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Molecular dynamics simulations are used to investigate the effects of temperature, strain rate and molecule length on the deformation of graphene/polyethylene composites. At higher temperature, the host molecules move easily to fit the strain during the deformation. When the strain rate is lower, atoms in the composite model are more relaxed to fit the strain, thus the yield stress of the composite model is smaller than that at a higher strain rate. Due to the longer the length of molecules, the relative movement between molecules is more difficult with the increase of the strain, resulting in a larger yield stress.

Iron sulfides have emerged as a fascinating class of materials in electromagnetics and catalysis areas, which however are challenging in first-principles modeling because of the strongly-correlated interactions between Fe 3d and S 3p electrons. Here, we assess the performances of 14 density functionals on the structural, electronic, and magnetic properties of five iron sulfides. The PBE + U with Ueff = 2.0 eV has the overall best performance. After evaluating functionals and obtaining reliable properties, our final goal is from predicting to correlating in order to do high throughput screening for the systems since the complex structures and phases of iron sulfides, to put it in another way, to hunting a reliable descriptor for predicting their properties. In the work, we demonstrate that the crystal orbital Hamilton population (COHP) and Bader charge of Fe atoms presents a good correlation with the empirical bond valence. Our results open a new avenue to effectively investigate phases and properties for various structures of iron sulfides. Indeed, the correlations between COHP/Bader charge and bond valence can be extended to other systems.

Encapsulating non-precious metals within graphene layers represents a promising strategy to substitute precious metal catalyst towards the oxygen evolution reaction (OER). The surface electronic structure of graphene can significantly affect the OER performance, which depends on the types of encapsulated metal and their proportion but it still lacks efficient methods to modulate them. Herein, we report a universal strategy to encapsulate FeNi binary metal nanoalloy within ultrathin graphene layers, which can efficiently optimize the electronic properties and the OER activity on the graphene surface via modulating Fe/Ni ratio. The optimized catalyst with Fe/Ni of 1 shows a low overpotential of 280 mV at the current density of 10 mA cm−2. Both the catalytic activity and durability of the catalyst are better than the commercial IrO2. Theoretical calculations indicate that the adsorption strength of each intermediate on graphene can be optimally balanced by modulating the metal proportion of the encapsulated FeNi, leading to an enhanced OER activity with reduced overpotential on the graphene surface.

Constructing and understanding the doping effect of secondary metal in transition metal carbide (TMC) catalysts is pivotal for the design of low-cost hydrogen evolution reaction (HER) electrocatalysts. In this work, we developed a wet-chemistry strategy for synthesizing Co-modified Fe5C2 nanoparticles ((Fe1−xCox)5C2 NPs) as highly active HER electrocatalysts in basic solution. The structure of (Fe1−xCox)5C2 NPs was characterized by X-ray diffraction (XRD), extended X-ray absorption fine structure spectra (EXAFS) and scanning/transmission electron microscopy (S/TEM), indicating that the isomorphous substitution of cobalt in the lattice of Fe5C2. (Fe0.75Co0.25)5C2 exhibited the best HER activity (174 mV for j = −10 mA/cm2). Computational calculation results indicate that Co provides the most active site for HER. X-ray adsorption spectra (XAS) studies further suggested that the electron transfer in Fe-C bonds are enhanced by the substitution of Co, which modulates the hydrogen adsorption on the adjacent electronic-enriched carbon, and therefore promotes HER activity. Our results affirm the design of low-cost bimetallic TMCs based HER catalysts.

CO2-based stereocomplexed polycarbonates derived from the intermolecularly interlocked interaction between the enantiopure polymers with the opposite configuration exhibit high crystallinity, excellent thermal and mechanical stabilities. Deep insights into the mechanism of stereocomplexation are of particular importance to the design and manufacture of new promising and sustainable polycarbonates with enhanced physicochemical properties. Our solid-state NMR experiments linking with DFT computations clearly reveal the specific chain–chain interactions in a typical stereocomplexed poly (4,4-dimethyl-3,5,8-trioxabicyclo[5.1.0] octane carbonate) (PCXC). 13C CP/MAS NMR, 1H DUMBO MAS NMR and 13C/1H relaxation-time measurements indicate that the formation of stereocomplex reduces the local mobilities of carbonyl, methine and methylene groups in each chain of PCXC significantly. Through a combination of two-dimensional 1H 13C HETCOR NMR and DFT calculation analysis, the cis-/trans- conformations and packing models of PCXC chains in the amorphous, enantionpure isotactic and stereocomplexed polycarbonates are identified. The splitting of 13C and 1H NMR chemical shifts of methine groups in the backbone carbon region demonstrates the ordered interlock interactions between the R- and S- chain in the stereocomplexed PCXC.

We systematically investigate the structural, electronic and magnetic properties, bonding analysis, as well as surface morphology of transition metal monoxides (FeO, CoO and NiO) utilizing density functional theory (DFT) with various functionals across from GGA to GGA+U and hybrid functional. Our results reveal that the screened hybrid functional (HSE) could give a reasonable description on structural and electronic properties of these strongly correlated systems when compared to experiments. Local approximation GGA functional fails to yield the accuracy band gaps. GGA+U approximation are rational when given a reasonable U, but the U which reproduce a reasonable band gap often yield a significant error in describing other properties such as lattice constant or magnetic moment. The computed Crystal Orbital Overlap Population (COOP) indicates that cubic FeO and CoO are metastable phase, while the distortion occurs to enhance stability. Based on the reliable functional, the surface morphology of FeO, CoO and NiO are predicted using Wulff construction approach.

The ZSM-5 zeolite with an unusual snowflake-shaped morphology was hydrothermally synthesized for the first time, and compared with common ellipsoidal and boat-like shaped samples. These samples were characterized by N 2 adsorption-desorption, X-ray fluorescence spectroscopy, scanning electron microscopy, X-ray diffraction, magic angle spinning nuclear magnetic resonance, temperature-programmed desorption of ammonia, and infrared spectroscopy of pyridine adsorption. The results suggest that the BET surface area and SiO 2 /Al 2 O 3 ratio of these samples are similar, while the snowflake-shaped ZSM-5 zeolite possesses more of the (101) face, and distortion, dislocation, and asymmetry in the framework, resulting in a larger number of acid sites than the conventional samples. Catalysts for the methanol to olefin (MTO) reaction were prepared by loading Ca on the samples. The snowflake-shaped Ca/ZSM-5 zeolite exhibited excellent selectivity for total light olefin (72%) and propene (39%) in MTO. The catalytic performance influenced by the morphology can be mainly attributed to the snowflake-shaped ZSM-5 zeolite possessing distortion, dislocation, and asymmetry in the framework, and lower diffusion limitation than the conventional samples.

Radiation-induced soft error has become an emerging reliability threat to high performance microprocessor design. As the size of on chip cache memory steadily increased for the past decades, resilient techniques against soft errors in cache are becoming increasingly important for processor reliability. However, conventional soft error resilient techniques have significantly increased the access latency and energy consumption in cache memory, thereby resulting in undesirable performance and energy efficiency degradation. The emerging 3D integration technology provides an attractive advantage, as the 3D microarchitecture exhibits heterogeneous soft error resilient characteristics due to the shielding effect of die stacking. Moreover, the 3D shielding effect can offer several inner dies that are inherently invulnerable to soft error, as they are implicitly protected by the outer dies. To exploit the invulnerability benefit, we propose a soft error resilient 3D cache architecture, in which data blocks on the soft error invulnerable dies have no protection against soft error, therefore, access to the data block on the soft error invulnerable die incurs a considerably reduced access latency and energy. Furthermore, we propose to maximize the access on the soft error invulnerable dies by dynamically moving data blocks among different dies, thereby achieving further performance and energy efficiency improvement. Simulation results show that the proposed 3D cache architecture can reduce the power consumption by up to 65% for the L1 instruction cache, 60% for the L1 data cache and 20% for the L2 cache, respectively. In general, the overall IPC performance can be improved by 5% on average.

The effect of adding aromatic compounds and varying the AlCl 3 molar fraction on the catalytic performance of chloroaluminate ionic liquids in isobutane/2-butene alkylation was investigated. 27 Al NMR results and comparison with alkylation catalyzed by solid AlCl 3 reveal that the activity of the ionic liquids presumably comes from traces of AlCl 3 or Al 2 Cl 6 . The addition of benzene increases the selectivity of C 8 as well as the TMP:DMH ratio in the alkylate. The performance of the modified catalyst is optimized at high isobutane to 2-butene ratios and low temperatures. The used catalyst can be regenerated by replenishment of the aromatic additives.