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The elucidation of governing principles of catalyst activity from fundamental research on well-defined model systems, combined with the advances in controlled synthesis of the transition metal nanocatalysts, have led to the rational design and development of advanced nanocatalysts. One principle is to tune surface strain and thereby modulate the surface electronic structure and catalytic reactivity. This approach has been employed to identify transition metal and (hydroxy)oxide catalysts for energy-relevant electrocatalytic reactions. For oxygen reduction reaction on platinum as an example, previous studies have indicated that a 1% compressive strain may improve the activity over 300%. While strain tuning of catalysts is very promising for activity enhancement, two challenges continue to limit the performance of these materials. First, the effect of strain on high-surface-area nanoparticle catalysts is often convoluted with nanoparticle shape and by the presence of undercoordinated defects, while model catalysts, where high specific activities is achievable by strain tuning, have prohibitively small mass activities and are therefore of limited practical interest. Thus, there is an urgent need to develop strain tuning strategies for nanomaterials that preserve the structural simplicity and high specific activity of single crystals while simultaneously possessing high surface areas and mass activities. In addition, strain in catalyst overlayers is often imposed by heterosubstrates, which may lead to interfacial reconstructions and strain release. In this talk, in combination DFT calculations, electrochemical tests and TEM characterization, we will present a strategy to resolve these problems through self-driven strain tuning in transition metal nanocrystals with the characteristics of low-index single-crystal surfaces. As we demonstrate for the oxygen reduction reaction in alkaline fuel cells, this relationship could be exploited to enhance reaction rates by orders of magnitude in comparison with nanoparticle catalysts, suggesting that this self-driven tuning mechanism in transition metal nanocrystals can be a powerful strategy for the design and development of advanced catalytic materials.

Nitrogen cycle electrochemistry is an emerging area of interest in the electrocatalysis community, with applications ranging from removal of nitrates from wastewater streams to the development of fundamental understanding of NO electrochemistry. In spite of a significant amount of fundamental research for this chemistry on single crystal surfaces, however, the mechanistic details of the reactions are not fully known, and even such basic information as the nature of the rate-limiting step is not understood. In this work, we apply some of the innovations in theoretical electrochemistry that have emerged over the past 5-10 years to the study of NO and nitrate reduction on transition metal surfaces. We begin with a simple Density Functional Theory analysis of direct NO reduction in acid on Pt(111), Pt(100), and Pt(211) surfaces, and we identify potential- and rate-determining steps on each surface, using extensive ab-initio molecular dynamics simulations to estimate the impact of the aqueous environment on surface thermodynamics and kinetics (Ang. Chem. Int. Ed. 2015). We next introduce a novel approach that couples DFT calculations with rigorous kinetic Monte Carlo (kMC) simulations to understand, in unprecedented detail, the effect of higher adsorbed NO coverages on these chemistries, and we demonstrate that these coverage-dependent effects are essential for describing experimentally measured polarization curves (ACS Catalysis 2017). We subsequently generalize our analysis by developing universal Brønsted-Evans-Polanyi relationships that rigorously relate barriers for proton-coupled electron transfer to surface species to the corresponding thermodynamics across a large space of different transition metals and potentials. These relationships, combined with the potential- and coverage-dependent energetics determined on platinum, provide a basis to extrapolate our mechanistic analyses to other transition metals, including PtSn and related alloys. We employ these techniques to propose design strategies to tune selectivity of NO electroreduction to desired products, including N2 and hydroxylamine, on these different transition metals and alloys. If time permits, we will briefly describe some additional work on the development of structural and catalytic reactivity models at the interface between thin hydroxyoxide films and precious metal platinum substrates. We will examine the kinetics of the hydrogen evolution reaction as a function of the structure and oxidation state of these interfaces and will demonstrate that the bifunctional nature of the interfaces plays a key role in their electrocatalytic properties.

Combined with third generation synchrotron radiation light sources, X-ray photoelectron spectroscopy (XPS) with higher energy resolution, brilliance, enhanced surface sensitivity and photoemission cross section in real time found extensive applications in solid-gas interface chemistry. This paper reports the calculation of the core-level binding energy shifts (CLS) using the first-principles density functional theory. The interplay between the CLS calculations and XPS measurements to uncover the structures, adsorption sites and chemical reactions in complex surface chemical processes are highlight. Its application on clean low index (111) and vicinal transition metal surfaces, molecular adsorption in terms of sites and configuration, and reaction kinetics are domonstrated.

By a metastable rocksalt ZnO interfacial structure and a resulting rocksalt-to-wurtzite structure transition in ZnO buffer layer, polarity control of Zn-polar ZnO films was realized on rocksalt MgO (1 1 1) template by plasma-assisted molecular beam epitaxy. The metastable rocksalt ZnO and the phase transition from octahedrally bonded rocksalt to tetrahedrally bonded wurtzite structure during the growth of ZnO buffer layer were established by the combination of in situ reflection high-energy electron diffraction and ex situ high-resolution transmission electron microscopy. Such a metastable rocksalt ZnO has a lattice constant a = 4.16 angstrom and a typical ...abcabc... atom stacking along the growth direction. Polarity selection of Zn-polar ZnO films was found greatly depending on the bonding configuration of the epitaxial ZnO interfacial layer, and an atomic model of the structure transition was proposed to explain the mechanism of ZnO polarity selection. (C) 2009 Elsevier B.V. All rights reserved.

The role of subsurface oxygen in Ag(111) and the step edge of vicinal Ag(221) on CO oxidation were studied by using density functional theory calculations. For high oxygen coverage, the formation of subsurface oxygen is not only energetically favorable but also kinetically likely. CO oxidation with on-surface atomic oxygen is facile with a barrier of about 0.16 eV, whereas the reaction with subsurface oxygen is hindered because of the significant barrier for diffusion of the subsurface oxygen to the surface from the subsurface region. It is found that the adsorption of molecules (CO, atomic O and O2) is stabilized in the presence of subsurface oxygen, and surface reactivity is enhanced. An energetically favorable reaction pathway for CO oxidation with O2 is identified, with a reaction barrier of 0.23 eV via a unique four-center Ο2···CΟ intermediate. A catalytic cycle for CO oxidation on Ag(111) in the presence of subsurface oxygen is proposed. On Ag(221) surfaces, our calculations show that both the adsor...

Metastable structures of MgO overlayer on type-III oxide surfaces were achieved by molecular beam epitaxy. Periodic out-of-plane dipole moment of substrates was revealed to play a dominant role in the formation of metastable oxide structures. Under near-equilibrium epitaxial conditions, this dipole moment was found to drive the over-grown MgO to inherit the out-of-plane substrate lattice, resulting in some new structures with different stacking sequences and bonding configurations from those of thermodynamically stable phase. As typical cases, by adopting the substrate dipole moment along the growth direction, MgO overlayers with metastable wurtzite (WZ) and stacking-fault (SF) structures were formed on alpha-Al(2)O(3) (0001) and MgAl(2)O(4)(111) surfaces, respectively. (c) 2008 Elsevier B.V. All rights reserved.

Transmission electron microscopy has been used to investigate the (1100) and (1103) inversion domain boundaries in a ZnO film prepared by molecular beam epitaxy. The inversion domain was revealed by dark-field images and confirmed by convergent-beam electron diffraction. Interacting with a (0002) stacking fault, the inversion domain boundary in the (1100) plane alters its orientation from the [0001] direction and climbs on the (1103) plane to release the strain energy. These features are characterized and analysed by high-resolution electron microscopy and the geometric phase method. The findings are significant for understanding the formation and propagation of inverse domain boundaries in epitaxial ZnO films.

A tri-buffer method was applied to achieve layer-by-layer growth of high-quality ZnO films on sapphire (0001) substrates by rf plasma-assisted molecular beam epitaxy (MBE). After sufficient nitridation of the substrate, MgO and ZnO buffer layers were subsequently deposited on the resulting AlN layer. An atomically smooth ZnO surface with a roughness less than 1 nm in a 10 μm × 10 μm scanned area was obtained with this method. The crystal quality was also improved, as characterized by reflection high-energy electron diffraction (RHEED), x-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). The results indicate that the tri-buffer process could reduce the large lattice mismatch between ZnO and nitrided sapphire and facilitate the two-dimensional (2-D) growth of the ZnO epilayer. A model is proposed to understand the observations.

BACKGROUND: Mitochondrial injury is a major cause of sepsis-induced organ failure. Polydatin (PD), a natural polyphenol, demonstrates protective mitochondrial effects in neurons and arteriolar smooth muscle cells during severe shock. In this study, we investigated the effects of PD on renal tubular epithelial cell (RTEC) mitochondria in a rat model of sepsis-induced acute kidney injury. METHODS: Rats underwent cecal ligation and puncture (CLP) to mimic sepsis-induced acute kidney injury. Rats were randomly divided into sham, CLP + normal saline, CLP + vehicle, and CLP + PD groups. Normal saline, vehicle, and 30 mg/kg PD were administered at 6, 12, and 18 hours after CLP or sham surgery via the tail vein. Mitochondrial morphology, metabolism, and function in RTECs were then assessed. Serum cytokines, renal function, survival, and histologic changes in the kidney were also evaluated. RESULTS: CLP increased lipid peroxide content, lysosomal instability, and opening of the mitochondrial permeability transition pore and caused mitochondrial swelling. Moreover, mitochondrial membrane potential (ΔΨm) was decreased and ATP levels reduced after CLP. PD inhibited all the above effects. It also inhibited the inflammatory response, improved renal function, attenuated histologic indicators of kidney damage, and prolonged survival. CONCLUSIONS: PD protects RTECs against mitochondrial dysfunction and prolongs survival in a rat model of sepsis-induced acute kidney injury. These effects may partially result from reductions in interleukin-6 and oxidative stress.

Background Despite resuscitation after trauma, microcirculatory abnormalities are known to persist in post-shock multiorgan dysfunction. The high-molecular weight polymer polyethylene oxide (PEO) (>106 Da), a classic drag-reducing polymer, can improve hemorrhagic shock (HS)–induced hemodynamic abnormalities in rats. Materials and methods We examined the effects of PEO on microcirculation and on changes in multiple organs after shock. After the spinotrapezius muscle was prepared, HS was induced in Sprague–Dawley rats. Drug administration (normal saline or PEO) was performed 2 h after shock followed by infusion of shed blood. Results The velocity, blood flow, and functional capillary density in the shock + PEO group were significantly higher than those in the shock + normal saline group. Moreover, the kidney, liver, and lung function was improved, resulting in prolonged survival time. Our findings indicate that intravenous infusion of PEO can ameliorate shock-associated organ dysfunction and prolong survival time in severe HS, which may be a result of increased arteriolar blood velocity, blood flow, and functional capillary density. Conclusions PEO could have potential clinical application in the treatment of shock-induced multiorgan dysfunction.

Introduction Neutrophil gelatinase-associated lipocalin (NGAL), cystatin C (Cys-C), and soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) are novel diagnostic biomarkers of acute kidney injury (AKI). We aimed to determine the diagnostic properties of these biomarkers for detecting AKI in critically ill patients with sepsis. Methods We divided 112 patients with sepsis into non-AKI sepsis (n = 57) and AKI sepsis (n = 55) groups. Plasma and urine specimens were collected on admission and every 24 hours until 72 hours and tested for NGAL, Cys-C, and TREM-1 concentrations. Their levels were compared on admission, at diagnosis, and 24 hours before diagnosis. Results Both plasma and urine NGAL, Cys-C, and sTREM-1 were significantly associated with AKI development in patients with sepsis, even after adjustment for confounders by using generalized estimating equations. Compared with the non-AKI sepsis group, the sepsis AKI group exhibited markedly higher levels of these biomarkers at diagnosis and 24 hours before AKI diagnosis (P Conclusion Plasma and urine NGAL, Cys-C, and sTREM-1 can be used as diagnostic and predictive biomarkers for AKI in critically ill patients with sepsis.

Background Polydatin (PD), a monocrystalline and polyphenolic drug isolated from a traditional Chinese herb (Polygonum cuspidatum), is protective against mitochondrial dysfunction and has been approved for clinical trials in the treatment of shock. However, whether the administration of PD has a therapeutic effect on multiple-organ dysfunction syndrome (MODS) requires investigation. Material and methods MODS was induced in Sprague–Dawley rats via hemorrhage and ligation and puncture of cecum–induced sepsis. The rats were divided into three groups as follows: MODS + PD, MODS + normal saline, and a control group (no treatment). Survival time, blood biochemical indexes, and histopathologic changes in various organs were evaluated; serum oxidative stress (advanced oxidative protein products [AOPPs]) and proinflammatory cytokines (tumor necrosis factor-α, interleukin 1β, and interleukin 6) were assayed using enzyme-linked immunosorbent assay. Apoptosis-related protein expression (B-cell lymphoma-2 [Bcl-2] and Bax) was assayed by immunohistochemical and Western blotting methods, whereas caspase-3 activity was assayed by spectrophotometry. Results PD improved organ function, prolonged survival time, and reduced MODS incidence and serum levels of AOPPs and proinflammatory cytokines. It also decreased Bax levels and caspase-3 activity and increased Bcl-2 levels in the kidney and liver. Conclusions PD may serve as a potential therapeutic for MODS, as it suppresses oxidative stress, inhibits inflammatory response, attenuates apoptosis, and protects against mitochondrial dysfunction.

Three kinds of nozzles normally used in industrial production are numerically simulated, and the structure of nozzle with the best jetting performance out of the three nozzles is optimized. TheR90 nozzle displays the most optimal jetting properties, including the smooth transition of the nozzle’s inner surface. Simulation results of all sample nozzles in this study show that the helix nozzle ultimately displays the best jetting performance. Jetting velocity magnitude alongYandZcoordinates is not symmetrical for the helix nozzle. Compared to simply changing the jetting angle, revolving the jet issued from the helix nozzle creates a grinding wheel on the cleaning surface, which makes not only an impact effect but also a shearing action on the cleaning object. This particular shearing action improves the cleaning process overall and forms a wider, effective cleaning range, thus obtaining a broader jet width.

We have performed the first principles calculations on doped δ-Bi2O3 to investigate ionic conductivity. The crystal structure and the ionic conductivity are discussed in total energy and density of states (DOS) from the calculations. The stabilized δ-phase Bi2O3 doped rare-earth metal was explained from DOS data. By doping Ca, Sr, La, Gd or Sm, the ion conductivity monotonically decreases, while doping with impurity Y, Tb, Dy, Er or Tm, the ion conductivity firstly increases and then decrease. Our results support the effective oxygen vacancies mechanism.

Advances in the theoretical understanding of interfacial electrochemistry have, over the past decade, permitted the extension of periodic Density Functional Theory studies, which have traditionally been applied to probe chemistry at gas/solid interfaces, to electrochemical systems where potential-dependent structural and chemical phase transformations occur at liquid/solid interfaces. Indeed, such techniques have been employed to study a surprisingly wide class of electrochemical processes, ranging from electrocatalysis to corrosion. In this talk, we will discuss how these strategies can be applied to predict the detailed, atomic-scale properties of monolayer (hydroxy)oxide base metal films on precious metal and precious metal alloy substrates as a function of applied potential. We will describe the analysis of Moire patterns, variable oxidation states, and three-phase boundaries of these films, and we will demonstrate how these results may be used to predict the shape and oxidation states of supported two-dimensional nanoislands as a function of electrochemical conditions. We will next discuss how the three-phase boundaries may promote hydrogen evolution rates in alkaline environments, and we will close with some perspectives on the possibilities for electrocatalyst design offered by these systems. If time permits, we will also discuss a new approach, based on a combination of DFT and kinetic Monte Carlo simulations, that permits direct simulation of polarization curves as a function of sweep rate and that rigorously predicts intrinsic reaction pathways for both electroreduction of nitrates and NO in acidic environments.

The Atomic Simulation Environment (ASE) is a software package written in the Python programming language with the aim of setting up, steering, and analyzing atomistic simula- tions. In ASE, tasks are fully scripted in Python. The powerful syntax of Python combined with the NumPy array library make it possible to perform very complex simulation tasks. For example, a sequence of calculations may be performed with the use of a simple “for-loop” construction. Calculations of energy, forces, stresses and other quantities are performed through interfaces to many external electronic structure codes or force fields using a uniform interface. On top of this calculator interface, ASE provides modules for performing many standard simulation tasks such as structure optimization, molecular dynamics, handling of constraints and performing nudged elastic band calculations.

Understanding the electrochemical reactions at Liquid-Solid interfaces has been a great and long-term interest but challenge for both experimentalists and theorists. Even though tremendous advances have made through numerous techniques, significant uncertainties relating to the reaction intermediates and reaction mechanism remain. The problem is further complicated when a Solid-Solid interface has been formed either through electrodeposition or de-alloying, as the corresponding interface structures and consequently surface structures of the catalysts are still largely unknown. In this talk, we will review the methodologies we have recently developed to de-convolute those effects, including a synergistic strategy towards highly accurate prediction of Pourbaix diagram of transition metal (hydroxy)oxides, a simple Morie pattern technique for screening Solid-Solid interface, ab initio molecular simulation to sample Liquid-Solid interfaces and X-ray Photoelectron Spectroscopy simulation to identify the oxygenated species at Liquid-Solid interface. Next, using monolayer layer (hydroxy)oxide-metal interface as an example, we will demonstrate how the combination of the above techniques could identify the stable phases under various electrochemical conditions. As a case study, we will show the bi-functional role of the interface in promoting hydrogen evolution reaction (HER). As another example, we will show the development of the metal-metal interface during the de-alloying process of Pt-based alloy electrocatalysts. Finally, we will show the applications of these understandings for the design of new catalysts with improved performances for electrolysis and fuel cell applications. [1] L. Wang, Y. Zhu, Z. Zeng, C. Lin, M. Giroux, L. Jiang, Y. Han, J. Greeley, C. Wang, and J. Jin, Nano Energy 31, 456 (2017). [2] Z. Zeng and J. Greeley, Nano Energy 29, 369 (2016). [3] Y. Ha, Z. Zeng, Y. Cohen, J. Greeley, and A. A. Gewirth, J. Phys. Chem. C 120, 8674 (2016). [4] Z. Zeng, M. K. Y. Chan, Z.-J. Zhao, J. Kubal, D. Fan, and J. Greeley, J. Phys. Chem. C 119, 18177 (2015).

The electrocatalytic reduction of CO2 to industrial chemicals and fuels is a promising pathway to sustainable electrical energy storage and to an artificial carbon cycle, but it is currently hindered by the low energy efficiency and low activity displayed by traditional electrode materials. We report here the size-dependent catalytic activity of micelle-synthesized Au nanoparticles (NPs) in the size range of ∼1–8 nm for the electroreduction of CO2 to CO in 0.1 M KHCO3. A drastic increase in current density was observed with decreasing NP size, along with a decrease in Faradaic selectivity toward CO. Density functional theory calculations showed that these trends are related to the increase in the number of low-coordinated sites on small NPs, which favor the evolution of H2 over CO2 reduction to CO. We show here that the H2/CO product ratio can be specifically tailored for different industrial processes by tuning the size of the catalyst particles.

Metal-insulator-metal (MIM) capacitors with atomic layer deposited (ALD) various Al 2 O 3 thicknesses are investigated for radio frequency integrated circuit (RFIC) applications. For 20 nm Al 2 O 3 , the fabricated capacitor exhibits a high capacitance density of 3850 pF/mm2 and acceptable voltage coefficients of capacitance (VCCs) of 681 ppm/V2 and 134 ppm/V at 1 MHz. An outstanding VCCs of 74 ppm/V2 and 55 ppm/V is obtained by 100 nm thickness Al 2 O 3 MIM capacitors. The impact of various dielectric thicknesses on RF characteristics such as Q factors and resonance frequency is also investigated. Moreover, a simplified small signal model of the MIM capacitors is described. Excellent agreement between measured and simulated data demonstrates the validity of this model.

In this paper, MOS capacitors and Mg-implanted source and drain p-channel GaSb MOSFETs are fabricated. The effects of post-metallization annealing (PMA) on the performance of these devices have been studied. The 30sec 300 °C PMA in N 2 ambient is found to improve the quality of the Al 2 O 3 /n-GaSb interface. After PMA, for a device with a gate length of 2µm, a maximum drive current of 10.8 mA/mm, and an I on /I off ratio of 2×103 are achieved.

Ge is a promising candidate to replace Si for advanced metal-oxide-semiconductor field effect transistors (MOSFETs) because of its high mobility. Reducing interface trap density (D it ) and forming high quality high-k/Ge gate stacks are required for high-performance Ge-MOSFET. The GeO 2 interfacial layer (IL) between high-k and Ge is considered as one of the best solutions to improve the interface quality. Therefore, in this study, various passivation ways including thermal oxidation, ozone oxidation and modified ozone oxidation were investigated. The impacts of three oxygen-related passivation methods on interface modification, gate leakage suppression, and dielectric enhancement were discussed.

In this paper, a novel InGaAs metal oxide semiconductor field effect transistor (MOSFET) radio frequency (RF) switch device is demonstrated. The MOSFET RF switch device with 0.3 µm gate length and 10 nm Al 2 O 3 as gate dielectric shows insertion loss of 0.3 dB and isolation of more than 50 dB. A maximum drain current of 250 mA/mm, a peak transconductance of 370 mS/mm, a turn-on resistance of 2.4 O·mm and a drain current on-off (I on /I off ) ratio of over 1×106 are obtained. The small signal models of this MOSFET switch device are also described. Excellent agreement between measured and simulated demonstrates the validity of this model.

INTRODUCTION: Polydatin (PD) has anti-inflammatory and anti-apoptotic effects in ischemic-reperfusion injury. Moreover, inflammatory responses and apoptosis play a role in the development of burn-induced lung injuries. Based on these findings, in this study we investigated the hypothesis that PD can ameliorate lung injury induced by extensive burns via reduction of inflammation and apoptosis. METHODS: Rats were subjected to 30% total body surface area burn injury followed by resuscitation. The treatment group received 45 mg/kg PD, and the burn group received the same amount of normal saline solution. No burn injury was inflicted in the sham group. Microvascular permeability, interstitial edema, neutrophil recruitment, and histopathological changes were detected by measuring Evans blue concentration, wet-to-dry lung weight ratio (W/D), myeloperoxidase (MPO) activity, and hematoxylin and eosin staining, respectively. To investigate the mechanism of action of PD, enzyme-linked immunosorbent assay, cell counting, terminal deoxyribonucleotidyl transferase-mediated deoxyuridine 5-triphosphate-digoxigenin nick end labeling (TUNEL) staining, fluorometric assay, and Western blot were used for assessing levels of inflammatory cytokines (tumor necrosis factor alpha, interleukin [IL]-1β, and IL-6), total number of cells, and concentration of polymorphonuclear leukocytes (PMNs) in bronchoalveolar lavage fluid (BALF), the number of apoptotic cells, caspase-3 activity, and apoptosis-related proteins including Bax and Bcl-xl, respectively. RESULTS: Burn-injury rats exhibited significant lung injury characterized by the deterioration of histopathological characteristics, pulmonary microvascular hyperpermeability, and a high W/D, which were attenuated by PD ( P = .007 for permeability, P = .004 for W/D). PD inhibited the burn-induced inflammatory response, as evidenced by the down-regulation of lung MPO activity ( P = .008), total number of cells, PMN concentration in BALF, and the local and systemic levels of the pro-inflammatory cytokines examined. Moreover, PD treatment dramatically prevented burn-induced pulmonary cell apoptosis in lungs, as reflected by the decrease in the number of TUNEL-positive cells ( P = .002) and changes in Bax, Bcl-xl, and caspase-3 activity ( P = .03). CONCLUSIONS: PD ameliorates burn-induced lung injury via its anti-inflammatory and anti-apoptotic effects, and PD treatment may therefore serve as a potential therapeutic target for the treatment of critical burn injuries.

The electronic and magnetic properties of the nanometer-size antiferromagnet [Fe(OMe${)}_{2}$(${\mathrm{O}}_{2}$${\mathrm{CCH}}_{2}$Cl)${]}_{10}$ are investigated with the first-principles spin-polarized discrete variational method, in the framework of density-functional theory. Magnetic moments, densities of states, and charge- and spin-density maps are obtained. The M\"ossbauer hyperfine parameters isomer shift, quadrupole splitting, and hyperfine field are obtained from the calculations and compared to reported experimental values when available.

Generalized trends in the formation energies of several families of perovskite oxides (ABO3) and plausible explanations to their existence are provided in this study through a combination of DFT calculations, solid-state physics analyses and simple physical/chemical descriptors. The studied elements at the A site of perovskites comprise rare-earth, alkaline-earth and alkaline metals, whereas 3d and 5d metals were studied at the B site. We also include ReO3-type compounds, which have the same crystal structure of cubic ABO3 perovskites except without A-site elements. From the observations we extract the following four conclusions for the perovskites studied in the present paper: for a given cation at the B site, (I) perovskites with cations of identical oxidation state at the A site possess close formation energies; and (II) perovskites with cations of different oxidation states at the A site usually have quite different but ordered formation energies. On the other hand, for a given A-site cation, (III) the formation energies of perovskites vary linearly with respect to the atomic number of the elements at the B site within the same period of the periodic table, and the slopes depend systematically on the oxidation state of the A-site cation; and (IV) the trends in formation energies of perovskites with elements from different periods at the B site depend on the oxidation state of A-site cations. Since the energetics of perovskites is shown to be the superposition of the individual contributions of their constituent oxides, the trends can be rationalized in terms of A–O and B–O interactions in the ionic crystal. These findings reveal the existence of general systematic trends in the formation energies of perovskites and provide further insight into the role of ion–ion interactions in the properties of ternary compounds.

The mechanisms governing the sulfur poisoning of the triple phase boundary (TPB) of Ni-XSZ (X2O3 stabilized zirconia) anodes have been investigated using density functional theory. The calculated sulfur adsorption energies reveal a clear correlation between the size of the cation dopant X(3+) and the sulfur tolerance of the Ni-XSZ anode; the smaller the ionic radius, the higher the sulfur tolerance. The mechanistic study shows that the size of X(3+) strongly influences XSZ's surface energy, which in turn determines the adhesion of Ni to XSZ. The Ni-XSZ interaction has a direct impact on the Ni-S interaction and on the relative stability of reconstructed and pristine Ni(100) facets at the TPB. Together, these two effects control the sulfur adsorption on the Ni atoms at the TPB. The established relationships explain experimentally observed dopant-dependent anode performances and provide a blueprint for the future search for and preparation of highly sulfur tolerant anodes.

Spin-polarized first-principles density-functional electronic structure calculations were performed for 73-atoms embedded clusters representing antiferromagnetic RENi 2 B 2 C (RE = Pr, Nd, Sm, Gd, Ho, Tm). A substantial difference in the extent of the exchange polarization of the conduction electrons between early and late rare-earth compounds is revealed due to the reduced coupling between RE 4f and 5d electrons with increasing Z. This result is relevant to observed phenomena of coexistence of superconductivity and magnetism in these compounds.

The substitution of Ni by the transition metals Fe, Co, and Ru in YNi{sub 2}B{sub 2}C is analyzed using the self-consistent local-density embedded-cluster approach. Changes of partial densities of states, charge density, and bond order are examined to elucidate bonding structure and the interplay between covalent, ionic, and metallic interactions in these highly anisotropic superconductors. Impurity induced modifications in distribution and composition of states near the Fermi level are discussed in terms of the observed drop in {ital T}{sub {ital c}} with impurity concentration. Electric-field gradients are obtained at the central site. In the case of iron substitution with concentration {ital x}{le}0.1, electric quadrupole splitting is compared with M{umlt o}ssbauer experimental results. {copyright} {ital 1996 The American Physical Society.}

Advances in the theoretical understanding of interfacial electrochemistry have, over the past decade, permitted the extension of periodic Density Functional Theory studies, which have traditionally been applied to probe chemistry at gas/solid interfaces, to electrochemical systems where potential-dependent structural and chemical phase transformations occur at liquid/solid interfaces. Indeed, such techniques have been employed to study a surprisingly wide class of electrochemical processes, ranging from electrocatalysis to corrosion. In this talk, we will discuss how these strategies can be applied to predict the detailed, atomic-scale properties of monolayer (oxy)hydroxide base metal films on precious metal and precious metal alloy substrates as a function of applied potential in alkaline solutions. We will describe the analysis of Moire patterns, variable oxidation states, and three-phase boundaries of these films, and we will demonstrate how these results may be used to predict the shape and oxidation states of supported two-dimensional nanoislands as a function of electrochemical conditions. We will close with some perspectives on the possibilities for alkaline electrocatalyst design offered by these systems.

Over the past decade, tremendous advances have made on first principles based modeling of interfacial electrochemistry, which permit not only the mechanistic understanding of the basic thermodynamics and kinetics of complex electrocatalytic reaction networks and but also computational design of new alloy electrocatalysts. [1] Nevertheless, it is still a big challenge for the modeling of electrified interfaces with explicit double layer features (i.e. hydrogen bonds, solvent, electrode potential), which in some instances, yield completely unexpected physical and catalytic properties. For alkaline electrocatalysis at bi-functional three-phase boundaries of ultra-thin 3d transition metal (hydroxy)oxide films, Pt substrates, and the surrounding water,[2,3] it is more challenging, as the interface structures are largely unknown and the large errors in standard DFT calculations on the description of strongly-correlated (hydroxy)oxides. These have significantly impeded the design of new bi-functional catalysts with further improved performance. In this talk, I will briefly review the methodologies we have recently developed, including a synergistic strategy towards highly accurate prediction of Pourbaix diagram of transition metal (hydroxy)oxides,[4] a simple scheme for fast screening of stable single layer transition metal (hydroxy)oxide film/metal interfaces under electrochemical conditions. Next, using hydrogen evolution reaction as an example, I will demonstrate how these techniques can be applied to understand the steady state, the active phases and the catalytic mechanism of mono- and bi-functional catalysts. Finally, I will show these understandings can be used to design new bi-functional catalysts with improved performances. If time permit, I will introduce some of our recent developments on explicitly modeling of electrified electrode/electrode interfaces with full double layer features. [1] J. Greeley, I. E. L. Stephens, A. S. Bondarenko, T. P. Johansson, H. A. Hansen, T. F. Jaramillo, J. Rossmeisl, I. Chorkendorff, J. K. Nørskov, Nat. Chem. 2009, 1, 552-556. [2] Subbaraman, R.; Stamenkovic, V.; Markovic, N. et al, Science 2011, 334, 1256. [3] Subbaraman, R.; Greeley, J.; Stamenkovic, V.; Markovic, N. et al, Nat Mater 2012, 11, 550 [4] Z. Zeng, M. K. Y. Chan, Z.-J. Zhao, J. Kubal, D. Fan, J. Greeley, J. Phys. Chem. C 2015, 119, 18177

WOS: 000298713600054, PubMed ID: 22070406, Many interesting structures have been observed for O(2)-exposed Pt(110). These structures, along with their stability and reactivity toward CO, provide insights into catalytic processes on open Pt surfaces, which have similarities to Pt nanoparticle catalysts. In this study, we present results from ambient-pressure X-ray photoelectron spectroscopy, high-pressure scanning tunneling microscopy, and density functional theory calculations. At low oxygen pressure, only chemisorbed oxygen is observed on the Pt(110) surface. At higher pressure (0.5 Torr of O(2)), nanometer-sized islands of multilayered alpha-PtO(2)-like surface oxide form along with chemisorbed oxygen. Both chemisorbed oxygen and the surface oxide are removed in the presence of CO, and the rate of disappearance of the surface oxide is dose to that of the chemisorbed oxygen at 270 K. The spectroscopic features of the surface oxide are similar to the oxide observed on Pt nanoparticles of a similar size, which provides us an extra incentive to revisit some single-crystal model catalyst surfaces under elevated pressure using in situ tools., Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy [DE-AC02-05CH11231]; National Science Foundation of China [20873142, 20923001]; Ministry of Science and Technology of China [2007CB815205]; Korea Research Foundation (KRF); Korean government (MEST) [2009-0068720]; ALS, The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231. We thank Dr. Yimin Li for the fruitful discussion. W.-X.L. acknowledges financial support by the National Science Foundation of China (Nos. 20873142 and 20923001), the Ministry of Science and Technology of China (No. 2007CB815205). B.S.M. appreciates the support of the Korea Research Foundation (KRF) grant funded by the Korean government (MEST) (No. 2009-0068720). M.E.G. acknowledges the support of the ALS Postdoctoral Fellowship program.

The origin of the unique geometry for nitric oxide (NO) adsorption on Pd(111) and Pt(111) surfaces as well as the effect of temperature were studied by density functional theory calculations and ab initio molecular dynamics at finite temperature. We found that at low coverage, the adsorption geometry is determined by electronic interactions, depending sensitively on the adsorption sites and coverages, and the effect of temperature on geometries is significant. At coverage of 0.25 monolayer (ML), adsorbed NO at hollow sites prefer an upright configuration, while NO adsorbed at top sites prefer a tilting configuration. With increase in the coverage up to 0.50 ML, the enhanced steric repulsion lead to the tilting of hollow NO. We found that the tilting was enhanced by the thermal effects. At coverage of 0.75 ML with $p(2\ifmmode\times\else\texttimes\fi{}2)\text{\ensuremath{-}}3\text{NO}(\text{fcc}+\text{hcp}+\text{top})$ structure, we found that there was no preferential orientation for tilted top NO. The interplay of the orbital hybridization, thermal effects, steric repulsion, and their effects on the adsorption geometries were highlighted at the end.

The capacity of ${\text{Li}}_{2}{\text{C}}_{2}{\text{H}}_{4}^{+}$ and ${\text{TiC}}_{5}{\text{H}}_{5}^{+}$ as hydrogen storage media is studied using first-principles density-functional theory. The present results indicate that these complexes not only enhance the metal bond strength but also increase the number of nondissociative hydrogen molecules attached. The adsorption capacity of ${\text{Li}}_{2}{\text{C}}_{2}{\text{H}}_{4}^{+}(27.5\text{ }\text{wt}\text{ }%)$ is doubled compared with that of ${\text{Li}}_{2}{\text{C}}_{2}{\text{H}}_{4}$. The enhanced electrostatic field around the Li atom originating from the increased charge transfers from Li to ${\text{C}}_{2}{\text{H}}_{4}^{+}$ accounts for the high capacity. For ${\text{TiC}}_{5}{\text{H}}_{5}^{+}$, the first ${\text{H}}_{2}$ is adsorbed in molecular form, while it is adsorbed dissociatively on the ${\text{TiC}}_{5}{\text{H}}_{5}$ complex. This is due to the favorable overlap of the highest occupied molecular orbital of Ti and the lowest unoccupied molecular orbital of ${\text{H}}_{2}$. Furthermore, the number of adsorbed ${\text{H}}_{2}$ on ${\text{TiC}}_{5}{\text{H}}_{5}$ is limited to only four, whereas the number increases to five on ${\text{TiC}}_{5}{\text{H}}_{5}^{+}$. The availability of the ${d}_{{z}^{2}}$ orbital of Ti in ${\text{TiC}}_{5}{\text{H}}_{5}^{+}$ has been found to be responsible for the fifth ${\text{H}}_{2}$ adsorption with a hydrogen uptake of $8.1\text{ }\text{wt}\text{ }%$. It is demonstrated that controlling the charge state of the metal-organic molecules may play a significant role in the search for hydrogen storage media.

In this work, we report a first-principles investigation of the energetics, structures, electronic properties, and core-level shifts of NO adsorption on the Pt(111) surface. Our calculations are based on density functional theory within the framework of the ultrasoft pseudopotential plane-wave and the all-electron projected augmented-wave methods. We found that at 0.25, 0.50, and 0.75 monolayer, NO adsorbs preferentially in the fcc, $\text{fcc}+\text{top}$, and $\text{fcc}+\text{top}+\text{hcp}$ sites, respectively. The geometric parameters, adsorption energies, vibrational frequencies, and work-function changes are in good agreement with the experimental data. The interaction between NO and Pt(111) was found to follow a donation--back-donation process, in which the NO $\ensuremath{\sigma}$ states donate electrons to the substrate $\text{Pt}\text{ }d$ states, while the substrate $\text{Pt}\text{ }d$ states back donate to the NO $\ensuremath{\pi}$ states. Though there is an overall net charge transfer from the substrate to the NO adsorbate regardless of the adsorption sites and coverages, the spatial redistribution of the transferred electron is site dependent. The charge accumulation for NO in the top sites occurs closer to the surface than NO in the hollow sites, which results in the reduction of the Pt(111) surface work function for the top NO but an increase for the hollow NO. The core-level shifts of the topmost surface Pt atoms coordinated with top and hollow NO molecules at different coverages are in excellent agreement with experiments. In contrast, the N $1s$ core-level shifts between top and hollow NO $(\ensuremath{\sim}0.7\text{ }\text{eV})$ deviated significantly from the zero shift found in experiments. Our analysis indicates that the difference may come from the thermal vibration and rotation of adsorbed NO on the Pt(111) surface.

We present a detailed theoretical study of the electronic transport properties of monolayer graphene. The quantum and transport conductivities are calculated on the basis of the usual momentum-balance equation derived from a semiclassical Boltzmann equation. We investigate carrier-impurity scattering in a massless Dirac quasiparticle system. The carrier interactions with remote and background impurities are considered, and the carrier–carrier screening is included within the random phase approximation. The dependence of the conductivities on temperature is also examined. Moreover, a very simple analytical formula is proposed such that only one fitting parameter is needed in order to make a quantitative comparison with the experimental results.

In the present study, on the basis of detailed density functional theory (DFT) calculations, and using Ni hydroxy(oxide) films on Pt(111) and Au(111) electrodes as model systems, we describe a detailed structural and electrocatalytic analysis of hydrogen evolution (HER) at three-phase boundaries under alkaline electrochemical conditions. We demonstrate that the structure and oxidation state of the films can be systematically tuned by changing the applied electrode potential and/or the nature of substrates. Structural features determined from the theoretical calculations provide a wealth of information that is inaccessible by purely experimental means, and these structures, in turn, strongly suggest that a bifunctional reaction mechanism for alkaline HER will be operative at the interface between the films, the metal substrates, and the surrounding aqueous medium. This bifunctionality produces important changes in the calculated barriers of key elementary reaction steps, including water activation and dissociation, as compared to traditional monofunctional Pt surfaces. The successful identification of the structures of thin metal films and three-phase boundary catalysts is not only an important step towards accurate identification and prediction of a variety of oxide/electrode interfacial structure-properties relationships, but also provides the foundation for rational design and control of ‘targeted active phases’ at catalytic interfaces. The successful design of bifunctional electrocatalysts that exploit these structures, in turn, could ultimately lead to advances in the development of alkaline fuel cells. References 1Surnev, S.; Fortunelli, A.; Netzer, F. P. Chem Rev 2012, 113, 4314. 2Shaikhutdinov, S.; Freund, H.-J. Annu. Rev. Phys. Chem. 2012, 63, 619. 3Subbaraman, R.; Stamenkovic, V.; Markovic, N. et al, Science 2011, 334, 1256. 4Subbaraman, R.; Greeley, J.; Stamenkovic, V.; Markovic, N. et al, Nat Mater 2012, 11, 550 5Strmcnik, D; Stamenkovic, V. R.; Markovic, N. et al, Nat Chem 2013, 5, 300.

With increased energy demands, fuel cells offer a viable solution due to their efficient conversion of energy from various fuels. Switching to a basic electrolyte, many metals that would be susceptible to corrosion in an acidic environment become stable in an alkaline one. This allows for the inclusion of non-precious metals in the electrodes. However, the kinetics in an alkaline environment tend to be sluggish; this must be overcome for alkaline fuel cells to become commercially realizable. While many model electrodes have been investigated for possibility to improve the kinetics in alkaline fuel cells, this work focuses on thin film electrodes and reactions happening at the interphase between the substrate and the film. The introduction of three-phase boundaries can allow the various reaction intermediates to preferentially bind to different locations, thus possibly allowing one to break away from scaling relationships. This could ideally enable the catalyst to reach higher catalytic activity [1]. To determine the effectiveness of these electrodes, density functional theory (DFT) is employed. Before work was done to model the interphases, extensive work was done examining various moiré patterns for various oxidation states of transition metal films, with a focus on FeOxHy films. In this work, the stability of a variety of transition metal (hydr)oxide thin films on Pt and Au are first examined for stability for their future prospects of viable catalysts for fuel cell applications. In addition, phase diagrams are constructed to determine the state of the film at a given voltage, something crucial for designing optimal catalysts. A DFT + U scheme is employed to model the thin films, where U values are fitted by correcting the formation energies. While the oxidation state and strain of the film are predicted from the full film phase diagrams, the nature of the interphase needed to be determined. The focus , hydrogen evolution and CO oxidation at these interphases with each reaction occurring at a different equilibrium potentials. This knowledge necessitated the creation of phase diagrams for the interfaces, to identify the most stable oxidation state the edge may take. With these phase diagrams, the thermodynamics and kinetics for the two reactions could be calculated with DFT along with nudged elastic band (NEB) calculations to calculate the activation barriers. These results are then compared with those on a clean Pt surface. [1] R. Subbaraman, D. Tripkovic, K. Chang, D. Strmcnik, A. P. Paulikas, P. Hirunsit, M. Chan, J. Greeley, V. Stamenkovic, N. M. Markovic. Nature Materials. 11, 550 (2012)

We studied the influence of controlled surface-limited oxidation of electrodeposited epitaxial Co(0001)/Au(111) films on their magnetic anisotropy energy using real time in situ magneto optical Kerr effect and density functional theory (DFT) calculations. We investigated the Co first electrochemical oxidation step which we demonstrate to be completely reversible and determined the structure of this oxide layer. We show that the interface magnetic anisotropy of the Co film increases by 0.36 erg/cm2 upon Co surface oxidation. We performed DFT calculations to determine the different surface structures in a wide potential range as well as the charge transfer at the Co surface. Our results suggest that the magnetic anisotropy change is correlated with a positive charge increase of 0.54 e− for the Co surface atom upon oxidation.

The anisotropic polarized spin injection effect on the critical current density Jc of La0.7Sr0.3MnO3/La1.85Sr0.15CuO4 heterostructure is systematically investigated. It is found that the contribution of δTc pinning mechanism is enhanced with spin injection. The angle dependent Jc(θ) near H//c can be scaled by the Ginzburg-Landau (G-L) expression, while for H//ab the intrinsic pinning drives the data to deviate from the G-L fitting. The relative changes of Jc affected by spin injection show opposite variation trends with increasing fields for H//ab and H//c, which is probably related to the different suppressions of injected spins on different flux pinnings.

Electronic structures and states of ${\mathrm{Na}}_{x}{\mathrm{CoO}}_{2}$ $(x=0,$ 0.35, 0.5, and 0.75) with the same lattice parameters as superconducting ${\mathrm{Na}}_{x}{\mathrm{CoO}}_{2}\ensuremath{\cdot}m{\mathrm{H}}_{2}\mathrm{O}$ have been studied by utilizing the full-potential linear muffin-tin orbital methods, from which some electronic interaction parameters are obtained. Most of the carriers in doped compounds have ${a}_{1g}$ character. The effective on-site Coulomb interaction ${U}_{\mathrm{dd}}=4\mathrm{eV}$ for $x=0;$ the $\mathrm{pd}$ hybridizations ${t}_{\mathrm{pd}}^{\ensuremath{\sigma}}$ and ${t}_{\mathrm{pd}}^{\ensuremath{\pi}}$ are $\ensuremath{-}1.40$ and 0.70 eV, respectively; the density of states at ${E}_{F}$ for $x=0.35$ is about 1.0 states/eV in the local-density approximation $(\mathrm{LDA})+U$ scheme, much smaller than 6\char21{}7 states/eV in the LDA scheme. The role of the electronic correlation on the superconductivity in ${\mathrm{Na}}_{0.35}{\mathrm{CoO}}_{2}\ensuremath{\cdot}m{\mathrm{H}}_{2}\mathrm{O}$ is discussed.

Al2O3/GeOx/Ge gate stack fabricated by an in situ cycling ozone oxidation (COO) method in the atomic layer deposition (ALD) system at low temperature is systematically investigated. Excellent electrical characteristics such as minimum interface trap density as low as 1.9 × 1011 cm−2 eV−1 have been obtained by COO treatment. The impact of COO treatment against the band alignment of Al2O3 with respect to Ge is studied by x-ray photoelectron spectroscopy (XPS) and spectroscopic ellipsometry (SE). Based on both XPS and SE studies, the origin of gate leakage in the ALD-Al2O3 is attributed to the sub-gap states, which may be correlated to the OH-related groups in Al2O3 network. It is demonstrated that the COO method is effective in repairing the OH-related defects in high-k dielectrics as well as forming superior high-k/Ge interface for high performance Ge MOS devices.