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Precipitation kinetics of ordered γ′ phase and microstructure evolution in a Ni-Al alloy

MATERIALS CHEMISTRY AND PHYSICS 2016年第0期182卷 125-132页

作者： Wu, Xingchao Li, Yongsheng Huang, Mengqiong Liu, Wei Hou, Zhiyuan Nanjing Univ Sci & Technol Sch Mat Sci & Engn Nanjing 210094 Jiangsu Peoples R China

The precipitation kinetics of ordered gamma' (L1(2)-Ni3Al) phase from nucleation and growth to coarsening in a Ni-Al alloy is studied by phase field simulation. The initial nucleation of the gamma' phase is quantitatively described by the variations of composition and order parameter profiles of the initial Al-enriched cluster, and the coarsening kinetics is clarified with the time exponent of the average particle radius of gamma' phase. The precipitation of the gamma' phase from the supersaturated gamma solid solution goes through the non-stoichiometric ordered phase, stoichiometric ordered phase, growth and coarsening. The time exponent of the average radius of the gamma' phase with coherent equilibrium is smaller than that indicated by the Lifshitz-Slyozov-Wagner theory at the coarsening stage, and it decreases from 1.35 of the nucleation and growth stage to 0.22 of the coarsening stage. The peak of the particle size distribution decreases and the width of the particle size distribution increases as the aging progresses. As the average radius of the gamma' phase increases, the average aspect ratio of the gamma' phase undergoes a slowly increase to a fast increase from nucleation to growth stage, then goes into a relatively stable state at the coarsening stage. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Alloys Annealing computer modelling and simulation Phase transitions

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The effect of group-substitution on structures and photophysical properties of rhenium(I) tricarbonyl complexes with pyridyltetrazole ligand: A DFT/TDDFT study

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MATERIALS CHEMISTRY AND PHYSICS 2016年 178卷 173-181页

作者： Yang, Xiao-Zhu Wang, Ya-Ling Guo, Jing-Ye Zhang, Ting-Ting Jia, Jian-Feng Wu, Hai-Shun Shanxi Normal Univ Key Lab Magnet Mol & Magnet Informat Mat Minist Educ Linfen 041000 Peoples R China Shanxi Normal Univ Sch Chem & Mat Sci Linfen 041000 Peoples R China

A series of rhenium(I) tricarbonyl complexes having a general formula fac-[Re (CO)(3)(L)(R-N boolean AND N)] (L = Br;N boolean AND N = tert-butylated pyridyltetrazole;R = -H, 1;-NO2, 2;-CN, 3;-OCH3, 4;-CH3, 5) have been investigated theoretically by density functional theory (DFT) and time-dependent density functional theory (TDDFT) methods. The calculated results reveal that introductions of different groups on R position of N boolean AND N ligand can induce changes on electronic structures, photophysical properties and emission quantum yield for these complexes. When the electron-withdrawing groups (-NO2 and -CN) are introduced in complex 2 and 3, the lowest energy absorption and emission bands are red-shifted compared with that of 1. On the contrary, the introduction of electron-donating group (-OCH3 and -CH3) in complex 4 and 5 cause corresponding blue-shifted. For these complexes, the stronger electron donating ability of introduced group on N boolean AND N ligand is, the larger blue-shifted of the lowest energy absorption and emission bands is. The solvent effect on absorption and emission spectrum indicates that the lowest-energy absorption and emission bands have both red shifts with the decrease of solvent polarity. The electronic affinity (EA), ionization potential (IP) and reorganization energy (lambda) results show that complex 4 may be suitable to be used as an emitter in organic light-emitting diodes OLEDs. Meanwhile the emission quantum yield of complex 4 is possibly higher than other complexes. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Organometallic compounds Photoemission computer modelling and simulation Electronic structure

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Thermo-kinetic mechanisms for grain boundary structure multiplicity, thermal instability and defect interactions

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MATERIALS CHEMISTRY AND PHYSICS 2016年 179卷 254-265页

作者： Burbery, N. J. Das, R. Ferguson, W. G. Univ Auckland Dept Mech Engn Auckland 1010 New Zealand Univ Auckland Dept Chem & Mat Engn Auckland 1010 New Zealand

Grain boundaries (GBs) provide a source and/or a sink for crystal defects and store elastic energy due to the non-uniform atomic bonding structure of the GB core. GB structures are thermodynamically driven to transition to the lowest energy configuration possible;however to date there has been little evidence to explain why specific GB structures have a low energy state. Furthermore, there is little quantitative demonstration of the significance of physical and GB structure characteristics on the GB energy, thermal stability, and the effect of temporary local GB structure transformations on defect interactions. This paper evaluates the defect interactions and structure stability of multiple Sigma 5(310) GB structures in bi-crystals of pure aluminium, and systematically investigates the features at 0 K to characterise multiple metastable structures. Structure stability is evaluated by utilising unstable vacancy defects to initiate GB transformations, and using nudged elastic band simulations to quantify this with the activation energy. The emission of stable vacancy defects from the 'stable' and metastable grain boundaries is also evaluated in the same mariner. A detailed analysis of dislocation nucleation at the atomistic scale demonstrates that local transformations of GB structure between stable and metastable intermediates can provide a mechanism to accommodate the generation of crystal defects. Kinetic (time-dependent) effects that compete with energetic driving forces for structural transformations of GBs are shown to cause a significant effect on the activation properties that may exceed the influence of GB potential energy. The results demonstrate that GB structural multiplicity can be associated with the generation and absorption of dislocations and vacancies. This paper demonstrates the suitability of atomistic simulations coupled with nudged elastic band simulations to evaluate fundamental thermodynamic properties of pure FCC metals. Overall, this paper de

关键词： Metals Crystal structure Thermodynamic properties computer modelling and simulation Dislocations Interfaces

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Validation and predictions of coupled finite element and cellular automata model: Influence of the degree of deformation on static recrystallization kinetics case study

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MATERIALS CHEMISTRY AND PHYSICS 2016年 179卷 282-294页

作者： Madej, Lukasz Sitko, Mateusz Radwanski, Krzysztof Kuziak, Roman AGH Univ Sci & Technol Al Mickiewicza 30 PL-30059 Krakow Poland Inst Ferrous Met Ul Karola Miarki Gliwice Poland

Validation and further application of a coupled cellular automata - finite element model to investigate the influence of the degree of deformation on static recrystallization kinetics (SRX) during annealing of low carbon steels after cold rolling is presented within the work. Descriptions of major model components involving digital material representation finite element model as well as cellular automata approach for explicit static recrystallization simulations are presented. Obtained SRX results for various heating rates after 65% rolling reduction are validated with experimental data to assess the model's predictive capabilities. Finally, the validated model is used to investigate the influence of inhomogeneous energy distribution, obtained in the sample after rolling to 35, 50 and 65% reductions, on static recrystallization kinetics and grain size evolution. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Metals Annealing Recrystallization computer modelling and simulation

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Adsorption of hydrogen in Scandium/Titanium decorated nitrogen doped carbon nanotube

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MATERIALS CHEMISTRY AND PHYSICS 2016年 180卷 357-363页

作者： Mananghaya, Michael Belo, Lawrence Phoa Beltran, Arnel De La Salle Univ 2401 Taft Ave Manila 0922 Philippines DLSU STC Laguna Blvd Binan City Laguna Philippines PCIEERD DOST ASTHRDP Gen Santos Ave Taguig City 1631 Philippines

Nitrogen doped Carbon Nanotube with divacancy (4ND-CNxNT) that is decorated with Scandium and Titanium as potential hydrogen storage medium using the pseudo potential density functional method was investigated. Highly localized states near the Fermi level, which are derived from the nitrogen defects, contribute to strong Sc and Ti bindings, which prevent metal aggregation and improve the material stability. A detailed Comparison of the Hydrogen adsorption capability with promising system-weight efficiency of Sc over Ti was elucidated when functionalized with 4ND-CNxNT. Finally, the (Sc/4ND)(10)-CNxCNT composite material has a thermodynamically favorable adsorption and consecutive adsorption energy for ideal reversible adsorption and desorption of hydrogen at room temperature such that it can hold at least 5.8 wt% hydrogen molecules at the LDA and GGA level. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Adsorption computer modelling and simulation Desorption Nanostructures

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Nanotube diameter dependency of anisotropic pressure of an ionic liquid confined in a carbon nanotube: A molecular dynamics study for [emim][PF₆] case

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JOURNAL OF MOLECULAR LIQUIDS 2016年 220卷 370-374页

作者： Akbarzadeh, Hamed Abbaspour, Mohsen Khomarian, Elham Hakim Sabzevari Univ Fac Basic Sci Dept Chem Sabzevar *** Iran

We have presented molecular dynamics (MD) simulations of 1-ethyl-3-methylimidazolium hexafluorophosphate [emim][PF6] inside carbon nanotubes (CNTs) with different diameters. By considering the anisotropic pressure tensor for the ionic liquid inside the CNTs, the parameters of an equation of state (EoS) for the radial and axial directions have been derived. The nanotube diameter dependency of the EoS parameters has been also investigated. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Equations-of-state Molecular dynamics simulation Nanostructure computer modelling and simulation

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Magnetism and the low-energy electronic structure of Mott insulators K₂CoF₄ and SrMnO₃ perovskites

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MATERIALS CHEMISTRY AND PHYSICS 2016年 180卷 144-148页

作者： Nalecz, D. M. Radwanski, R. J. Ropka, Z. Pedag Univ Inst Phys PL-30084 Krakow Poland Ctr Solid State Phys Snt Filip 5 PL-31150 Krakow Poland

For Mott insulators, K2CoF4 and SrMnO3, we have calculated, in the purely ionic model, the low-energy electronic structure both in the paramagnetic and magnetic state as well as zero-temperature magnetic moment, its direction and its temperature dependence. We have calculated the octahedral crystal-field strength 10Dq to be 0.98 and 2.25 eV. We claim that for an adequate theoretical description of magnetic properties even small local distortions and the intra-atomic relativistic spin-orbit coupling have to be taken into account. Our studies have revealed a strong interplay of the magnetism, the orbital moment in particular, with the local crystallographic structure. The calculated orbital moment in K2CoF4 is very large, 1.06 mu(B), giving 30% contribution to the total moment - this result points the necessity to "unquench" the orbital magnetism in 3d compounds. We consistently described magnetic and some optical properties of these compounds, containing atoms with incomplete 3d shell, in agreement with their insulating ground state. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Magnetic materials computer modelling and simulation Crystal fields Magnetic properties

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Theoretical method for simulation of potential swing and double layer capacitance in electrolytes containing different cations

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MATERIALS CHEMISTRY AND PHYSICS 2016年第0期182卷 1-5页

作者： Chernyshev, Alfred P. Uvarov, Nikolai F. Russian Acad Sci Inst Solid State Chem & Mechanochem Siberian Branch Kutateladze St 18 Novosibirsk 630128 Russia Novosibirsk State Tech Univ Karl Marx Prospect 20 Novosibirsk 630073 Russia Novosibirsk State Univ Pirogova St 2 Novosibirsk 630090 Russia

This paper aims to describe potential swings on electrodes in different electrolytes by simple but accurate theoretical method. The electric double layer capacitance was considered for spherical nano electrodes operating in acetonitrile-based electrolytes. The model allows determining the potential swings via accounting for the finite ion size and the influence of the local electric field on the electrolyte dielectric permittivity. It is also possible to determine the thickness of Stern and diffuse layers. A series of acetonitrile solutions of the BE4- salts of Li, Na, K, Rb, Cs and [(CH3)(4)N]+BE4- were examined in a systematic study. In this study we investigate the potential swings dependence of the size of the solvation sphere around ions. It is shown that this solvation sphere significantly affects the total specific capacitance of the electrolytes under consideration. As simulating parameters of electric double layers under high concentrations we used the finite size of ions covered by solvation sphere, the chemical composition of electrolytes, and surface potential. Results of this study can be widely used to design electrochemical devices (e.g. electrodes and electrolytes for electrochemical sensors and electric energy storage devices) for novel technologies. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Interfaces computer modelling and simulation Molecular dynamics Electrochemical properties Surface properties Dielectric properties

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Encapsulation of lawrencium into C₆₀ fullerene: Lr@C₆₀ versus Li@C₆₀

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MATERIALS CHEMISTRY AND PHYSICS 2016年 177卷 437-441页

作者： Srivastava, Ambrish Kumar Pandey, Sarvesh Kumar Misra, Neeraj Univ Lucknow Dept Phys Lucknow 226007 Uttar Pradesh India Indian Inst Technol Dept Chem Kanpur 208016 Uttar Pradesh India

The position of Lawrencium (Lr) in the periodic table has been debated several times. It has been noticed that some fundamental properties of Lr differ from the other elements of the actinide series and closely resemble those of alkali metal. To be specific, the first ionization energy of Lr 4.96 eV [Nature 520 (2015) 209] lies within the range assigned to alkali metals. Motivated by this fact, we study Lr@C-60 for the first time and compared its electronic properties with those of Li@C-60. Using density functional theory and its time dependent version, we explore structures, vibrational infrared spectra, molecular orbital surfaces, density of states and electronic absorption spectra of Lr@C-60 and Li@C-60. We notice that although Lr resides very close to the centre of C-60 than Li does, the electronic properties of Lr@C-60 closely resemble those of Li@C-60. For instance, Lr@C-60 is as conducting and polarizable as Li@C-60 due to almost equal frontier orbital energy gap and mean polarizability. This study is expected to provide further evidence where Lr atom mimics the alkali metal. (C) 2016 Elsevier B.V. All rights reserved.

关键词： Fullerenes computer modelling and simulation ab initio calculations Electrical properties

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Human ventricular activation sequence and the simulation of the electrocardiographic QRS complex and its variability in healthy and intraventricular block conditions

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EUROPACE 2016年第SUPPL 4期18卷 4-15页

作者： Cardone-Noott, Louie Bueno-Orovio, Alfonso Minchole, Ana Zemzemi, Nejib Rodriguez, Blanca Univ Oxford Dept Comp Sci Oxford OX1 3QD England Univ Oxford British Heart Fdn Ctr Res Excellence Oxford OX1 3QD England INRIA Bordeaux Sud Ouest 200 Ave Vieille Tour F-33405 Talence France Fdn Bordeaux Univ IHU Liryc Electrophysiol & Heart Modeling Inst F-33600 Bordeaux France

Aims To investigate how variability in activation sequence and passive conduction properties translates into clinical variability in QRS biomarkers, and gain novel physiological knowledge on the information contained in the human QRS complex. Methods and results Multiscale bidomain simulations using a detailed heart-torso human anatomical model are performed to investigate the impact of activation sequence characteristics on clinical QRS biomarkers. Activation sequences are built and validated against experimentally-derived ex vivo and in vivo human activation data. R-peak amplitude exhibits the largest variability in terms of QRS morphology, due to its simultaneous modulation by activation sequence speed, myocardial intracellular and extracellular conductivities, and propagation through the human torso. QRS width, however, is regulated by endocardial activation speed and intracellular myocardial conductivities, whereas QR intervals are only affected by the endocardial activation profile. Variability in the apico-basal location of activation sites on the anterior and posterior left ventricular wall is associated with S-wave progression in limb and precordial leads, respectively, and occasional notched QRS complexes in precordial derivations. Variability in the number of early activation sites successfully reproduces pathological abnormalities of the human conduction system in the QRS complex. Conclusion Variability in activation sequence and passive conduction properties captures and explains a large part of the clinical variability observed in the human QRS complex. Our physiological insights allow for a deeper interpretation of human QRS biomarkers in terms of QRS morphology and location of early endocardial activation sites. This might be used to attain a better patient-specific knowledge of activation sequence from routine body-surface electrocardiograms.

关键词： Electrocardiogram QRS complex Activation sequence Variability computer modelling and simulation

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