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Controlling the oxidation state of constituents by tuning the oxidizing environment and materials chemistry is vital to the successful synthesis of targeted binary or multicomponent oxides. We have conducted a comprehensive thermodynamic analysis of 137 binary oxides to calculate their Ellingham diagrams. It is found that the “reactive” elements that oxidize easily are the f-block elements (lanthanides and actinides), elements in groups II, III, and IV (alkaline earth, Sc, Y, Ti, Zr, and Hf), and Al and Li. In contrast, the “noble” elements are easily reduced. These are coinage metals (Cu, Ag, and especially Au), Pt-group elements, and Hg and Se. Machine learning-based sequential feature selection indicates that the ease of oxidation can be represented by the electronic structures of pure elements, for example, their d- and s-valence electrons, Mendeleev numbers, and groups, making the Periodic Table a useful tool for qualitatively assessing the ease of oxidation. The other elemental features that weakly correlate with the ease of oxidation are thermochemical properties such as melting points and the standard entropy at 298 K of pure elements. Applying Ellingham diagrams enables the oxidation of multicomponent materials to be predicted, such as the Fe–20Cr–20Ni alloy (in wt. %) and the equimolar high entropy alloy of AlCoCrFeNi. These Ellingham diagram-based predictions are in accordance with thermodynamic calculations using the CALPHAD approach and experimental observations in the literature.

Dislocation core dominates dislocation mobility and mechanical properties of crystalline solids. To date, a complete landscape for describing dislocation with narrow core in metals like aluminum (Al) remains elusive, and thus deformation mechanisms of Al alloys are still unclear. This work investigates the dislocation core structure and deformation behaviors of Al alloyed with solutes X (X = Mg, Si, Cu, Zn, and Fe) within the framework of semi-discrete variational theory combined with first-principles calculations. Depending on the dislocation core characteristics, the deformation modes of Al alloys are governed by the compositional-dependent misfit potentials. Except for Fe, all other solutes in Al decrease the intrinsic SF energy, with considerable effects being Mg and Si. The deformation tends to occur via cross-slip of dislocations in Al alloyed with Mg, whereas Si additions can benefit to deform via emission of partial dislocations. Our investigation offers theoretical guidance for choosing solutes favorable to mechanical performances of Al alloys.

Cross phenomena, representing responses of a system to external stimuli, are ubiquitous from quantum to macro scales. The Onsager theorem is often used to describe them, stating that the coefficient matrix of cross phenomena connecting the driving forces and the fluxes of internal processes is symmetric. Here we show that this matrix is intrinsically diagonal when the driving forces are chosen from the gradients of potentials that drive the fluxes of their respective conjugate molar quantities in the combined law of thermodynamics including the contributions from internal processes. Various cross phenomena are discussed in terms of the present theory.

We report the use of suboxide molecular-beam epitaxy (S-MBE) to grow β-Ga2O3 at a growth rate of ∼1 µm/h with control of the silicon doping concentration from 5 × 1016 to 1019 cm−3. In S-MBE, pre-oxidized gallium in the form of a molecular beam that is 99.98% Ga2O, i.e., gallium suboxide, is supplied. Directly supplying Ga2O to the growth surface bypasses the rate-limiting first step of the two-step reaction mechanism involved in the growth of β-Ga2O3 by conventional MBE. As a result, a growth rate of ∼1 µm/h is readily achieved at a relatively low growth temperature (Tsub ≈ 525 °C), resulting in films with high structural perfection and smooth surfaces (rms roughness of

Ampelopsis grossedentata (AG) is mainly distributed in Chinese provinces and areas south of the Yangtze River Basin. It is mostly concentrated or scattered in mountainous bushes or woods with high humidity. Approximately 57 chemical components of AG have been identified, including flavonoids, phenols, steroids and terpenoids, volatile components, and other chemical components. In vitro studies have shown that the flavone of AG has therapeutic properties such as anti-bacteria, anti-inflammation, anti-oxidation, enhancing immunity, regulating glucose and lipid metabolism, being hepatoprotective, and being anti-tumor with no toxicity. Through searching and combing the related literature, this paper comprehensively and systematically summarizes the research progress of AG, including morphology, traditional and modern uses, chemical composition and structure, and pharmacological and toxicological effects, with a view to providing references for AG-related research.

Abstract Forming metallurgical phases has a critical impact on the performance of dissimilar materials joints. Here, we shed light on the forming mechanism of equilibrium and non-equilibrium intermetallic compounds (IMCs) in dissimilar aluminum/steel joints with respect to processing history (e.g., the pressure and temperature profiles) and chemical composition, where the knowledge of free energy and atomic diffusion in the Al–Fe system was taken from first-principles phonon calculations and data available in the literature. We found that the metastable and ductile (judged by the presently predicted elastic constants) Al6Fe is a pressure (P) favored IMC observed in processes involving high pressures. The MoSi2-type Al2Fe is brittle and a strong P-favored IMC observed at high pressures. The stable, brittle η-Al5Fe2 is the most observed IMC (followed by θ-Al13Fe4) in almost all processes, such as fusion/solid-state welding and additive manufacturing (AM), since η-Al5Fe2 is temperature-favored, possessing high thermodynamic driving force of formation and the fastest atomic diffusivity among all Al–Fe IMCs. Notably, the ductile AlFe3, the less ductile AlFe, and most of the other IMCs can be formed during AM, making AM a superior process to achieve desired IMCs in dissimilar materials. In addition, the unknown configurations of Al2Fe and Al5Fe2 were also examined by machine learning based datamining together with first-principles verifications and structure predictions. All the IMCs that are not P-favored can be identified using the conventional equilibrium phase diagram and the Scheil-Gulliver non-equilibrium simulations.

Abstract In situ growth of pyrochlore iridate thin films has been a long-standing challenge due to the low reactivity of Ir at low temperatures and the vaporization of volatile gas species such as IrO3(g) and IrO2(g) at high temperatures and high P O2. To address this challenge, we combine thermodynamic analysis of the Pr-Ir-O2 system with experimental results from the conventional physical vapor deposition (PVD) technique of co-sputtering. Our results indicate that only high growth temperatures yield films with crystallinity sufficient for utilizing and tailoring the desired topological electronic properties and the in situ synthesis of Pr2Ir2O7 thin films is fettered by the inability to grow with P O2 on the order of 10 Torr at high temperatures, a limitation inherent to the PVD process. Thus, we suggest techniques capable of supplying high partial pressure of key species during deposition, in particular chemical vapor deposition (CVD), as a route to synthesis of Pr2Ir2O7.

A data identifier (DID) is an essential tag or label in all kinds of databases—particularly those related to integrated computational materials engineering (ICME), inheritable integrated intelligent manufacturing (I3M), and the Industrial Internet of Things. With the guidance and quick acceleration of the development of advanced materials, as envisioned by official documents worldwide, more investigations are required to construct relative numerical standards for material informatics. This work proposes a universal DID format consisting of a set of build chains, which aligns with the classical form of identifier in both international and national standards, such as ISO/IEC 29168-1:2000, GB/T 27766–2011, GA/T 543.2–2011, GM/T 0006–2012, GJB 7365–2011, SL 325–2014, SL 607–2018, WS 363.2–2011, and QX/T 39–2005. Each build chain is made up of capital letters and numbers, with no symbols. Moreover, the total length of each build chain is not restricted, which follows the formation of the Universal Coded Character Set in the international standard of ISO/IEC 10646. Based on these rules, the proposed DID is flexible and convenient for extending and sharing in and between various cloud-based platforms. Accordingly, classical two-dimensional (2D) codes, including the Hanxin Code, Lots Perception Matrix (LP) Code, Quick Response (QR) code, Grid Matrix (GM) code, and Data Matrix (DM) Code, can be constructed and precisely recognized and/or decoded by either smart phones or specific machines. By utilizing these 2D codes as the fingerprints of a set of data linked with its cloud-based platforms, progress and updates in the composition–processing–structure–property–performance workflow process can be tracked spontaneously, paving a path to accelerate the discovery and manufacture of advanced materials and enhance research productivity, performance, and collaboration.

Understanding the interactions between solute atoms and crystalline defects is essential for determining alloy properties. Here the authors use a linear regression model to propose a quantitative correlation between local electronic structure descriptors and the solute-defect interaction energies in bcc refractory alloys.

This paper introduces a growth method—suboxide molecular-beam epitaxy (S-MBE)—which enables a drastic enhancement in the growth rates of Ga2O3 and related materials to over 1 μm h−1 in an adsorption-controlled regime, combined with excellent crystallinity. Using a Ga + Ga2O3 mixture with an oxygen mole fraction of x(O) = 0.4 as an MBE source, we overcome kinetic limits that had previously hampered the adsorption-controlled growth of Ga2O3 by MBE. We present growth rates up to 1.6 μm h−1 and 1.5 μm h−1 for Ga2O3/Al2O3 and Ga2O3/Ga2O3 structures, respectively, with very high crystalline quality at unparalleled low growth temperature for this level of perfection. We combine thermodynamic knowledge of how to create molecular beams of targeted suboxides with a kinetic model developed for the S-MBE of III–VI compounds to identify appropriate growth conditions. Using S-MBE, we demonstrate the growth of phase-pure, smooth, and high-purity homoepitaxial Ga2O3 films that are thicker than 4.5 μm. With the high growth rate of S-MBE, we anticipate a significant improvement to vertical Ga2O3-based devices. We describe and demonstrate how this growth method can be applied to a wide range of oxides. With respect to growth rates and crystalline quality, S-MBE rivals leading synthesis methods currently used for the production of Ga2O3-based devices.

Magnetic behavior and disproportionation effect of nickelates are closely related to the nature of their ground state. In the present work, the magnetic structure, lattice dynamics, electronic properties, and disproportionation effect of yttrium nickelate (YNiO3) in its ground state P21/n structure were investigated by first-principles and phonon calculations based on density functional theory (DFT). The strong correlated interactions were treated by the DFT + U approach and the meta-generalized-gradient approximation approach implemented under the strongly constrained appropriately normed functional. The S-type antiferromagnetic insulating ground state of YNiO3 was captured well by both approaches. The disproportionation effect is quantitatively characterized through the Born effective charge, indicating the ligand-hole picture of Ni2+ → Ni2−δ+ Ni2+δ with δ = 0.3. The predicted phonon frequency at the Γ point agrees well with the measured value from infrared experiments, including the longitudinal and transverse optical splitting. The analysis based on stretching force constants indicated that the interaction between Ni and O atoms in the small nonmagnetic NiO6 octahedral clusters is stronger than that in the large magnetic NiO6 octahedral clusters.

We have conducted a comprehensive thermodynamic analysis of the volatility of 128 binary oxides to evaluate their suitability as source materials for oxide molecular-beam epitaxy (MBE). 16 solid or liquid oxides are identified that evaporate nearly congruently from stable oxide sources to gas species: As2O3, B2O3, BaO, MoO3, OsO4, P2O5, PbO, PuO2, Rb2O, Re2O7, Sb2O3, SeO2, SnO, ThO2, Tl2O, and WO3. An additional 24 oxides could provide molecular beams with dominant gas species of CeO, Cs2O, DyO, ErO, Ga2O, GdO, GeO, HfO, HoO, In2O, LaO, LuO, NdO, PmO, PrO, PuO, ScO, SiO, SmO, TbO, Te2O2, U2O6, VO2, and YO2. The present findings are in close accord with available experimental results in the literature. For example, As2O3, B2O3, BaO, MoO3, PbO, Sb2O3, and WO3 are the only oxides in the ideal category that have been used in MBE. The remaining oxides deemed ideal for MBE awaiting experimental verification. We also consider two-phase mixtures as a route to achieve the desired congruent evaporation characteristic of an ideal MBE source. These include (Ga2O3 + Ga) to produce a molecular beam of Ga2O(g), (GeO2 + Ge) to produce GeO(g), (SiO2 + Si) to produce SiO(g), (SnO2 + Sn) to produce SnO(g), etc.; these suboxide sources enable suboxide MBE. Our analysis provides the vapor pressures of the gas species over the condensed phases of 128 binary oxides, which may be either solid or liquid depending on the melting temperature.

Aryl carboxylic acids are stable and readily available in great structural diversity both from natural and well-established synthetic procedures, which make them promising starting materials in organic synthesis. The conversion of benzoic acids into high-value molecules is of great importance and have gained much interest of synthetic chemists. The recent development of single-electron (1e−) activation strategy has been esteemed as a complementary method for the transformation of benzoic acids. In this context, carboxylate groups can be selectively transferred into reactive aryl carboxylic radical, aryl radical, and acyl radical by electrocatalysis, photocatalysis, or in the presence of some SET oxidants. Based on these radical species, remarkable advancements have been achieved for the rapid formation of various chemical bonds over the past 10 years. In this review, we summarize recent advances in single electron activation of aryl carboxylic acids, with an emphasis on reaction scope, catalytic system, limitation, and underlying reaction mechanism.

Silica (SiOx) thin films are promising for a wide range of applications, including catalysis, separation technology, biomedicine, or transparent super-hydrophilic films. Here, we present a study demonstrating a unique way of producing ultra-thin, freestanding silica films via silicon etching. This method utilizes silicon wafers with thermally oxidized surfaces and two common inorganic elements (sulfur and tellurium), which leads to high-rate chemical etching of the Si substrate, leaving behind freestanding silica layers. Thermodynamic calculations of the tellurium–silicon–sulfur (Te–Si–S) ternary phase diagram suggest that the removal of the Si substrate from the silica layers is due to chemical reactions that result in liquid/vapor formation of Si–S and Si–Te phases. Importantly, the chemical and physical properties of the silica film post-etch are comparable to those of the starting material. The process described here provides a route to produce large area, flexible glass substrates with widely tunable thicknesses from tens to thousands of nanometers.

An integrated experimental and computational approach has been adopted to investigate the formation mechanism of intermetallic compounds (IMCs) in dissimilar Al-Cu joints processed by vaporizing foil actuator welding (VFAW). Aiming to understand the formation of IMCs and their transition, the present work employed first-principles calculations of thermodynamic properties as a function of temperature and pressure together with diffusivities of Al and Cu from the literature. Agreeing with experimental observations, the predicted IMC formation sequence in the low-energy welding region is as follows. θ-Al2Cu forms first due to the fast diffusivity of Cu in the Al-matrix. θ-Al2Cu then transforms to η2-AlCu because of the fast diffusivities of Al/Cu in θ-Al2Cu. In the high-energy welding region, the stable γ1-Al4Cu9 and the metastable θ’’-Al3Cu are also formed in addition to the aforementioned θ-Al2Cu and η2-AlCu. η2-AlCu and considerable γ1-Al4Cu9 are the major phases in the high-energy welding region. The present approach, combining experiments and calculations, is proven to be a practical way to understand non-equilibrium metallurgical processes, as demonstrated through the study of VFAW Al-Cu joints. Keywords: Vaporizing foil actuator welding (VFAW), Al-Cu intermetallic compounds, Thermodynamic properties, Diffusion, First-principles and phonon calculations

The development of future generations of Ni-base superalloys will depend on a systematic understanding of how each alloying element affects the fundamental properties of Ni-base superalloys, particularly with respect to their creep behavior. First, this article presents the temperature-dependent data of all factors entering into dilute impurity diffusion for 26 Ni-X alloy systems, including atomic jump frequencies, thermodynamic parameters, and diffusivity plots. Second, this article presents the data used to calculate the relative creep rate ratios showing the effect of each of the 26 alloying elements, X, on the dilute Ni-X alloy. The dataset refers to “A comprehensive first-principles study of solute elements in dilute Ni alloys: Diffusion coefficients and their implications to tailor creep rate” by Hargather et al. [1].

Here, we show the strategies to strengthen Mg alloys through modifying the matrix by planar faults and optimizing the local lattice strain by solute atoms. The anomalous shifts of the local phonon density of state of stacking faults (SFs) and long periodic stacking-ordered structures (LPSOs) toward the high-frequency mode are revealed by HCP-FCC transformation, resulting in the increase of vibrational entropy and the decrease of free energy to stabilize the SFs and LPSOs. Through integrating bonding charge density and electronic density of states, electronic redistributions are applied to reveal the electronic basis for the ‘strengthening’ of Mg alloys.

High-entropy alloys: cluster-and-glue atoms behind exceptional properties A cluster-and-glue model of atomic arrangements explains the yield strength and mechanical response of high entropy alloys. Inspired by metallic glass, a team led by William Yi Wang at China’s Northwestern Polytechnical University and collaborators in the United States of America used molecular dynamics to build different atomic arrangements of refractory high entropy alloys consisting of four or more elements. Depending on atomic size and the periodic table group of each atom, some atoms organized into clusters while others glued the clusters together. Chemical bonds broke and formed with plastic deformation as the alloys went from one atomic arrangement to another via the glue atoms, causing defect avalanches explaining the serrated mechanical response of high entropy alloys. Taking into account atomic arrangement may thus help us predict the properties of high entropy alloys.

Owing to exploring the influence of the N atoms ordering in Ta2N compounds on their properties, the stability, elastic, and electronic properties of Ta2N compounds (Ta2N-I: P3¯ml and Ta2N-II: P3¯1m) were investigated using first-principles calculations based on density functional theory. Ta2N-II is energetically favorable according to the enthalpy of formation. Elastic constants were employed to reveal the stronger resistance to deformation, but weaker anisotropy, in Ta2N-II. A ductile-brittle transition was found between Ta2N-I (ductile) and Ta2N-II (brittle). The partial density of states showed a stronger orbital hybridization of Ta-d and N-p in Ta2N-II, resulting in stronger covalent bonding. The charge density difference illustrated the interaction of the Ta-N bond and electron distribution of Ta2N.

Diffusion coefficients of alloying elements in Mg are critical for the development of new Mg alloys for lightweight applications. Here we present the data set of the temperature-dependent dilute tracer diffusion coefficients for 47 substitutional alloying elements in hexagonal closed packed (hcp) Mg calculated from first-principles calculations based on density functional theory (DFT) by combining transition state theory and an 8-frequency model. Benchmark for the DFT calculations and systematic comparison with experimental diffusion data are also presented. The data set refers to “Diffusion coefficients of alloying elements in dilute Mg alloys: A comprehensive first-principles study” by Zhou et al. [1].

Visible light photocatalytic radical carbonylation has been established as a robust tool for the efficient synthesis of carbonyl-containing compounds. Acyl radicals serve as the key intermediates in these useful transformations and can be generated from the addition of alkyl or aryl radicals to carbon monoxide (CO) or various acyl radical precursors such as aldehydes, carboxylic acids, anhydrides, acyl chlorides or α-keto acids. In this review, we aim to summarize the impact of visible light-induced acyl radical carbonylation reactions on the synthesis of oxygen and nitrogen heterocycles. The discussion is mainly categorized based on different types of acyl radical precursors.

Epitaxial SrRuO3 and CaRuO3 films were grown under an excess flux of elemental ruthenium in an adsorption-controlled regime by molecular-beam epitaxy (MBE), where the excess volatile RuOx (x = 2 or 3) desorbs from the growth front leaving behind a single-phase film. By growing in this regime, we were able to achieve SrRuO3 and CaRuO3 films with residual resistivity ratios (ρ300 K/ρ4 K) of 76 and 75, respectively. A combined phase stability diagram based on the thermodynamics of MBE (TOMBE) growth, termed a TOMBE diagram, is employed to provide improved guidance for the growth of complex materials by MBE.

Epitaxial La-doped BaSnO3 films were grown in an adsorption-controlled regime by molecular-beam epitaxy, where the excess volatile SnOx desorbs from the film surface. A film grown on a (001) DyScO3 substrate exhibited a mobility of 183 cm2 V−1 s−1 at room temperature and 400 cm2 V−1 s−1 at 10 K despite the high concentration (1.2 × 1011 cm−2) of threading dislocations present. In comparison to other reports, we observe a much lower concentration of (BaO)2 Ruddlesden-Popper crystallographic shear faults. This suggests that in addition to threading dislocations, other defects—possibly (BaO)2 crystallographic shear defects or point defects—significantly reduce the electron mobility.

The pycalphad software package is a free and open-source Python library for designing thermodynamic models, calculating phase diagrams and investigating phase equilibria using the CALPHAD method. It provides routines for reading thermodynamic databases and solving the multi-component, multi-phase Gibbs energy minimization problem. The pycalphad software project advances the state of thermodynamic modeling by providing a flexible yet powerful interface for manipulating CALPHAD data and models. The key feature of the software is that the thermodynamic models of individual phases and their associated databases can be programmatically manipulated and overridden at run-time without modifying any internal solver or calculation code. Because the models are internally decoupled from the equilibrium solver and the models themselves are represented symbolically, pycalphad is an ideal tool for CALPHAD database development and model prototyping.

High-throughput measurement using the numerical inverse method combined with the diffusion multiple technique was employed to determine the composition-dependent interdiffusion coefficients in fcc Al–Co–Cr–Fe–Ni high-entropy alloys at 1273, 1323, and 1373 K. The reliability of the obtained interdiffusion coefficients was confirmed by comparing the model-predicted composition/interdiffusion flux profiles with the experimental data. The tracer diffusivities of the components were then predicted based on the obtained interdiffusion coefficients and the simplified thermodynamic description. The diagonal interdiffusion coefficients in the present high-entropy alloys were comprehensively compared with those in conventional fcc alloys. Therefore, the sluggish diffusion effect does not apply for all the elements in the present fcc Al–Co–Cr–Fe–Ni high-entropy alloys. A similar result was also observed for the evaluated tracer diffusivities.

A thermodynamic database for the Al–Co–Cr–Ni system is built via the Calphad method by extrapolating re-assessed ternary subsystems. A minimum number of quaternary parameters are included, which are optimized using experimental phase equilibrium data obtained by electron probe micro-analysis and x-ray diffraction analysis of NiCoCrAlY alloys spanning a wide compositional range, after annealing at 900 °C, 1100 °C and 1200 °C, and water quenching. These temperatures are relevant to oxidation and corrosion resistant MCrAlY coatings, where M corresponds to some combination of nickel and cobalt. Comparisons of calculated and measured phase compositions show excellent agreement for the β–γ equilibrium, and good agreement for three-phase β–γ–σ and β–γ–α equilibria. An extensive comparison with existing Ni-base databases (TCNI6, TTNI8, NIST) is presented in terms of phase compositions.

The phase relations and thermodynamic properties of the condensed Al-Co-Cr ternary alloy system are investigated using first-principles calculations based on density functional theory (DFT) and phase-equilibria experiments that led to X-ray diffraction (XRD) and electron probe micro-analysis (EPMA) measurements. A thermodynamic description is developed by means of the calculations of phase diagrams (CALPHAD) method using experimental and computational data from the present work and the literature. Emphasis is placed on modeling the bcc-A2, B2, fcc-γ, and tetragonal-σ phases in the temperature range of 1173 to 1623 K. Liquid, bcc-A2 and fcc-γ phases are modeled using substitutional solution descriptions. First-principles special quasirandom structures (SQS) calculations predict a large bcc-A2 (disordered)/B2 (ordered) miscibility gap, in agreement with experiments. A partitioning model is then used for the A2/B2 phase to effectively describe the order-disorder transitions. The critically assessed thermodynamic description describes all phase equilibria data well. A2/B2 transitions are also shown to agree well with previous experimental findings.

Kinetic properties of Ni(II) in eutectic LiF-NaF-KF (FLiNaK) molten salt were determined at T = 748–823 K using cyclic voltammetry (CV), square wave voltammetry (SWV), and chronoamperometry (CA) measurements using a glassy C working electrode, Ni(II)/Ni reference electrode, and Ni counter electrode. Reduction of Ni(II) to Ni(s) was determined to be a single step, two-electron transfer process. Diffusivity values were calculated using the Berzins and Delahay equation and semi-integral electroanalysis from the CV measurements as well as using the Cottrell equation from the CA measurements. Diffusivity of Ni(II) in molten FLiNaK at T = 748–823 K was determined to be 3.27 × 10–7 –3.04 × 10–6 cm² s –1 with an activation energy of 62–104 kJ mol–1 . The estimated kinetic properties varied appreciably among methodologies possibly due to inherent assumptions in theory regarding reversibility and unit activity during Ni metal deposition on the working electrode. [ABSTRACT FROM AUTHOR]

The growth of BiFe[O.sub.3] is demonstrated on many oxide and wide bandgap semiconductor substrates by using reactive molecular beam epitaxy in an adsorption-controlled growth regime. The epitaxial integration of the ferroelectric with the highest polarization, BiFe[O.sub.3], with high bandgap semiconductors is an vital step toward novel field-effect devices.

The study focuses on transition temperature variations as a function of Ba/Ti ratio and in undoped BaTiO(sub)3 powders with particle size to understand stoichiometric effects on transition behavior when materials are processed under equilibrium conditions, before introducing additional degrees of freedom such a dopants, size effect or applied stress. It is found that all the different defects contribute to the changes of transition temperature and enthalpy of transition.

A comparative analysis was conducted between the morphological stability of growing particles and the maximum growth rate (MGR) principle. The aim of the study was to determine if both would give similar predictions for platelet growth. Results show that MGR is applicable to the growth of a platelike particle when sidebranching is nonexistent. Further analysis also revealed that for large supercooling, the MGR principle presented suitable variables whereas the morphological stability analysis tended to break down.

The thermochemical properties of Sr-Sn alloys were determined by electromotive force (emf) measurements to evaluate liquid tin as an interacting electrode material for separating alkaline-earth elements from molten salt solutions. A Sr(s)|CaF2-SrF2|Sr(in Sn) cell was used to measure emf values for twelve Sr-Sn alloys at mole fractions xSr = 0.02-0.43, allowing the determination of thermochemical properties such as activity and partial molar quantities of Gibbs energy, entropy, and enthalpy of Sr at 730-1110 K. Activity values of Sr in liquid Sn were as low as 6.9 × 10-12 at 800 K and xSr = 0.02 indicating highly non-ideal solution behavior between Sr and Sn. Phase transitions were also determined from the emf data and were validated via differential scanning calorimetry (DSC). Through the combination of emf measurements for thermochemical properties, X-ray diffraction (XRD) for phase constituents, and DSC measurements for phase transitions, this work established more complete thermodynamic properties of the Sr-Sn binary system. [ABSTRACT FROM AUTHOR]

Exploration of longstanding issues in magnetic materials, for example the nature of Curie/Néel temperature and the Schottky anomaly of heat capacity, appeals to reliable models at finite temperatures. Based on first-principles calculations and partition function approach with the microstates being the collinear magnetic configurations, the magnetic thermodynamics of fcc Ni, including the heat capacity and the pressure-dependent Curie temperature, is predicted well and compared with the results from experiments and mean-field approach. As demonstrated in fcc Ni, it is found that the magnetic thermodynamics containing anomalies stems from the magnetic configurational entropy caused by the competition of various magnetic states. [ABSTRACT FROM AUTHOR]

The anisotropy of antiphase boundary (APB) energies in ordered L12-Ni3Al is studied, owing to its importance in understanding the anomalous flow behavior of this intermetallic compound. We report first-principle calculations for two types of APBs in the ordered compound: (001) and (111). The magnetic perturbations associated with these APBs are calculated as a function of supercell size to ensure that their periodic images are isolated both magnetically and elastically. The magnetic perturbation associated with the (111) APB is wider than that of the (001) APB. The fully relaxed, spin-polarized APB energies for (001) and (111) APBs are calculated to be 82 mJ/m2 and 177 mJ/m2, respectively. The resulting anisotropy ratio of σ(111)/σ(001)=2.16, which is significantly higher than previously reported values, suggests that cross-slip between (001) and (111) is highly favorable. [ABSTRACT FROM AUTHOR]

Several first-principles calculations are conducted to determine the anisotropy of the antiphase boundary (APB) energies exhibited by the ordered [Ni.sub.3]Al compound. The magnetic perturbation associated with (111) APB is shown to be much wider than the (001) APB.

The effect of equilibrated nonstoichiometry on the ferroelectric properties of the perovskite BaTi[O.sub.3] is studied. The results have illustrated the strong sensitivity of the Landau coefficients characterizing the properties of the monodomain ferroelectric state to nonstoichiometry involving partial Schottky disorder reactions in the perovskite-structured oxides.

Although the peak power density of anion exchange membrane fuel cells (AEMFCs) has been raised from ˜0.1 to ˜1.4 W cm-2 over the last decade, a majority of AEMFCs reported in the literature have not been demonstrated to achieve consistently high performance and steady-state operation. Poly(olefin)-based AEMs with fluorine substitution on the aromatic comonomer show considerably higher dimensional stability compared to samples that do not contain fluorine. More importantly, fluorinated poly(olefin)-based AEMs exhibit high hydroxide conductivity without excessive hydration due to a new proposed mechanism where the fluorinated dipolar monomer facilitates increased hydroxide dissociation and transport. Using this new generation of AEMs, a stable, high-performance AEMFC is operated for 120 h. When the fuel cell configuration is subjected to a constant current density of 600 mA cm-2 under H2/O2 flow, the cell voltage declines only 11% (from 0.75 to 0.67 V) for the first 20 h during break-in and the cell voltage loss is low (0.2 mV h-1) over the subsequent 100 h of cell testing. The ease of synthesis, potential for low-cost commercialization, and remarkable ex situ properties and in situ performance of fluoropoly(olefin)-based AEM renders this material a benchmark membrane for practical AEMFC applications. [ABSTRACT FROM AUTHOR]

Epitaxial La-doped BaSnO3 films were grown in an adsorption-controlled regime by molecular-beam epitaxy, where the excess volatile SnOx desorbs from the film surface. A film grown on a (001) DyScO3 substrate exhibited a mobility of 183 cm² V-1 s-1 at room temperature and 400 cm² V-1 s-1 at 10 K despite the high concentration (1.2 × 1011 cm-2) of threading dislocations present. In comparison to other reports, we observe a much lower concentration of (BaO)2 Ruddlesden-Popper crystallographic shear faults. This suggests that in addition to threading dislocations, other defects-- possibly (BaO)2 crystallographic shear defects or point defects--significantly reduce the electron mobility. [ABSTRACT FROM AUTHOR]

Thermal expansion is an important property of substances. Its theoretical prediction has been challenging, particularly in cases the volume decreases with temperature, i.e., thermal contraction or negative thermal expansion at high temperatures. In this paper, a new theory recently developed by the authors has been reviewed and further examined in the framework of fundamental thermodynamics and statistical mechanics. Its applications to cerium with colossal thermal expansion and Fe3Pt with thermal contraction in certain temperature ranges are discussed. It is anticipated that this theory is not limited to volume only and can be used to predict a wide range of properties at finite temperatures. [ABSTRACT FROM AUTHOR]

Precursor modulations often occur in functional materials like magnetic shape memory alloys, ferroelectrics, and superconductors. In this letter, we have revealed the underlying mechanism of the precursor modulations in ferromagnetic shape memory alloys Ni2MnGa by combining synchrotron-based x-ray diffraction experiments and first-principles phonon calculations. We discovered the precursor modulations along [011] direction can be eliminated with [001] uniaxial loading, while the precursor modulations or premartensite can be totally suppressed by hydrostatic pressure condition. The TA2 phonon anomaly is sensitive to stress induced lattice strain, and the entire TA2 branch is stabilized along the directions where precursor modulations are eliminated by external stress. Our discovery bridges precursor modulations and phonon anomalies, and sheds light on the microscopic mechanism of the two-step superelasticity in precursor martensite. [ABSTRACT FROM AUTHOR]

In this study, amorphous lithium lanthanum titanate (LLTO) powders were prepared by a sol-gel method with an all alkoxide based route. Results showed that unlike its crystalline counterpart which turns into an electronic conductor in direct contact with lithium metal, amorphous LLTO remains to be an ionic conductor and hence is compatible with lithium metal as solid electrolyte although it also undergoes lithium insertion and the consequent reduction of Ti4+ to Ti3+. This striking difference between crystalline and amorphous LLTO could be ascribed to the atomic configuration difference, ordered versus disordered. The electronic states of a disordered system could be localized. It was found that the transference number of lithium ions of amorphous LLTO is over 82%. Our results on electrochemical measurements indicated that amorphous LLTO is stable with blocking electrodes up to 12 V, which can potentially be used with high voltage cathode materials. [ABSTRACT FROM AUTHOR]

Thermal expansion, defined as the temperature dependence of volume under constant pressure, is a common phenomenon in nature and originates from anharmonic lattice dynamics. However, it has been poorly understood how thermal expansion can show anomalies such as colossal positive, zero, or negative thermal expansion (CPTE, ZTE, or NTE), especially in quantitative terms. Here we show that changes in configurational entropy due to metastable micro(scopic)states can lead to quantitative prediction of these anomalies. We integrate the Maxwell relation, statistic mechanics, and first-principles calculations to demonstrate that when the entropy is increased by pressure, NTE occurs such as in Invar alloy (Fe3Pt, for example), silicon, ice, and water, and when the entropy is decreased dramatically by pressure, CPTE is expected such as in anti-Invar cerium, ice and water. Our findings provide a theoretic framework to understand and predict a broad range of anomalies in nature in addition to thermal expansion, which may include gigantic electrocaloric and electromechanical responses, anomalously reduced thermal conductivity, and spin distributions. [ABSTRACT FROM AUTHOR]