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期刊介绍
  《npj 计算材料学》是在线出版、完全开放获取的国际学术期刊。发表结合计算模拟与设计的材料学一流的研究成果。本刊由中国科学院上海硅酸盐研究所与英国自然出版集团(Nature Publishing Group,NPG)以伙伴关系合作出版。
  主编为陈龙庆博士,美国宾州大学材料科学与工程系、工程科学与力学系、数学系的杰出教授。
  共同主编为陈立东研究员,中国科学院上海硅酸盐研究所研究员高性能陶瓷与超微结构国家重点实验室主任。
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Nanotwinned and hierarchical nanotwinned metals: a review of experimental, computational and theoretical efforts(金属纳米孪晶和多极纳米孪晶:实验、计算和理论进展) 
Ligang SunXiaoqiao He & Jian Lu
npj Computational Materials 4:6 (2018)
doi:10.1038/s41524-018-0062-2
Published online:05 February 2018
Abstract| Full Text | PDF OPEN

摘要:本综述介绍了金属纳米孪晶(NT)和多极纳米孪晶(HNT)面心立方(FCC)方面的最新研究进展。HNT结构是一种新颖的结构,与NT结构材料相比,具有更高的强度/延展性。本文主要关注金属材料中NT和HNT诸结构的实验、原子和理论方面的最新研究进展。介绍了用于制造NT和HNT结构的几种自下而上和自上而下的先进技术。采用塑性形变技术可成功诱导HNT结构的形成,而采用晶体生长的模式则几乎不能成功合成HNT结构。一些对NT和HNT FCC金属的分子动力学(MD)研究,揭示了诸如双晶间距、晶粒尺寸和塑性取向等纳米尺度效应能极大地改变NT和HNT金属的性能。与NT结构相比,HNT结构有可能开启材料学一些独特现象。此外,基于实验和MD模拟观测所揭示的现象和机制,人们现已提出了一系列理论模型。这些理论模型在其适用范围内,能有效描述NT和HNT两类金属的力学行为。到目前为止,HNT结构制造技术的发展,以及HNT结构对金属性能影响的研究,尚处于起步阶段。迫切需要进一步的探索来推动先进材料的设计   

Abstract:The recent studies on nanotwinned (NT) and hierarchical nanotwinned (HNT) face-centered cubic (FCC) metals are presented in this review. The HNT structures have been supposed as a kind of novel structure to bring about higher strength/ductility than NT counterparts in crystalline materials. We primarily focus on the recent developments of the experimental, atomistic and theoretical studies on the NT and HNT structures in the metallic materials. Some advanced bottom-up and top-down techniques for the fabrication of NT and HNT structures are introduced. The deformation induced HNT structures are available by virtue of severe plastic deformation (SPD) based techniques while the synthesis of growth HNT structures is so far almost unavailable. In addition, some representative molecular dynamics (MD) studies on the NT and HNT FCC metals unveil that the nanoscale effects such as twin spacing, grain size and plastic anisotropy greatly alter the performance of NT and HNT metals. The HNT structures may initiate unique phenomena in comparison with the NT ones. Furthermore, based on the phenomena and mechanisms revealed by experimental and MD simulation observations, a series of theoretical models have been proposed. They are effective to describe the mechanical behaviors of NT and HNT metals within the applicable scope. So far the development of manufacturing technologies of HNT structures, as well as the studies on the effects of HNT structures on the properties of metals are still in its infancy. Further exploration is required to promote the design of advanced materials. 

Design of high-strength refractory complex solid-solution alloys(高强度难熔复合固溶合金的设计) 
Prashant SinghAayush SharmaA. V. SmirnovMouhamad S. DialloPratik K. RayGanesh Balasubramanian & Duane D. Johnson
npj Computational Materials 4:16 (2018)
doi:10.1038/s41524-018-0072-0
Published online:28 March 2018
Abstract| Full Text | PDF OPEN

摘要:已知镍基高温合金和含钼近等原子高熵合金都具有较高的温度强度和耐腐蚀性。然而,复杂的固溶合金提供了巨大的设计空间,可在稍低熵的情况下调节最佳性能。对于难熔Mo-W-Ta-Ti-Zr合金来说,本研究通过相干势近似来展示KKR电子结构方法,以便在五维设计空间上鉴定合金,这种合金具有改进的力学性能和必要的全局(形成焓)和局部(短程有序)的稳定性。以经典分子动力学模拟为变形研究建模,以第一性原理数据作模拟结果的验证。我们预测稳定性得到改善的复合固溶合金,比近等原子情况下弹性模量大大提高(在300 K时提高3倍,与实验验证结果一致),温度在500 K以上时的合金弹性模量也比商业合金温度为2000 K时的模量高2.3倍。我们的研究还表明,鉴于关键的电子效应,最佳复合固溶体合金不能用经典势函数很好地加以描述   

Abstract:Nickel-based superalloys and near-equiatomic high-entropy alloys containing molybdenum are known for higher temperature strength and corrosion resistance. Yet, complex solid-solution alloys offer a huge design space to tune for optimal properties at slightly reduced entropy.For refractory Mo-W-Ta-Ti-Zr, we showcase KKR electronic structure methods via the coherent-potential approximation to identify alloys over five-dimensional design space with improved mechanical properties and necessary global (formation enthalpy) and local (short-range order) stability. Deformation is modeled with classical molecular dynamic simulations, validated from our first-principle data.We predict complex solid-solution alloys of improved stability with greatly enhanced modulus of elasticity (3× at 300 K) over near-equiatomic cases, as validated experimentally, and with higher moduli above 500 K over commercial alloys (2.3× at 2000 K).We also show that optimal complex solid-solution alloys are not described well by classical potentials due to critical electronic effects. 

Editorial Summary

Solid solutions: screening by electronic structure(固溶合金:通过电子结构筛选) 

本研究将第一性原理计算与电子合金设计标准相结合,来设计理想的复杂合金材料。美国爱荷华州立大学Duane Johnson教授等用密度泛函理论研究了由五种难熔元素(钼、钨、钽、钛和锆)构成的设计空间,并确定了用于冶炼高温强度和耐腐蚀性富钼合金的最佳组分。他们通过预测杨氏模量、短程原子有序等结构性质,以晶格常数确定每种组份的整体稳定性、快速筛选设计空间以选择出合金的最佳组分。分子动力学和实验测试结果均证实了预测的力学性能。这种电子结构方法可以帮助优化复杂溶固合金以提高其力学性能。

Combining first-principle calculations with electronic alloy design criteria lead to the identification of desirable complex alloys. A team led by Duane Johnson at Iowa State University, USA, applied density functional theory to explore the design space formed by five refractory elements (molybdenum, tungsten, tantalum, titanium, and zirconium) and identified optimal molybdenum-rich alloy compositions for high temperature strength and corrosion resistance.By predicting structural properties such as the Young’s modulus as well as the short-range atomic order, a lattice constant identified the global stability of each composition and allowed for the fast screening of the design space to select the best compositions.Both molecular dynamics and experimental testing confirmed the predicted mechanical properties. This electronic structure approach can help optimize complex solution alloys for enhanced mechanical properties.

 

Data analytics and parallel-coordinate materials property charts (数据分析与展示材料属性的可视化图表) 
Jeffrey M. Rickman
npj Computational Materials 4:5 (2018)
doi:10.1038/s41524-017-0061-8
Published online:29 January 2018
Abstract| Full Text | PDF OPEN

摘要:以图表形式展示材料性能关系的好处是突出重点,从而增强了我们对材料“结构-性能”关系的理解,也方便对材料的选择。然而,许多情况下,这些关系本质上是高度多维的,通常却使用属性空间的低维横截面来表达这些关系的某些方面。为了解决这个问题,本研究采用数据分析方法,结合可视化策略(即平行坐标)来更好地表示多维材料数据,找出性能之间的有用关系。本文通过对金属系和陶瓷系多维材料属性图表的构建和系统分析,阐明了这种方法的实用性。这些图表简化了高维几何图形的描述,实现了尺寸缩小以及重要属性关系的识别,强调了不同材料类别之间的区别   

Abstract:It is often advantageous to display material properties relationships in the form of charts that highlight important correlations and thereby enhance our understanding of materials behavior and facilitate materials selection. Unfortunately, in many cases, these correlations are highly multidimensional in nature, and one typically employs low-dimensional cross-sections of the property space to convey some aspects of these relationships. To overcome some of these difficulties, in this work we employ methods of data analytics in conjunction with a visualization strategy, known as parallel coordinates, to represent better multidimensional materials data and to extract useful relationships among properties. We illustrate the utility of this approach by the construction and systematic analysis of multidimensional materials properties charts for metallic and ceramic systems. These charts simplify the description of high-dimensional geometry, enable dimensional reduction and the identification of significant property correlations and underline distinctions among different materials classes. 

Editorial Summary

Materials analysis: visualizing and interpreting multidimensional materials data (材料分析:对多维材料数据的可视化展示及其解释) 

构建多维材料属性的图表可以更好地识别不同属性之间的关系。研究材料行为时,通常用二维图表分析来建立不同属性之间的关系。然而,材料属性之间的相关性通常非常复杂,要使材料的高维数据可视化、可作有意义的比较并不容易。来自美国Lehigh大学的Jeffrey Rickman,采用可视化策略(即平行坐标)的数据分析方法展示了能表现多维材料数据的一种新方法,以这样的方法可以提取出材料属性之间的有用关系。通过构建和分析金属系和陶瓷系的多维材料属性图,他们阐明了这一框架作用,为识别材料各属性之间的关系提供了强有力的工具。

Multidimensional materials property charts can be constructed to better identify the relationship among different properties. When investigating the behavior of materials, the relationship between different properties is usually established through analysis of two-dimensional charts. The correlation between properties is usually far more complex, but visualizing high-dimensional materials data in a way that enables meaningful comparisons is not easy. By employing methods of data analytics with a visualization strategy known as parallel coordinates, Jeffrey Rickman from Lehigh University demonstrates a new way to represent multidimensional materials data that allows useful relationships among properties to be extracted. The author demonstrates the power of this framework by constructing and analysing multidimensional materials properties charts for metallic and ceramic systems, showing that it provides a powerful tool for identifying property relationships.

 

Computational discovery of p-type transparent oxide semiconductors using hydrogen descriptor (采用氢描述子计算发现p型透明氧化物半导体) 
Kanghoon YimYong YounMiso LeeDongsun YooJoohee LeeSung Haeng Cho & Seungwu Han
npj Computational Materials 4:17 (2018)
doi:10.1038/s41524-018-0073-z
Published online:03 April 2018
Abstract| Full Text | PDF OPEN

摘要:终端透明电子器件需要互补且对称的n型和p型透明半导体对。虽然已经有几种n型透明氧化物半导体(如InGaZnO和ZnO)用于消费电子产品,但目前科学家们还未找到可与对应的n型半导体相媲美的p型氧化物。最近,利用密度泛函理论计算的高通量筛选法,研究者尝试着筛选出几种p型透明氧化物,但这些候选材料没有得到有效的实验验证,这意味着尚需更好的理论预测因子。本研究提出了一种高可靠性和高计算效率的p型掺杂因子——氢杂质能级。并验证了采用氢掺杂因子可以区分众所周知的p型和n型氧化物。使用氢掺杂因子,作者筛选了大多数二元氧化物和一系列三元化合物,它们涵盖了含Sn2+和含Cu1+的氧化物以及氧硫族元素化合物。依据筛选结果,本研究提出了两种富有前景的p型氧化物:La2O2Te和CuLiO   

Abstract:The ultimate transparent electronic devices require complementary and symmetrical pairs of n-type and p-type transparent semiconductors. While several n-type transparent oxide semiconductors like InGaZnO and ZnO are available and being used in consumer electronics, there are practically no p-type oxides that are comparable to the n-type counterpart in spite of tremendous efforts to discover them. Recently, high-throughput screening with the density functional theory calculations attempted to identify candidate p-type transparent oxides, but none of suggested materials was verified experimentally, implying need for a better theoretical predictor. Here, we propose a highly reliable and computationally efficient descriptor for p-type dopability—the hydrogen impurity energy.We show that the hydrogen descriptor can distinguish well-known p-type and n-type oxides.Using the hydrogen descriptor, we screen most binary oxides and a selected pool of ternary compounds that covers Sn2+-bearing and Cu1+-bearing oxides as well as oxychalcogenides.As a result, we suggest La2O2Te and CuLiO as promising p-type oxides. 

Editorial Summary

Transparent oxides: p-type hunting (透明氧化物:探寻p型半导体) 

该研究通过计算特定缺陷的形成能来筛选透明氧化物半导体,并揭示了一些很有前途的空穴掺杂候选对象。尽管p掺杂半导体可用于电子器件,但迄今为止它们的性能与其对应的n型半导体还相差甚远:大多数p型氧化物存在稳定性或透明度差的问题。现在,首尔大学和韩国大田电子与电信研究院的研究团队,通过计算来搜寻具有高导电性和良好透明度的p-掺杂氧化物。他们采用缺陷化学进行筛选,并用氢间隙缺陷的形成能和空穴质量进行估测,以此评定材料的掺杂能力。作者提出了一些有前途的p型二元氧化物和三元化合物,一旦它们的性能被实验所验证,将会在电子器件中发挥巨大的作用。

Computational studies screen transparent oxide semiconductors based on the formation energy of a particular defect, and reveal promising hole-doped candidates. Although p-doped semiconductors are useful for electronic devices, their performance so far is not comparable to their n-type counterparts: most p-type oxides have stability issues or suffer from poor transparency.Now a team from Seoul National University and the Electronics and Telecommunications Research Institute in Daejeon, South Korea, are computationally looking for p-doped oxides with high conductivity and good transparency, simultaneously. Their screening relies on defect chemistry and assesses the dopability of the materials by using the formation energy of hydrogen interstitial defect, as well as the evaluation of the hole mass.Authors put forth a few promising p-type binary oxides and ternary compounds, which can be very useful for implementing electronic devices, once their properties have been verified experimentally.

 

Review on modeling of the anode solid electrolyte interphase (SEI) for lithium-ion batteries(锂离子电池阳极固体电解质界面(SEI)模拟研究进展) 
Aiping WangSanket KadamHong LiSiqi Shi & Yue Qi
npj Computational Materials 4:15(2018)
doi:10.1038/s41524-018-0064-0
Published online:26 March 2018
Abstract| Full Text | PDF OPEN

摘要:固体电解质界面(SEI)是由电解质的分解产物在电极表面上形成的钝化层。SEI允许Li +传输但阻挡电子通过,以防止电解质进一步分解,并确保电化学反应能够持续进行。由于其复杂的结构,及缺乏可靠的原位实验技术,SEI纳米厚度膜的形成和生长机理尚未完全明了。计算方法方面的重大进展使得SEI形成机制的预测模拟成为可能。本文旨在从电子结构计算到介观尺度模拟,涵盖电解质还原反应的热力学和动力学、SEI形成、通过电解质设计改性、SEI性质与电池性能间的关联,以及人工SEI设计方面来概述阳极上SEI膜研究的最新模拟进展。本文还对多尺度模拟作了总结和比较,并与实验结果进行比较。本文还讨论了SEI基本性质的计算细节,如:电子隧道效应、锂离子传输、块体SEI和电极/(SEI/)电解质界面的化学/机械稳定性。该综述展示了计算方法在SEI特性解析和人工SEI设计中的应用潜力。我们相信,计算建模与实验相结合可以相互补充,从而更好地了解SEI的复杂性,以便将来开发高性能电池   

Abstract:A passivation layer called the solid electrolyte interphase (SEI) is formed on electrode surfaces from decomposition products of electrolytes. The SEI allows Li+ transport and blocks electrons in order to prevent further electrolyte decomposition and ensure continued electrochemical reactions.The formation and growth mechanism of the nanometer thick SEI films are yet to be completely understood owing to their complex structure and lack of reliable in situ experimental techniques.Significant advances in computational methods have made it possible to predictively model the fundamentals of SEI.This review aims to give an overview of state-of-the-art modeling progress in the investigation of SEI films on the anodes, ranging from electronic structure calculations to mesoscale modeling, covering the thermodynamics and kinetics of electrolyte reduction reactions, SEI formation, modification through electrolyte design, correlation of SEI properties with battery performance, and the artificial SEI design.Multi-scale simulations have been summarized and compared with each other as well as with experiments.Computational details of the fundamental properties of SEI, such as electron tunneling, Li-ion transport, chemical/mechanical stability of the bulk SEI and electrode/(SEI/) electrolyte interfaces have been discussed.This review shows the potential of computational approaches in the deconvolution of SEI properties and design of artificial SEI.We believe that computational modeling can be integrated with experiments to complement each other and lead to a better understanding of the complex SEI for the development of a highly efficient battery in the future. 

Temperature-dependent phonon spectra of magnetic random solid solutions (磁性随机固溶体的温度依赖性声子谱) 
Yuji IkedaFritz KörmannBiswanath DuttaAbel CarrerasAtsuto SekoJörg Neugebauer & Isao Tanaka
npj Computational Materials 4:7 (2018)
doi:10.1038/s41524-018-0063-1
Published online:28 February 2018
Abstract| Full Text | PDF OPEN

摘要:本研究基于第一原理开发了一种计算工具,用于热磁波动等方面的磁随机固溶体声子模拟。该方法考虑了由磁激发和由化学紊乱引起的力常数波动。这一方法可准确地预测Fe-Pd和Fe-Pt Invar两种合金中,能观察到的横向声学模式随温度升高而出现的异常声子硬化。这种在传统谐波图像中无法解释的奇特行为,竟然是热磁波动的结果。本方法有可能直接用来对多种材料的物理行为提出新的解释,也可用来计算设计目前尚没有的全新材料   

Abstract:A first-principles-based computational tool for simulating phonons of magnetic random solid solutions including thermal magnetic fluctuations is developed. The method takes fluctuations of force constants due to magnetic excitations as well as due to chemical disorder into account.The developed approach correctly predicts the experimentally observed unusual phonon hardening of a transverse acoustic mode in Fe–Pdan Fe–Pt Invar alloys with increasing temperature.This peculiar behavior, which cannot be explained within a conventional harmonic picture, turns out to be a consequence of thermal magnetic fluctuations. The proposed methodology can be straightforwardly applied to a wide range of materials to reveal new insights into physical behaviors and to design materials through computation, which were not accessible so far. 

Editorial Summary

Magnetic materials: Turning up the heat on disordered magnets (磁性材料:调节无序磁体的热量) 

该研究开发了一种数值方法,可用来预测零上温区的无序磁性固体的原子振动。有精确的计算方法方可计算材料在不同温度下的振动模式,才能基于第一原理确定材料的热力学性质。然而,原子不均匀分布和量子磁性行为二者对合金造成的影响,都需要用特殊方法处理才能计算。来自日本、德国和荷兰的Yuji Ikeda及其同事,将有序磁系统方法与已有无序材料近似方法结合起来,设计了一种新方法。该方法成功地捕捉了Invar合金的非凡热膨胀性能,原子和磁性波动相互作用对这种性能有强烈影响。他们的方法也可能为高熵合金等复杂材料的物理现象提供新的解释。

Researchers have developed a numerical method to predict the atomic vibrations of disordered magnetic solids above zero temperature. Accurate methods for computing the vibrational modes of materials at different temperatures are needed to determine thermodynamic properties from first principles.However, for magnetic alloys the effects of the non-uniform distribution of atoms and quantum magnetic behaviour each require special techniques for calculations to be tractable. Yuji Ikeda and colleagues from Japan, Germany and the Netherlands have designed a scheme that combines an approach for ordered magnetic systems with established approximations for disordered materials.Their method successfully captures the unusual thermal expansion properties of Invar alloys, which are strongly affected by the interplay of atomic and magnetic fluctuations, and should provide insights into the physics of other complex materials such as high entropy alloys.

 

Insight into point defects and impurities in titanium from first principles (基于第一原理深入探讨金属钛的点缺陷和杂质) 
Sanjeev K. NayakCain J. HungVinit SharmaS. Pamir AlpayAvinash M. DongareWilliam J. Brindley & Rainer J. Hebert
npj Computational Materials 4:11 (2018)
doi:10.1038/s41524-018-0068-9
Published online:16 March 2018
Abstract| Full Text | PDF OPEN

摘要:钛合金由于兼具强度、密度和耐腐蚀性等特性,被广泛用于航空和生物医用行业。近几十来的实验研究主要集中于理解其工艺-微结构-性能间的关系并极大的深化了相关的认识。点缺陷对于钛合金的力学性能影响显著,然而目前对于点缺陷的认识大都基于半经验的规则。本研究开展了自洽第一性原理的缺陷形成能计算,详细考察了本征缺陷,如空位和自间隙,及外来点缺陷,如间隙位和替代位杂质/掺杂元素等。我们发现大多数杂质元素,不论其原子半径大小,都倾向占据替代位,而强电负性元素,如C、N、O、F、S和Cl,其中部分元素为Ti中的常见杂质,则占据间隙位   

Abstract:Titanium alloys find extensive use in the aerospace and biomedical industries due to a unique combination of strength, density, and corrosion resistance. Decades of mostly experimental research has led to a large body of knowledge of the processing-microstructure-properties linkages. But much of the existing understanding of point defects that play a significant role in the mechanical properties of titanium is based on semi-empirical rules. In this work, we present the results of a detailed self-consistent first-principles study that was developed to determine formation energies of intrinsic point defects including vacancies, self-interstitials, and extrinsic point defects, such as, interstitial and substitutional impurities/dopants.We find that most elements, regardless of size, prefer substitutional positions, but highly electronegative elements, such as C, N, O, F, S, and Cl, some of which are common impurities in Ti, occupy interstitial positions. 

Editorial Summary

Defects: titanium impurities by first principles(缺陷:用第一原理考察钛杂质) 

相比半经验规则,第一性原理计算可以系统地预测金属钛中的杂质如何形成点缺陷。来自美国康涅狄格大学的Sanjeev Nayak和Rainer Herbert等采用密度泛函理论模拟了二十多种钛杂质的影响,包括前二十种化学元素,以及通常添加到钛中的过渡金属元素。研究表明,强电负性元素,如碳和氧等稳定占据钛晶格中的八面体间隙位,与钛的间隙缺陷类似。而金属杂质,如钒等,倾向占据替代位。晶格中的空位只有在远离钛间隙原子时才能稳定存在。针对点缺陷形成和稳定性的研究有助于更好地控制材料并将其用于各种先进制造工艺,诸如3D打印等。

First principles, not semi-empirical rules, can systematically predict how point defects form because of impurities in titanium. A team led by Sanjeev Nayak and Rainer Herbert at the University of Connecticut, USA, used density functional theory to model the effect of more than twenty impurities in titanium, including the first twenty chemical elements as well as transition metals commonly added to titanium. Electronegative elements such as carbon and oxygen were stable at octahedral interstitial positions in the titanium lattice, in an identical manner to interstitial titanium. In contrast, metallic impurities such as vanadium preferred substitutionalsites.Finally, vacancies in the lattice only persisted if they were far enough from their interstitial titanium atom. Research into point defect formation and stability may help us control materials for advanced manufacturing processes such as 3D printing.

 

Efficient first-principles prediction of solid stability: Towards chemical accuracy(第一原理有效预测固体稳定性:提高化学精度) 
Yubo ZhangDaniil A. KitchaevJulia YangTina ChenStephen T. DacekRafael A. Sarmiento-PérezMaguel A. L. MarquesHaowei PengGerbrand CederJohn P. Perdew & Jianwei Sun
npj Computational Materials 4:9 (2018)
doi:10.1038/s41524-018-0065-z
Published online:09 March 2018
Abstract| Full Text | PDF OPEN

摘要:材料稳定性问题对凝聚态物理和材料科学中任何系统性质的分析都具有根本上的重要意义。有关化学稳定性能力(即:在某些化学环境中化学计量组成是否能够保持)和结构选择(即:化学计量组成将采用何种晶体结构)的评价,对预测材料合成、反应性和性质至关重要。本研究证明密度泛函理论与最近开发的强约束-适当规范(strongly constrained and appropriately normed, SCAN)函数,在材料稳定问题的两个方面(化学稳定性能力&结构选择),对主要化合物群组能作可信的、有效的预测,而对过渡金属化合物的预测,虽然也有进展,但仍是一个挑战。因此,SCAN函数为元素周期表的一个重要部分提供了一个稳健的模型,为新材料的开发和精细相变研究提供了良机,即使在几乎没有实验数据的大量有待探测的系统中,SCAN函数也是个良好的模型   

Abstract:The question of material stability is of fundamental importance to any analysis of system properties in condensed matter physics and materials science. The ability to evaluate chemical stability, i.e., whether a stoichiometry will persist in some chemical environment, and structure selection, i.e. what crystal structure a stoichiometry will adopt, is critical to the prediction of materials synthesis, reactivity and properties.Here, we demonstrate that density functional theory, with the recently developed strongly constrained and appropriately normed (SCAN) functional, has advanced to a point where both facets of the stability problem can be reliably and efficiently predicted for main group compounds, while transition metal compounds are improved but remain a challenge. SCAN therefore offers a robust model for a significant portion of the periodic table, presenting an opportunity for the development of novel materials and the study of fine phase transformations even in largely unexplored systems with little to no experimental data. 

Displacement Current in Domain Walls of Bismuth Ferrite (铋铁氧体畴壁位错电流的研究) 
Sergey Prosandeev,Yurong Yang,Charles Paillard&L. Bellaiche
npj Computational Materials 4:8 (2018)
doi:10.1038/s41524-018-0066-y
Published online:8 March 2018
Abstract| Full Text | PDF OPEN

摘要:1861年,麦克斯韦构想了位移电流的概念,完善了电动力学定律,也使利用这种位移电流的器件得以实现。近来致力于畴的研究蓬勃兴起,畴在有畴铁系化合物中的相应电导率也有探讨,但有趣的是,目前尚不清楚这种位移电流是否在有畴铁系材料中引起大的内在交流电流。本研究报道了基于第一原理的原子模拟,用这些模拟对原型BiFeO3多铁材料作了预测:71°和109°畴的畴壁横向(极化相关)位移电流显著,频率达到GHz量级,实际上该电流与先前报道的直流电流(可能本质上是外部的、由电子引起的)至少处于同一数量级。人们发现,如此之大的局部内在交流电流源自于畴壁处的低频振动,可能为GHz或THz全新器件的设计打开了大门,而且这种情况下,电流还被限制在这个畴壁内   

Abstract:In 1861, Maxwell conceived the idea of the displacement current, which then made laws of electrodynamics more complete and also resulted in the realization of devices exploiting such displacement current. Interestingly, it is presently unknown if such displacement current can result in large intrinsic ac current in ferroic systems possessing domains, despite the flurry of recent activities that have been devoted to domains and their corresponding conductivity in these compounds. Here, we report first-principles-based atomistic simulations that predict that the transverse (polarization-related) displacement currents of 71° and 109° domains in the prototypical BiFeO3 multiferroic material are significant at the walls of such domains and in the GHz regime, and, in fact, result in currents that are at least of the same order of magnitude than previously reported dc currents (that are likely extrinsic in nature and due to electrons). Such large, localized and intrinsic ac currents are found to originate from low-frequency vibrations at the domain walls, and may open the door to the design of novel devices functioning in the GHz or THz range and in which currents would be confined within the domain wall. 

Editorial Summary

Domain wall electronics: More robust at high frequencies(畴壁电子学:高频率下更为活跃) 

本研究预测铋铁氧体的畴壁具有较高的交流电导率,可用于开发千兆和太赫兹设备。对绝缘功能材料导电畴壁的观察,提高了形成可重构电子电路的可能性。不幸的是,人们很难确定驱动直流畴壁导电的机制,虽然它似乎是由材料缺陷引起的,但没法据此制造精确控制的电子器件。来自美国阿肯色州立大学和俄罗斯南联邦大学的Sergey Prosandeev等使用数值模型表明,高频畴壁电导可能发生在多铁铋铁氧体中,由畴壁的固有物理性质决定。通过避免依赖外部因素,这样的畴壁导电机制可能为千兆赫电子系统的开发,提供更强大的平台。

Domain walls in bismuth ferrite are predicted to have high a.c. conductivity, which could be exploited to develop giga- and terahertz devices. The observation of conducting domain walls in otherwise insulating functional materials has raised the prospect of forming reconfigurable electronic circuits. Unfortunately, it has been difficult to definitively identify the mechanism driving d.c. domain wall conduction, although it appears to arise from material defects, making precisely controlled devices difficult to fabricate. Sergey Prosandeev and co-workers from the University of Arkansas, USA, and Southern Federal University, Russia, have used numerical modeling to show that high frequency domain wall conductivity can occur in multiferroic bismuth ferrite due to the intrinsic physics of the walls.By avoiding reliance on extrinsic factors this mechanism should provide a more robust platform for developing gigahertz regime electronics.

 

Bismuth and antimony-based oxyhalides and chalcohalides as potential optoelectronic materials(铋/锑基卤氧化物和硫卤化物作为潜在的光电材料) 
Zhao RanXinjiang WangYuwei LiDongwen YangXin-Gang ZhaoKoushik BiswasDavid J. SinghLijun Zhang
npj Computational Materials 4:14 (2018)
doi:10.1038/s41524-018-0071-1
Published online:22 March 2018
Abstract| Full Text | PDF OPEN

摘要:近十年来,ns2阳离子(如Pb2+和Sn2+)基卤化物(如混合钙钛矿太阳能吸收剂等)已成为最令人兴奋的新型光电材料之一。这些材料不仅在某些情况下表现出前所未有的性能,而且它们有可能以其出乎意料的性能(如对缺陷的极端耐受性)打开一片全新领域。然而,由于此类材料才刚出现不久,因此仍有很多化合物尚未得到充分探索。本研究采用连贯第一性原理法评价一系列铋/锑卤氧化物和硫卤化物,以确定其性质及其规律。基于这些计算,我们确定了一种由三种类型化合物组成的子集,有望用于太阳能吸收器、透明导体和辐射探测器。我们进一步探讨了它们的电子结构及其与晶体几何结构的关系,以及对带边扩散和载流子有效质量的影响   

Abstract:In the last decade the ns2 cations (e.g., Pb2+ and Sn2+)-based halides have emerged as one of the most exciting new classes of optoelectronic materials, as exemplified by for instance hybrid perovskite solar absorbers. These materials not only exhibit unprecedented performance in some cases, but they also appear to break new ground with their unexpected properties, such as extreme tolerance to defects. However, because of the relatively recent emergence of this class of materials, there remain many yet to be fully explored compounds. Here, we assess a series of bismuth/antimony oxyhalides and chalcohalides using consistent first principles methods to ascertain their properties and obtain trends.Based on these calculations, we identify a subset consisting of three types of compounds that may be promising as solar absorbers, transparent conductors, and radiation detectors.Their electronic structure, connection to the crystal geometry, and impact on band-edge dispersion and carrier effective mass are discussed. 

Editorial Summary

Optoelectronics: new kids in town (光电子学:城里新来的孩子) 

该研究以细致的第一性原理计算,揭示了铋基和锑基硫卤化物和卤氧化物在光电应用中的潜力。具有ns2的卤化物外层电子构型的离子,赋予卤化物光明的的应用前景(如太阳能电池)。该研究中,来自吉林大学、密苏里大学和阿肯色州立大学的科研人员,利用密度泛函理论研究了几种含铋或锑的ns2阳离子型硫卤化物和卤氧化物的性质。令人惊奇的是,某些铋基硫卤化物有望用于太阳能电池和室温辐射探测器,其带隙范围为1.5~2 eV。与此相对的是,一些带隙高于3eV卤氧化物是空穴导体,若可被掺杂,它们将可用作透明导电材料。该工作强调需要进一步的实验验证以充分评估该类材料在光电应用方面的潜力。

Detailed first-principles calculations reveal the potential of bismuth-based and antimony-based chalcohalides and oxyhalides for optoelectronics applications. The presence of ions with outer electron configuration of ns2in halides has rendered them very promising for applications, like solar cells.In this work, collaborators from Jilin University, University of Missouri, and Arkansas State University have used density functional theory to study the properties of several chalcohalides and oxyhalides containing bismuth or antimony ns2 cations.It turns out that certain bismuth-based chalcohalides are promising for solar cells applications and room-temperature radiation detectors, with bandgaps in the range 1.5–2 eV.Some oxyhalides, on the other hand, with bandgaps above 3 eV are hole-conducting, which makes them suitable for transparent conducting materials, if they can be doped. This work underlines that further experimental work is needed to fully assess the potential of this class of materials for optoelectronics applications.

 

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