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arXiv 2021年

作者： Wei, Haixin Zhao, Zekai Luo, Ray Departments of Materials Science and Engineering Molecular Biology and Biochemistry Chemical and Biomolecular Engineering and Biomedical Engineering Graduate Program in Chemical and Materials Physics University of California IrvineCA92697 United States

Implicit solvent models, such as Poisson-Boltzmann models, play important roles in computational studies of biomolecules. A vital step in almost all implicit solvent models is to determine the solvent-solute interface, and the solvent excluded surface (SES) is the most widely used interface definition in these models. However, classical algorithms used for computing SES are geometry-based, thus neither suitable for parallel implementations nor convenient for obtaining surface derivatives. To address the limitations, we explored a machine learning strategy to obtain a level-set formulation for the SES. The training process was conducted in three steps, eventually leading to a model with over 95% agreement with the classical SES. Visualization of tested molecular surfaces shows that the machine-learned SES overlaps with the classical SES on almost all situations. We also implemented the machine-learned SES into the Amber/PBSA program to study its performance on reaction field energy calculation. The analysis shows that the two sets of reaction field energies are highly consistent with 1% deviation on average. Given its level-set formulation, we expect the machine-learned SES to be applied in molecular simulations that require either surface derivatives or high efficiency on parallel computing platforms. © 2021, CC BY.

关键词： Solvents

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The failure of the Classical Nucleation Theory at low temperatures resolved

arXiv

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arXiv 2019年

作者： Cassar, Daniel R. Serra, André H. Peitl, Oscar Rodrigues, Alisson M. Zanotto, Edgar D. Vitreous Materials Laboratory Department of Materials Engineering Federal University of São Carlos São Carlos SP Brazil Federal University of Sao Carlos Graduate Program in Materials Science and Engineering

A relevant observation about crystal nucleation kinetics in glass-forming substances has been a matter of intense debate for several decades. The Classical Nucleation Theory (CNT) allegedly fails to describe the temperature dependence of the homogeneous crystal nucleation rates below the temperature of maximum nucleation rate. This failure was reported for several glass-forming substances and is known as nucleation "breakdown". Some reasonable explanations for this apparent break have been advanced in the literature, however, the simplest hypothesis has never been tested: that this break is a byproduct of nucleation datasets that have not reached the steady-state regime. In this work, we tested this hypothesis by thoroughly analyzing new and published nucleation data for supercooled Li2Si2O5, BaSi2O5, Na4CaSi3O9, and Na2Ca2Si3O9liquids, using only datasets for which steady-state conditions (likely) have been reached. For that purpose, we used three restraining conditions: i) Nucleation and diffusion data were measured in the same glass batch, and each batch was individually analyzed;ii) only nucleation rate data that passed a steady-state regime test were used in the analysis;iii) the uncertainty and regression confidence bands were computed and considered. With this strategy, we proved that the alleged nucleation break is indeed an experimental artifact! This result ends a four decade-old dilemma and corroborates the use of CNT for analyses of crystal nucleation rates. Copyright © 2019, The Authors. All rights reserved.

关键词： Silicates

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Elevated temperature-driven coordinative reconstruction of an unsaturated single-Ni-atom structure with low valency on a polymer-derived matrix for the electrolytic oxygen evolution reaction

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Nanoscale 2024年第15期16卷 7467-7479页

作者： Patil, Rahul Rajput, Anubha Matsagar, Babasaheb M. Chen, Norman C. R. Ujihara, Masaki Salunkhe, Rahul R. Yadav, Praveen Wu, Kevin C.-W. Chakraborty, Biswarup Dutta, Saikat Electrochemical Energy & Sensor Research Laboratory Amity Institute of Click Chemistry Research & Studies Amity University Noida India Department of Chemistry Indian Institute of Technology New Delhi India Department of Chemical Engineering National Taiwan University Taipei10617 Taiwan Molecular Science and Technology Program Taiwan International Graduate Program Academia Sinica Taiwan National Taiwan University Taiwan Graduate Institute of Applied Science and Technology National Taiwan University of Science and Technology Taipei Taiwan Materials Research Laboratory Department of Physics Indian Institute of Technology Jammu India Synchrotron X-ray Facility Raja Ramanna Centre for Advanced Technology Rajendra Nagar Madhya Pradesh 452013 Indore India

A high-temperature pyrolysis-controlled coordination reconstruction resulted in a single-Ni-atom structure with a Ni-Nx-C structural unit (x = N atom coordinated to Ni). Pyrolysis of Ni-phen@ZIF-8-RF at 700 °C resulted in NiNP-NC-700 with predominantly Ni nanoparticles. Upon elevating the pyrolysis temperature from 700 to 900 °C, a coordination reconstruction offers Ni-Nx atomic sites in NiSA-NC-900. A combined investigation with X-ray absorption spectroscopy, X-ray photoelectron spectroscopy, and soft X-ray L3-edge spectroscopy suggests the stabilization of low-valent Niδ+ (0 −2 was achieved. The cell potential recorded with Pt(−)/(+)NiSA-NC-900/NF was much lower than that obtained for other cells, i.e., Pt(−)/NF and NF(−)/(+)NF, which enhances the potentials of low-valent NiSAs for insightful understanding of the OER. At a constant applied potential of 1.61 V (vs. RHE) for 12 h, an small increase in current for initial 0.6 h followed by a constant current depicts the fair stability of catalyst for 12 h. Our results offer an insightful angle into the OER with a coordinatively reconstructed single-Ni-atom structure at lower valency ( © 2024 The Royal Society of Chemistry.

关键词： Reaction kinetics

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Development of Avrami's kinetics to describe growth of Bi-2223 crystals

Development of Avrami's kinetics to describe growth of Bi-22...

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2011 International Conference on Applied Superconductivity and Electromagnetic Devices, ASEMD 2011

作者： Chen, Wu Ming Jiang, Xu Chuan Yavuz, Mustafa Kambe, Shiro School of Materials Science and Engineering University of New South Wales Sydney NSW 2052 Australia Waterloo Institute for Nanotechnology University of Waterloo Waterloo ON N2L 3G1 Canada Human Sensing Program Graduate School of Science and Engineering Yamagata University 4-3-16 Johnan Yonezawa 992-8510 Japan

ISBN: (纸本)9781424478521

The Avrami's kinetics was known to be the best theory to describe Bi-2223 crystals growth. Whereas, it cannot explain the fact that maximum product volume appearing at optimum sintering time during synthesis Bi-2223 crystal. Meanwhile, the Avrami's equation can also be used to determine the activation energy of Bi-2223 crystal growth;unfortunately, the determined activation energy, E, had dispersion as much as hard to be accepted by researchers themselves. To solve those problems, we studied and developed Avrami's kinetics and obtained a developed Avrami's kinetics equation in this research. With the developed Avrami equation, the index of growth, n, and E of Bi-2223 crystals were determined, including the periods of Bi-2223 crystals growing and decomposing. The n and E for Bi-2223 crystals were changing during synthesis period, values of which can be positive, zero or negative for different reaction periods. And the negative E and n were no reports to be found before, which caused by the decomposition of the product. The developed kinetics can describe a phase transformation system that with metastable or stable product. The developed kinetics theory, as a universal theoretical tool, is expected to be widely applied in the science and engineering multidisciplines and their related interdisciplines. © 2011 IEEE.

关键词： Activation energy

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Terahertz Magnetospectroscopy of Gadolinium Gallium Garnet in Fields up to 25 T

Terahertz Magnetospectroscopy of Gadolinium Gallium Garnet i...

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JSAP-OSA Joint Symposia, JSAP 2021

作者： Bao, J. Peraca, N. Marquez Tay, F. Kritzell, T.E. Li, X. Noe, G.T. Katayama, I. Takeda, J. Nojiri, H. Yamahara, H. Tabata, H. Baydin, A. Kono, J. Department of Physics and Astronomy Rice University HoustonTX United States Department of Electrical and Computer Engineering Rice University HoustonTX United States Applied Physics Graduate Program Smalley-Curl Institute Rice University HoustonTX United States Department of Physics Graduate School of Engineering Science Yokohama National University Yokohama Japan Institute for Materials Research Tohoku University Sendai Japan Department of Electrical Engineering and Information Systems Graduate School of Engineering University of Tokyo Japan Smalley-Curl Institute Rice University HoustonTX United States Department of Materials Science and NanoEngineering Rice University HoustonTX United States

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Phosphors as Sensors for Radiation-Induced Displacement Damage

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MRS Online Proceedings Library 2012年第1期1471卷 68-74页

作者： Gollub, S. L. Harl, R. R. Weeden-Wright, S. L. Rogers, B. R. Walker, D. G. Interdisciplinary Graduate Program in Materials Science Vanderbilt University USA Department of Chemical and Biomolecular Engineering Vanderbilt University USA Department of Electrical Engineering Vanderbilt University USA Department of Mechanical Engineering Vanderbilt University USA

The radiation-induced displacement damage in yttrium borate (YBO3) is studied under X-ray, proton, and alpha irradiation. The photoluminescence (PL) was tested before and after irradiation to determine whether damage occurred and whether it could be queried by examining the PL spectrum. Two different dopants (cerium and europium) were used to activate the phosphor because each provides not only a different spectral signature but also a different mechanism for altering the spectrum between the pre- and post-PL measurements. X-rays, being primarily ionizing radiation, did not show any significant change between the pre and post measurements. We expected protons and alphas to damage the crystal structure, evidence of which could be seen in the change in the spectra before and after irradiation. However, we found no change under alpha exposure (3.6 × 1010 particles/cm2) and a significant change after proton exposure (5 × 1015 particles/cm2). While the material appears to be sensitive to protons, we cannot rule out its sensitivity to alphas because the alpha fluence may be too low to show an effect. This result provides strong indication that our materials are being damaged by particle radiation and that the radiation effects can be quantified.

关键词： luminescence radiation effects optical properties

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Enhancement of Interface Properties between Passivation Layers and InSb by Using Remote PECVD

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AIP Conference Proceedings 2011年第1期1399卷 105-106页

作者： Jaeyel Lee Jong‐Seok Woo Sehun Park Jungsub Kim Changjae Yang Sujin Kim Chulkyun Seok Kang Il Lee Jinsub Park Min‐Koo Han Kwang‐Seok Seo Euijoon Yoon aDepartment of Materials Science and Engineering Seoul National University Seoul Korea dDepartment of Electrical Engineering Seoul National University Seoul Korea bHybrid Materials Program (WCU) Department of Materials Science and Engineering Seoul National University Seoul Korea cDepartment of Nano Science and Technology Graduate School of Convergence Science and Technology Seoul National University Suwon Korea

We report the enhanced interface properties between passivation layers and InSb by using remote PECVD system. SiO2 and Si3N4 layers deposited by remote PECVD showed lower interface trap densities than layers deposited by normal PECVD. SiO2 layers deposited by remote PECVD showed 7.1×1011 cm−2 eV−1 of interface trap density at midgap which is slightly lower than SiO2 layers deposited by PECVD. Si3N4 layers deposited by remote PECVD showed 1.6∼1.7×1012 cm−2 eV−1 at midgap which is 3 times lower than Si3N4 layers deposited by PECVD. Interface properties of SiO2 are superior to that of Si3N4 in both case of PECVD and remote PECVD. To investigate the interface properties between SiO2 and InSb, X‐ray photoelectron spectroscopy was conducted. Indium and antimony oxide phases were found at the interface and these oxide phases could act as the origin of interface traps.

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ZnO AS AN INDUCER OF SPINEL-LIKE PHASE FORMATION ON ALUMINA-BASED CASTABLES 17

ZnO AS AN INDUCER OF SPINEL-LIKE PHASE FORMATION ON ALUMINA-...

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17th Unified International Technical Conference on Refractories, UNITECR 2022

作者： Borges, O.H. Sardelli, J.A.P. Rocha, R.M. Neto, C. Pagliosa Pandolfelli, V.C. Federal University of Sao Carlos Graduate Program in Materials Science and Engineering SP Sao Carlos Brazil FIRE Associate Laboratory SP Sao Carlos Brazil RHI Magnesita Research and Development Center Praça Louis Ensch 240 MG Contagem32210-902 Brazil

Environmental and occupational issues regarding Cr6+ formation urge the replacement of chrome-containing refractories by greener alternatives. For the latest decades, magnesium-containing refractories have been investigated for this purpose, however, few studies evaluated the likelihood of using other chemical elements as inducers of spinel-like phase formation in refractory castables. In this work, the addition of zincite (ZnO) in alumina-based vibrated castables bonded with calcium aluminate cement (CAC) or hydratable alumina (HA) was evaluated and compared with its MgO counterpart. The formation of the Zn-based spinel (ZnAl2O4, gahnite) took place at a lower temperature (1100 ºC) than MgAl2O4 (1300 ºC), resulting in the anticipated strengthening of these compositions. Despite the challenges regarding using ZnO - as its volatilization under reduced atmosphere and fast reaction kinetics -, lower linear dimensional changes, comparable cold modulus of rupture and enhanced thermal shock damage resistance was detected. © 2022 Unified International Technical Conference on Refractories, UNITECR 2022 - Proceedings. All rights reserved.

关键词： Zinc oxide

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Vibrational entropies of oxygen vacancy formation in metal oxides

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Physical Review materials 2024年第5期8卷 055407-055407页

作者： Bianca Baldassarri Jiangang He Christopher Wolverton Graduate Program in Applied Physics Northwestern University Evanston Illinois 60208 USA Department of Materials Science and Engineering Northwestern University Evanston Illinois 60208 USA

Oxygen vacancies play a key role in many energy-related applications, and the investigation of the thermodynamic forces driving their formation across different materials can be tackled through the use of ab initio methods. In this context, however, computational studies targeting finite-temperature properties such as entropy remain scarce. Wider-ranging studies are of interest to deepen the understanding of the role of the entropy of oxygen vacancy formation and its different components in processes like the ones involved in solar thermochemical hydrogen (STCH) production, and to investigate the existence of common trends and differences between materials. In this work, we use density functional theory and harmonic phonon calculations to compute the vibrational entropy of oxygen vacancy formation (ΔSvib) for 10 different metal oxide compounds. The computation is carried out by taking the difference between the vibrational entropy of a vacancy-containing and a pristine structure, while the entropic contribution from the final gaseous state of the oxygen lost from the material is accounted for separately with a gas entropy term. We first examine the temperature dependence of ΔSvib and highlight the presence of an initial peak around room temperature, followed by a steady decrease resulting from the presence of an additional O atom (the one becoming vacant) in the defect-free structure. We then inspect the atomic contributions to ΔSvib, and highlight similarities and differences between compounds. Finally, we consider other significant sources of entropy, and find ΔSvib to provide a smaller, yet non-negligible, contribution to the total entropy of vacancy formation. We also compare the temperature dependence of ΔSvib to that of the gas entropy, and show that the two largely counterbalance each other at high temperatures.

关键词： Entropy Hydrogen production Density functional theory

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Intrinsic Raman signatures of pristine hybrid perovskite CH3NH3PbI3 and its multiple stages of structure transformation 44

Intrinsic Raman signatures of pristine hybrid perovskite CH3...

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44th IEEE Photovoltaic Specialist Conference, PVSC 2017

作者： Chen, Qiong Liu, Henan Kim, Hui-Seon Liu, Yucheng Yang, Mengjin Yue, Naili Ren, Gang Zhu, Kai Liu, Shengzhong Frank Park, Nam-Gyu Zhang, Yong Department of Electrical and Computer Engineering Korea Republic of Optical Science and Engineering Graduate Program University of North Carolina at Charlotte CharlotteNC28223 United States School of Chemical Engineering and Department of Energy Science Sungkyunkwan University Suwon440-746 Korea Republic of Key Laboratory of Applied Surface and Colloid Chemistry National Ministry of EducationInstitute for Advanced Energy Materials School of Materials Science and Engineering Shaanxi Normal University Xi'an710062 China Chemical and Materials Science Center National Renewable Energy Laboratory GoldenCO80401 United States Molecular Foundry Lawrence Berkeley National Laboratory BerkeleyCA94720 United States

ISBN: (纸本)9781509056057

By performing spatially resolved Raman and photoluminescence spectroscopy with different illumination conditions, we have achieved a unified understanding towards the spectroscopy signatures of the organic-inorganic hybrid perovskite, transforming from the pristine state (CH3NH3PbI3 or MAPbI3) to fully degraded state (i.e., PbI2), for samples with varying crystalline domain size from mesoscopic scale to macroscopic size, synthesized by three different techniques. © 2017 IEEE.

关键词： Perovskite

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