expresses much more clearly the chemical similarity between them along the groups. Moving from the unary to higher-order systems, the PN representation shows in an elegantly simple and holistic manner the periodicity of chemical properties and phase stability.By using the PNs of the constituent elements of binary systems, we construct the phase map in which we identify seven regions where phases are not formed, namely the non-former regions. Except for very few distinct systems that violate the identified non-former regions, the seven forbidden regions represent the phase space where phases are not formed in any composition of the constituent elements, whose PNs fall in the given PN ranges also for higher-order systems. In fact, the PN representation of the binary phases map can be easily extended to any higher-order chemical systems to delimit the regions where to search for possible phases, namely the former regions.The powerful usage of the PN representation is seen in the chemical property trends we report for the equiatomic binary phases, for which we calculate, after fully relaxing the crystal structures, the enthalpy of formation, the cohesive energy, the lattice stability and the bulk modulus by using total energy calculations at Density Functional Theory level.

Different Dynamics of the Chemical Composition of Water in the Baikal Ecosystem (Baikal, Its Tributaries, and the Source of the Angara River)

Abstract —Multidirectional dynamics of changes in the chemical composition of the water of the only runoff of Lake Baikal, the Angara River, has been established. The cyclic-wave change in the interannual chemical composition of the Baikal water has been revealed, which indicates a long-term memory effect in the chemical time series of elements. Positive and negative temperature and chemical trends in the state of the water in the source of the Angara are observed, which are due to climate changes, the confinement of Baikal to the rift zone, and the composition of the enclosing rocks. It is shown that the current concentrations of monitored elements in the Angara source water depend also on their past concentrations but can change dramatically in the case of catastrophic environmental disturbances caused by natural and anthropogenic disasters (fires, drought, floods, earthquakes, etc.). The relationship between the elevated concentrations of uranium in the water and the seismic process in the Baikal area has been traced. The data obtained are based on the long-term (1950–2021) monitoring of the chemical composition of water in the Baikal ecosystem (Baikal, its tributaries, and Angara source).

Coherent Chemical Variation Trends of the 55—25 Ma Magmatic Rocks in SE Tibet: N—S Direction Lithospheric Stretching of Eurasia during Early Stage of India—Eurasia Collision

AbstractThe progressive indentation of India into Eurasia generated an E‐W‐trending orthogonal collision belt and a N‐S‐trending oblique collision belt. Compiling available data reveals that ∼70% of the Cenozoic igneous rocks in eastern and southeastern Tibet are concentrated within an ENE‐trending, ∼550–km long and ∼250–km wide magmatic zone (CMZ) that once separated the orthogonal and oblique collision belts. The Latitude 26°N Line is now its southern boundary. The onset timing of magmatism of the CMZ varies gradually from ∼55 Ma in the westernmost part to ∼27 Ma in the easternmost. Then the magmatism successively occurred and suddenly stopped at ∼25 Ma. The segmented and coherent chemical variation trends found suggest that the CMZ magmatic rocks were formed due to partial melting of the heterogeneous upper mantle and crusts of Eurasia. Subduction of Paleo‐ and Neotethyan oceanic plates generated this compositional and mineralogical heterogeneity. Combined with available geophysical data, the CMZ was diachronously formed in response to asthenosphere upwelling induced by NNW—SSE‐direction lithosphere stretching. The difference in responses of the orthogonal and oblique collision belts to the indentation of the Indian continent has led to this lithosphere stretching.

Testing the limits of the global instability index

The global instability index (GII) is a computationally inexpensive bond valence-based metric originally designed to evaluate the total bond strain in a crystal. Recently, the GII has gained popularity as a feature of data-driven models in materials research. Although prior studies have proven that GII is an effective predictor of structural distortions and decomposition energy when applied to small datasets, the wider use of GII as a global indicator of structural stability has yet to be evaluated. To that end, we compute GII for thousands of compounds in inorganic structure databases and partition compounds by chemical interactions underlying their stability to understand the GII values and their variations. Our results show that the GII captures relative chemical trends, such as electronegativity, even beyond the intended domain of strongly ionic compounds. However, we also find that GII magnitudes vary significantly with factors such as chemistry (cation–anion identities and bond character), geometry (connectivity), data source, and model bias, making GII suitable for comparisons within controlled datasets but unsuitable as an absolute, universal metric for structural feasibility.

Trace element and Sr-Nd-Hf-Pb isotope evidence for a multi-magma chamber system beneath the Deccan Volcanic Province, India

With a size of over 500,000 km2, the Deccan Volcanic Province (DVP) covers a large area of the Indian subcontinent. Stratigraphically continuous lava flows piled up to 3000 m record about five million years of volcanic activity. The peak activity of one million years coincides with the migration of the Indian subcontinent across the Réunion plume. Previous studies inferred an isotopic “common signature” for most DVP basalts that is best explained by a mixture of early Réunion plume-related melts and melts from the depleted upper mantle. Further chemical variability of the DVP sequence was explained by the incorporation of material from the lithospheric mantle and continental crust possibly within a single magma chamber system. Yet, indications for a complex crustal magmatic system have also been brought forward by earlier studies and find recently more support in explaining the magmatic plumbing system of the DVP and Large Igneous Provinces in general.This study presents new major and trace element data, including high-precision concentration measurements of high-field strength elements by isotope dilution and Sr-Nd-Hf-Pb isotope compositions for basaltic samples that cover nearly the complete DVP main section. Based on significant variations in Nb/Th (and Th/Ta) over a wide range of MgO concentrations we identified three distinct magma differentiation trends. The distinct differentiation trends result from three types of parental melts that are best explained by different proportions of lower and upper mantle melts indicated by diluted Réunion plume-like trace element and isotope compositions. During their ascent, these separate melts assimilated variable amounts of metasomatized lithospheric mantle and crustal material. Most likely the assimilation occurred before any major differentiation events, thus fixing the Nb/Th (and Th/Ta) of each group regardless of the degree of differentiation. The chemical trends can also be replicated using a statistical numerical approach, confirming that their geochemical signature truly reflects individual differentiation of three distinct parental melts. Field relations require that lavas related to these three unique differentiation trends erupted contemporaneously. This is in contrast to the idea of a gradually evolving single magma chamber system and the concept of a general chemostratigraphy for the DVP main plateau. Rather, our study reveals fast-changing contributions of different mantle reservoirs and provides new insight into the magma-plumbing systems of Large Igneous Provinces that may be more complex.

High-Throughput Exploration of Half-Heusler Phases for Thermoelectric Applications

As a result of the high-throughput ab initiocalculations, the set of 34 stable and novel half-Heusler phases was revealed. The electronic structure and the elastic, transport, and thermoelectric properties of these systems were carefully investigated, providing some promising candidates for thermoelectric materials. The complementary nature of the research is enhanced by the deformation potential theory applied for the relaxation time of carriers (for power factor, PF) and the Slack formula for the lattice thermal conductivity (for figure of merit, ZT). Moreover, two exchange-correlation parametrizations were used (GGA and MBJGGA), and a complete investigation was provided for both p- and n-type carriers. The distribution of the maximum PF and ZT for optimal doping at 300 K in all systems was disclosed. Some chemical trends in electronic and transport properties were discussed. The results suggest TaFeAs, TaFeSb, VFeAs, and TiRuAs as potentially valuable thermoelectric materials. TaFeAs revealed the highest values of both PF and ZT at 300 K (PFp = 1.67 mW/K2m, ZTp = 0.024, PFn = 2.01 mW/K2m, and ZTp = 0.025). The findings presented in this work encourage further studies on the novel phases, TaFeAs in particular.

Density functional analysis of oxide dipole layer voltage shifts in high κ/metal gate stacks

The mechanism of gate threshold voltage (VT) shifts observed in high κ/metal gate stacks is investigated by a density functional theory. This finds that VT depends on the band alignments and the chemical trends between the component oxide layers, such as HfO2, SrO, La2O3, Al2O3, and SiO2. Based on the electron counting rule, we have built three insulating SiO2/SrO, SiO2/La2O3, and SiO2/Al2O3 interfaces, all of which feature a clean bandgap. Two methods have been adopted to derive the band alignments between these four oxides, which are consistent with each other. The results show staggered, “staircase” band alignments and enable La2O3 and Al2O3 layers to shift the metal electrode Fermi level in opposite directions and to approach the Si conduction band and valence band edge positions, respectively. This analysis updates previous empirical models of this effect based on metal oxide ion densities or electronegativity scales and confirms that the oxide layer scheme is suitable for controlling the effective metal work functions in metal–oxide–semiconductor field-effect transistors.

Quantifying Dynamic Tilting in Halide Perovskites: Chemical Trends and Local Correlations

Quantifying Dynamic Tilting in Halide Perovskites: Chemical Trends and Local Correlations

Machine Learning Across Metal and Carbon Support for the Screening of Efficient Atomic Catalysts Toward CO2 Reduction

AbstractDeveloping efficient atomic catalysts (ACs) for the CO2 reduction reaction (CO2RR) still requires ultrahigh experimental resources and a long research period due to the complicated reaction mechanisms and abundant active sites. Herein, this work presents the energy‐based first principles machine learning (FPML) method for the first time based on over 15 000 datasets to directly predict the reaction trends of the CO2RR. The unique scaling relationship of the hydrogenation steps is revealed in ACs for the CO2RR, which is correlated with the active sites instead ofelectron transfer numbers. Based on machine learning (ML) predictions, this work reports that the standard electrode potential is affected by the pH values, and proposes a zero‐point calibration strategy to realize more accurate predictions of electrocatalysis reactions to supply meaningful references to experiments. The formation of electroactive regions constructed by mixing active sites is revealed, which confirms the neighboring effects for the activation of active sites. In addition, the prediction of C3 intermediates indicates the potential of multicarbon coupling processes on the carbon active sites of graphdiyne. This work supplies an effective method to predict chemical reaction trends of different ACs in the CO2RR by ML, which is expected to accelerate the rational design of novel ACs for broad electrocatalysis.

Effects of tri-n-butyl phosphate (TnBP) on neurobehavior of Caenorhabditis elegans.

As an emerging flame retardant, organic phosphate flame retardants have been extensively used worldwide. The aim of this study is to determine the effects of TnBP on neurobehavior of Caenorhabditis elegans (C. elegans) and its mechanisms. L1 larvae of wild-type nematodes (N2) were exposed to TnBP of 0, 0.1, 1, 10, and 20 mg/L for 72 hours. Then, we observed that the body length and body width were inhibited, the head swings were increased, the pump contractions and chemical trend index were reduced, the production of reactive oxygen species (ROS) was increased, and the expression of mitochondrial oxidative stress related genes (mev-1 and gas-1) and P38 MAPK signal pathway-related genes (pmk-1, sek-1, and nsy-1) was altered. After reporter gene strains BZ555, DA1240, and EG1285 were exposed to TnBP of 0, 0.1, 1, 10, and 20 mg/L for 72 hours, the synthesis of dopamine, glutamate, and Gamma-Amino Butyric Acid (GABA) was increased. In addition, the pmk-1 mutants (KU25) led to the sensitivity of C. elegans to TnBP in terms of head swings. The results showed that TnBP had harmful effects on the neurobehavior of C. elegans, oxidative stress might be one of the mechanisms of its neurotoxicity, and P38 MAPK signal pathway might play an important regulatory role in this process. The results revealed the potential adverse effects of TnBP on the neurobehavior of C. elegans.

Lanthanide-doped MoS2 with enhanced oxygen reduction activity and biperiodic chemical trends

Molybdenum disulfide has broad applications in catalysis, optoelectronics, and solid lubrication, where lanthanide (Ln) doping can be used to tune its physicochemical properties. The reduction of oxygen is an electrochemical process important in determining fuel cell efficiency, or a possible environmental-degradation mechanism for nanodevices and coatings consisting of Ln-doped MoS2. Here, by combining density-functional theory calculations and current-potential polarization curve simulations, we show that the dopant-induced high oxygen reduction activity at Ln-MoS2/water interfaces scales as a biperiodic function of Ln type. A defect-state pairing mechanism, which selectively stabilizes the hydroxyl and hydroperoxyl adsorbates on Ln-MoS2, is proposed for the activity enhancement, and the biperiodic chemical trend in activity is found originating from the similar trends in intraatomic 4f–5d6s orbital hybridization and interatomic Ln–S bonding. A generic orbital-chemistry mechanism is described for explaining the simultaneous biperiodic trends observed in many electronic, thermodynamic, and kinetic properties.

Measurement of the Dzyaloshinskii-Moriya Interaction in Mn4N Films That Host Skyrmions.

Mn4N thin film is one of the potential magnetic mediums for spintronic devices due to its ferrimagnetism with low magnetization, large perpendicular magnetic anisotropy (PMA), thermal stability, and large domain wall velocity. Recent experiments confirmed the existence of tunable magnetic skyrmions in MgO/Mn4N/CuxPt1-x(x = 0, 0.5, 0.9, 0.95), and density functional theory (DFT) calculation provided a large theoretical value of the interfacial Dzyaloshinskii-Moriya interaction (iDMI) of Mn4N/Pt, which is consistent with the predicted chemical trend of the DMI in transition metal/Pt films. So far, the measured DMI has not been reported in Mn4N, which is needed in order to support the predicted large DMI value. This paper reports the average DMI of MgO/Mn4N(17 nm)/CuxPt1-x(3 nm) extracted from the anomalous Hall effect with various tilted angles, which is based on magnetic droplet theory with DMI effects. The DMI decreases from 0.267 mJ/m2 to 0.011 mJ/m2 with non-linear tendencies as Cu concentration in the CuxPt1-x capping layer increases from 0 to 1, demonstrating the control of the DMI through the CuxPt1-x capping layer. Furthermore, a solid solution model is developed based on an X-ray photoelectron spectroscopy (XPS) compositional depth profile to analyze the possible effects on the DMI from the mixing layers at the surface of Mn4N. After taking into account the mixing layers, the large DMI in Mn4N film with Pt capping is consistent with the predicted DMI.