Grand Canonical Adaptive Resolution Simulation for Molecules with Electrons: A Theoretical Framework based on Physical Consistency

A theoretical scheme for the treatment of an open molecular system with electrons and nuclei is proposed. The idea is based on the Grand Canonical description of a quantum region embedded in a classical reservoir of molecules. Electronic properties of the quantum region are calculated at constant electronic chemical potential equal to that of the corresponding (large) bulk system treated at full quantum level. Instead, the exchange of molecules between the quantum region and the classical environment occurs at the chemical potential of the macroscopic thermodynamic conditions. T he Grand Canonical Adaptive Resolution Scheme is proposed for the treatment of the classical environment; such an approach can treat the exchange of molecules according to first principles of statistical mechanics and thermodynamic. The overall scheme is build on the basis of physical consistency, with the corresponding definition of numerical criteria of control of the approximations implied by the coupling. Given the wide range of expertise required, this work has the intention of providing guiding principles for the construction of a well founded computational protocol for actual multiscale simulations from the electronic to the mesoscopic scale.Comment: Computer Physics Communications (2017), in pres

Sulfated ZrO 2 supported CoMo sulfide catalyst by surface exsolution for enhanced hydrodeoxygenation of lignin-derived ethers to aromatics

Abstract(#br)Catalytic transformation of lignin is a sustainable way to provide aromatics, which depends on the structure and property of catalytic sites. A bifunctional sulfated ZrO 2 supported CoMo sulfide catalyst has been synthesized by in situ exsolution approach. The exsolved CoMo-sZr(exs) catalyst significantly enhanced the initial C–O bond cleavage rate (0.058 mol·g −1 ·h −1 ) compared to the impregnated and physically mixed sulfated ZrO 2 supported CoMo sulfide catalysts. Notably, the reusability tests also showed that the as-prepared catalyst presented total ethers conversion of 94% with aromatics yield of 86% after four consecutive cycles. This was related to the appropriate sulfide-support interaction, acid sites and highly-dispersed CoMo sulfide, in conformity with the catalyst characterization. Thereby it could facilitate reactant adsorption and effectively break down the C–O bonds in lignin derived fragments to form aromatics. This work points out a new avenue for the design of effective bifunctional catalysts for lignin depolymerization

Study on the Effect of Pre-Refinement and Heat Treatment on the Microstructure and Properties of Hypoeutectic Al-Si-Mg Alloy

Hypoeutectic Al-Si-Mg alloys with a silicon content of around 10 wt % are widely used in the aerospace and automotive fields due to their excellent casting properties. However, the occurrence of “silicon poisoning” weakens the refinement effect of a conventional refiner system such as Al-5Ti-1B. In this paper, we proposed the “pre-refinement” method to avoid the “Si poisoning” to recover the refinement effect of Al-5Ti-1B. The core concept was to adjust the order of adding the Si element to form the TiAl3 before forming the Ti-Si intermetallic compound. To prove the effectiveness of the “pre-refinement” method, three alloys of “pre-refinement”, “post-refinement”, and “non-refinement” of an Al-10Si-0.48Mg alloy were prepared and characterized in as-cast and heat-treatment states. The results showed that the average grain diameter of the “pre-refinement” alloy was 60.19% smaller than that of the “post-refinement” one and 81.34% smaller than that of the “non-refinement” one, which demonstrated that the proposed method could effectively avoid the “silicon poisoning” effect. Based on a refined grain size, the “pre-refinement” Al-10Si-0.48Mg alloy showed the best optimization effect in mechanical properties after a solid-solution and subsequent aging heat treatments. The best mechanical properties were found in the “pre-refinement” alloy with 2 h of solid solution treatment and 10 h of aging treatment: a hardness of 92 HV, a tensile strength of 212 MPa, and an elongation of 20%

Direct Synthesis of Thermoplastic Polyolefin Elastomers from Nickel-Catalyzed Ethylene Polymerization

As a promising alternative to thermoset elastomers, thermoplastic elastomers (TPEs) have attracted much attention because of their unique properties, including processability, reusability and recyclability. The synthesis of TPEs based on olefinic building blocks usually requires the use of long chain α-olefins, multiple steps, and/or multiple catalysts. The concept of using only ethylene as feedstock in a single step is fascinating but also very challenging. In this contribution, we report the synthesis of polyethylene-based TPEs through α-diimine nickel-catalyzed ethylene polymerization. The stress-at-break and strain-at-break values of these polyethylene products could be tuned over a very wide range using different nickel catalysts and different polymerization conditions. Most importantly, products with excellent elastic properties could be generated in the screening process

Covalent Attachment of a Rhenium Bipyridyl CO 2 Reduction Catalyst to Rutile TiO 2

We have characterized the covalent binding of the CO2 reduction electrocatalyst ReC0A (Re(CO)3Cl(dcbpy) (dcbpy =4,4′-dicarboxy-2,2′-bipyridine)) to the TiO2 rutile (001) surface. The analysis based on sum frequency generation (SFG) spectroscopy and density functional theory (DFT) calculations indicates that ReC0A binds to TiO2 through the carboxylate groups in bidentate or tridentate linkage motifs. The adsorbed complex has the dcbpy moiety nearly perpendicular to the TiO2 surface and the Re exposed to the solution in a configuration suitable for catalysis