Hydrogenation of 3d-metal oxide clusters: Effects on the structure and magnetic properties

The geometrical structures and properties of the M₈O₁₂, M₈O₁₂H₈, and M₈O₁₂H₁₂ clusters are explored using density functional theory with the generalized gradient approximation for all 3d-metals M from Sc to Zn. It is found that the geometries and total spin magnetic moments of the clusters depended strongly on the 3d-atom type and the hydrogenation extent. More than the half of all of the 30 clusters had singlet lowest total energy states, which could be described as either nonmagnetic or antiferromagnetic. Hydrogenation increases the total spin magnetic moments of the M₈O₁₂H₁₂ clusters when MMn Ni, which become larger by four Bohr magneton than those of the corresponding unary clusters M₈. Hydrogenation substantially affects such properties as polarizability, forbidden band gaps, and dipole moments. Collective superexchange where the local total spin magnetic moments of two atom squads are coupled antiparallel was observed in antiferromagnetic singlet states of Fe₈O₁₂H₈ and Co₈O₁₂H₈, whereas the lowest total energy states of their neighbors Mn₈O₁₂H₈ and Ni₈O₁₂H₈ are ferrimagnetic and ferromagnetic, respectively. Hydrogenation leads to a decrease in the average binding energy per atom when moving across the 3d-metal atom series. © 2018 Wiley Periodicals, Inc.     

Extension of the Method of Moments in Nonlinear Free Radical Polymerization

The method of moments is a simple, efficient method simulating polymerization processes. Its use is said to be limited in nonlinear free radical polymerizations with branching or crosslinking due to the assumptions needed. Here, moment equations are derived without assuming steady state, one radical per molecule, or a statistical distribution of connections. Equations are valid up to the gel point. The bulk solution is formally identical to the pseudo kinetic approach by Tobita and Hamielec if moments of dead polymer are replaced by the sum of dead and life polymers. The method relies on analytical solutions of the moments of the molecular weight distributions (MWD) of instantaneous primary chains. In emulsion polymerization compartmentalization of radicals complicates the calculation. An alternative approximation of these MWDs is presented. The present extension allows nonlinear free radical polymerization to be readily included in the computer based design and optimization of polymerization processes and to check more detailed calculations of the MWD.

     

Diabatic investigation for the NaRb molecule

An extensive diabatic investigation of the NaRb species has been carried out for all excited states up to the ionic limit Na^‐Rb⁺. An ab initio calculation founded on the pseudopotential, core polarization potential operators and full configuration interaction has been used with an efficient diabatization method involving a combination of variational effective hamiltonian theory and an effective overlap matrix. Diabatic potential energy curves and electric dipole moments (permanent and transition) for all the symmetries Σ⁺, Π, and Δ have been studied for the first time. Thanks to a unitary rotation matrix, the examination of the diabatic permanent dipole moment (PDM) has shown the ionic feature clearly seen in the diabatic ¹Σ⁺ potential curves and confirming the high imprint of the Na^‐Rb⁺ ionic state in the adiabatic representation. Diabatic transition dipole moments have also been computed. Real crossings have been shown for the diabatic PDM, locating the avoided crossings between the corresponding adiabatic energy curves.     

用矩量法解阻尼介质中简支方板的塑性动力响应问题

本文用矩量法解薄板塑性动力响应问题，分析阻尼介质对简支方板塑性动力响应的影响，对计算结果进行了讨论．     

PSEUDOHALOGEN CHEMISTRY. PART IV. HETEROLYTIC ADDITION OF THIOCYANOGEN TO ALKENES

Abstract

Thiocyanogen reacts slowly with alkenes, in the presence of a radical inhibitor in benzene or acetic acid in the dark at 25°, to yield α,β-dithiocyanates, α-isothiocyanates-β-thiocyanates and, in acetic acid, α-acetoxy-β-thiocyanates in varying proportions. The additions to alkyl alkenes are trans-stereospecific, and, in the case of the α-isothiocyanato-β-thiocyanates, non-regiospecific. The additions to aryl alkenes are trans-stereoselective and regiospecific, yielding the Markownikov-orientated α-isothiocyanato-β-thiocyanates. A heterolytic mechanism involving a two-step, kinetically controlled addition, with the formation of a cyano-sulfonium ion intermediate, e.g., 35, in the case of alkyl alkenes and an open carbonium ion, e.g., 36, in the case of aryl alkenes, is suggested. The diothiocyanate: isothiocyanato-thiocyanate ratios are discussed in terms of kinetic and steric control of reaction.     

Birnbaum‐Saunders distribution: A review of models,analysis, and applications

Birnbaum and Saunders introduced a two‐parameter lifetime distribution to model the fatigue life of a metal, subject to cyclic stress. Since then, extensive work has been done on this model providing different interpretations, constructions, generalizations, inferential methods, and extensions to bivariate, multivariate, and matrix‐variate cases. More than 200 papers and one research monograph have already appeared describing all these aspects and developments. In this paper, we provide a detailed review of all these developments and, at the same time, indicate several open problems that could be considered for further research.     

考虑塑性变形发展程度系数的RC梁开裂弯矩改进计算公式

针对RC梁开裂荷载计算方法尚未统一的现状，首先，结合18根RC梁试验数据对比了已有的6种RC梁开裂弯矩计算公式，发现开裂弯矩理论计算值与试验值的偏差大小和混凝土强度有关；然后，通过提出塑性变形发展程度系数k，推导新的RC梁开裂弯矩计算公式，并进一步基于k值和塑性影响系数计算值γ_k进行改进；最后，选取12根RC试验梁验证改进公式的准确性，证明改进公式的计算值与试验值吻合更好且偏于安全。     

Manipulation of inherent characteristics of graphene through N and Mg atom co-doping; a DFT study

First-principles calculations were performed to investigate the structural, electronic, magnetic and optical properties of nitrogen (N) and magnesium (Mg) atom co-doped graphene systems. We observed that, N and Mg atom co-doping in graphene, introduces half-metallic properties in the electronic structure of graphene, introduces ferromagnetism behavior along with new trends in optical properties of graphene. Doping site and concentration of N and Mg atoms in graphene was changed and resulting effects of these changes on aforementioned properties were investigated. Through density of states plots we observed that, Mg atom sp orbitals mainly induced magnetic moments in graphene. It was revealed that, N/Mg atoms substitution in graphene introduces a red shift in absorption spectrum towards visible range and a finite absorption coefficient quantity value in 0 to 3 eV and 7 to 11 eV energy intervals is also produced, that is unavailable for absorption spectrum of intrinsic graphene. Moreover, N/Mg atoms co-doping produces increment in the reflectivity parameter of graphene in low lying energy region, while producing diminishing behavior in the higher energy range. These results offer a possibility to tune electronic, magnetic and optical characteristics of graphene sufficiently for utilization in graphene based spintronic and optoelectronic devices.     

Gravitational Waves,baryon asymmetry of the universe and electric dipole moment in the CP-violating NMSSM

In this work, we make the first study of electroweak baryogenesis(EWBG) based on the LHC data in the CP-violating next-to-minimal supersymmetric model(NMSSM) where a strongly first order electroweak phase transition(EWPT) is obtained in the general complex Higgs potential. With representative benchmark points which pass the current LEP and LHC constraints, we demonstrate the structure of EWPT for those points and how a strongly first order EWPT is obtained in the complex NMSSM where the resulting gravitational wave production properties are found to be within the reaches of future space-based interferometers like BBO and Ultimate-DECIGO. We further calculate the generated baryon asymmetries where the CP violating sources are(1): higgsino-singlino dominated,(2): higgsino-gaugino dominated or(3): from both sources. It is shown that all three representing scenarios could evade the strong constraints set by various electric dipole moments(EDM) searches where cancellations among the EDM contributions occur at the tree level(higgsino-singlino dominated) or loop level(higgsino-gaugino dominated).The 125 GeV SM like Higgs can be either the second lightest neutral Higgs H_2 or the third lightest neutral Higgs H_3. Finally, we comment on the future direct and indirect probe of CPV in the Higgs sector from the collider and EDM experiments.