Room temperature quantum anomalous Hall insulator in honeycomb lattice, RuCS_(3), with large magnetic anisotropy energy

The quantum anomalous Hall(QAH) effect has attracted enormous attention since it can induce topologically protected conducting edge states in an intrinsic insulating material. For practical quantum applications, the main obstacle is the non-existent room temperature QAH systems, especially with both large topological band gap and robust ferromagnetic order. Here, according to first-principles calculations, we predict the realization of the room temperature QAH effect in a two-dimensional(2D) honeycomb lattice, RuCS_(3) with a non-zero Chern number of C = 1. Especially, the nontrivial topology band gap reaches up to 336 me V for RuCS_(3). Moreover, we find that RuCS_(3) has a large magnetic anisotropy energy(2.065 me V) and high Curie temperature(696 K). We further find that the non-trivial topological properties are robust against the biaxial strain. The robust topological and magnetic properties make RuCS_(3) have great applications in room temperature spintronics and nanoelectronics.

Effect of grain boundary energy anisotropy on grain growth in ZK60 alloy using a 3D phase-field modeling

A three-dimensional(3D)multiple phase field model,which takes into account the grain boundary(GB)energy anisotropy caused by texture,is established based on real grain orientations and Read-Shockley model.The model is applied to the grain growth process of polycrystalline Mg(ZK60)alloy to investigate the evolution characteristics in different systems with varying proportions of low-angle grain boundary(LAGB)caused by different texture levels.It is found that the GB energy anisotropy can cause the grain growth kinetics to change,namely,higher texture levels(also means higher LAGB proportion)result in lower kinetics,and vice versa.The simulation results also show that the topological characteristics,such as LAGB proportion and distribution of grain size,undergo different evolution characteristics in different systems,and a more serious grain size fluctuation can be caused by a higher texture level.The mechanism is mainly the slower evolution of textured grains in their accumulation area and the faster coarsening rate of non-textured grains.Therefore,weakening the texture level is an effective way for implementing a desired homogenized microstructure in ZK60 Mg alloy.The rules revealed by the simulation results should be of great significance for revealing how the GB anisotropy affects the evolution of polycrystalline during the grain growth after recrystallization and offer the ideas for processing the alloy and optimizing the microstructure.

Simulation of facet dendrite growth with strong interfacial energy anisotropy by phase field method

Numerical simulations based on a new regularized phase-field model were presented, to simulate the solidification of hexagonal close-packed materials with strong interfacial energy anisotropies. Results show that the crystal grows into facet dendrites,displaying six-fold symmetry. The size of initial crystals has an effect on the branching-off of the principal branch tip along the<100> direction, which is eliminated by setting the b/a(a and b are the semi-major and semi-minor sizes in the initial elliptical crystals, respectively) value to be less than or equal to 1. With an increase in the undercooling value, the equilibrium morphology of the crystal changes from a star-like shape to facet dendrites without side branches. The steady-state tip velocity increases exponentially when the dimensionless undercooling is below the critical value. With a further increase in the undercooling value, the equilibrium morphology of the crystal grows into a developed side-branch structure, and the steady-state tip velocity of the facet dendrites increases linearly. The facet dendrite growth has controlled diffusion and kinetics.

Size effect of fracture characteristics for anisotropic quasi-brittle geomaterials

Understanding the size effect exhibited by the fracture mechanism of anisotropic geomaterials is important for engineering practice. In this study, the anisotropic features of the nominal strength, apparent fracture toughness, effective fracture energy and fracture process zone(FPZ) size of geomaterials were first analyzed by systematic size effect fracture experiments. The results showed that the nominal strength and the apparent fracture toughness decreased with increasing bedding plane inclination angle.The larger the specimen size was, the smaller the nominal strength and the larger the apparent fracture toughness was. When the bedding inclination angle increased from 0° to 90°, the effective fracture energy and the effective FPZ size both first decreased and then increased within two complex variation stages that were bounded by the 45° bedding angle. Regardless of the inherent anisotropy of geomaterials,the nominal strength and apparent fracture toughness can be predicted by the energy-based size effect law, which demonstrates that geomaterials have obvious quasi-brittle characteristics. Theoretical analysis indicated that the true fracture toughness and energy dissipation can be calculated by linear elastic fracture mechanics only when the brittleness number is higher than 10;otherwise, size effect tests should be adopted to determine the fracture parameters.

The effect of interfacial energy anisotropy on planar interface instability in a succinonitrile alloy under a small temperature gradient

The morphological stability of a planar interface with different crystallographic orientations is studied under a small positive temperature gradient using a transparent model alloy of succinonitrile. Novel experimental apparatus is constructed to provide a temperature gradient of about 0.37 K/mm. Under this small temperature gradient, the planar interface instability depends largely on the crystallographic orientation. It is shown experimentally that the effect of interfacial energy anisotropy on planar interface stability cannot be neglected even in a small temperature gradient system. Higher interfacial energy anisotropy leads the planar interface to become more unstable, which is different from the stabilizing effect of the interfacial energy on the planar interface. The experimental results are in agreement with previous theoretical calculations and phase field simulations.

Negative dependence of surface magnetocrystalline anisotropy energy on film thickness in Co_(33)Fe_(67) alloy

In this work, the magnetocrystalline anisotropy energy(MAE) on the surface of FeCoalloy film is extracted from x-ray magnetic linear dichroism(XMLD) experiments. The result indicates that the surface MAE value is negatively correlated with thickness. Through spectrum calculations and analysis, we find that besides the thickness effect, another principal possible cause may be the shape anisotropy resulting from the presence of interface roughness. These two factors lead to different electron structures on the fermi surface with different exchange fields, which produces different spin–orbit interaction anisotropies.

Electric Anisotropy and Two－dimensional Energy Band of Undoped and Heavily Doped Polyacetylene

ased on the known crystal data , we used the EHMACC(EHMO/CO) methodto calculate the twotlimensional energy band of both undoped and heavily iodine-doped polyacetylene (PA). The results show that (1 ) I-doping obviously reducesthe niagnitudes of Eg , Egi; (2) in the conducting process along the direction per-pendicular to PA chain , the P-type AO of iodine plays a very important role, i- e. ,the conducting bridge to transport the charge between the two neighbor PA chains.I-doping reniarkably increases σ_T value while the conducting process will reduce theratio magnitude of σ/σ. Therefore, heavily I-doping makes PA change fromsimeconductor to conductor which obviously has 2-D conductive ability.

Earth’s Serious Anisotropy, Non-Inertiality, Ether, Gain of Free Energy, Revealed, Part 2

The present paper is of historic importance as well as the second part of [1]. In this second part, we detect important details about the orbit of the Earth and about the velocity (of magnitude 217 km/s) of the solar system around the center of the Milky Way galaxy. Some of these details concern the perihelion and aphelion of the orbit of the Earth. For several years we have observed that the return pulses, on the oscilloscope screen, appear to be more energetic than the initial pulses (See Part 1, Figure 2, for which the blue return pulse crests are much higher than the yellow initial crests). The used oscilloscope is and only must be, a storage oscilloscope, in other words, a computerized oscilloscope with a digital memory. The first oscilloscopes like this, came out, only after 1995, a relatively recent time that all wire velocity experiments and measurements were already completely investigated by science. We do astronomy, without receiving images by an astronomical telescope, but instead by sending signals around a loop and making an analysis using the same oscilloscope as in Part 1. We recommend to the reader to study Part 1 as a prerequisite. The Earth surface is accelerating with a centripetal acceleration, due to its rotation, thus it is not an inertial frame. Also, the Earth is evidently anisotropic, due to the same rotation, a second reason for it being a non-inertial rotating frame.

Effect of seed layers on the static and dynamic magnetic properties of CoIr films with negative effective magnetocrystalline anisotropy

The c-axis oriented hcp-Co_(81)Ir_(19)magnetic films were prepared on different seed layers(Ni,Cu,Ir,Pt,Au,and No seed).We systematically investigated the impact that surface-free energy and strain energy have on the orientation and defects and/or internal stress of the grains by increasing the lattice mismatch ratio.Moreover,the initial permeability and the natural resonance frequency were discussed in great detail using a comparison between calculated values and experimental values.We found that the almost unchanged 4πM_(s) andμ_(i) are not affected,while the changed H_(c),intrinsic K_(grain),and f_(r) are strongly dependent on the seed layer and seed layer material.Moreover,the extracted damping constant is sensitive to the defects and/or internal stress and orientation of the grains.Therefore,the soft magnetic properties and microwave properties are adjusted and optimized by seed layers with different materials.

基于磁各向异性的管壁应力集中区域检测方法

针对应力集中导致管壁发生屈服失效的问题,提出了利用磁各向异性检测管壁应力集中区域的方法。从能量角度出发,研究了应力导致管壁产生磁各向异性的机理,建立了管壁当量应力与磁各向异性探头输出电压信号的数学模型,通过计算管壁的当量应力判断其是否发生屈服失效,搭建了应力检测实验平台。实验结果表明,应力会导致管壁产生磁各向异性,磁各向异性检测方法能够检测出管壁当量应力的变化趋势和主应力方向所在延长线的角度,进而判断管壁是否产生应力集中区域。

黄铁矿晶体断裂机制与表面反应性研究

通过密度泛函理论、断裂键参数和晶体结构分析,本文研究了黄铁矿晶体各向异性、晶体断裂规律及表面反应性。研究结果表明,黄铁矿晶体中存在Fe—S和S—S两种化学键,且Fe—S键的键能高于S—S键。Fe—S键与S—S键强度不等导致晶面断裂键密度与表面能关系不显著。通过引入化学键能量参数,本文得出晶面断裂能密度更适合分析黄铁矿晶体断裂机制和预测表面能,进而从晶体化学的角度解释了黄铁矿(100)、(111)、(210)、(110)面的表面能及其在晶体断裂时出现的困难程度依次增加的趋势,同时明确了黄铁矿常见暴露面的位点配位性质。基于此,研究得出黄铁矿表面低配位数的位点活性相对较强,从晶体化学的角度阐述了含金黄铁矿具有良好可浮性以及黄铁矿不同晶面氧化性差异的机理。

循环加卸载下黑云母石英片岩的弹性模量与能量演化特征研究

黑云母石英片岩是一种典型的各向异性岩石,为研究其损伤演化规律及各向异性表现特征,针对含0°,45°,90°3种片理角度的试样,开展了等塑性应变循环加卸载试验。结果表明:不同片理面角度试样的破坏模式有所不同,0°片理面试样中的张拉破裂现象与45°片理面中的剪切破坏现象尤为明显。随着塑性应变增加,黑云母石英片岩的弹性模量表现出先强化、后弱化的现象,这一现象在高围压下更为明显。在弱化阶段中,弹性模量演化的转折点与裂纹起裂强度σci稳定时对应塑性应变一致。弹性模量作为岩石损伤劣化过程的评价指标较完整性系数受片理面角度的影响更小。在岩石内部能量演化过程中,耗散能大小与片理面角度的关系为0°>90°>45°,耗散能、弹性能下降的速率大小关系为45°>90°>0°,其降至稳定时与岩石损伤强度σcd稳定时对应塑性应变一致。该研究借助弹性模量和能量演化规律分析,探究了黑云母石英片岩的损伤演化力学行为。

考虑磁畴偏转的无取向硅钢应力各向异性磁致伸缩特性模拟

无取向硅钢铁心的电磁振动是电机噪声的根本来源,采用夹件固定铁心可有效抑制其振动,但夹紧力施加不当会加剧铁心振动,原因为应力使无取向硅钢的磁畴取向发生偏转而引起磁致伸缩形变增大,形成应力各向异性。因此,为了获得准确的应力加载方法,需建立考虑磁畴偏转的无取向硅钢应力各向异性磁致伸缩模型。首先,求解自由能模型并计算能量极值点的分布,模拟无取向硅钢在磁场和应力作用下的磁畴偏转路径;其次,用磁晶各向异性能、应力各向异性能以及磁场能贡献的总和表示无磁滞磁化强度,将自由能模型与考虑磁滞的磁致伸缩模型相结合,通过无取向硅钢磁致伸缩特性测试获取模型参数并进行参数依赖性分析;最后,模拟应力与磁场作用下不同磁化方向的无取向硅钢的磁滞特性和磁致伸缩特性,通过仿真结果与实验结果的对比验证了该模型的准确性。结果表明,应力的增大会使无取向硅钢磁致伸缩应变值减小,同一应力下,磁致伸缩应变的大小会随磁化角度的增大而增大,该文所提出的应力各向异性磁致伸缩模型可以有效模拟此种变化规律。

渗透率各向异性对地热电池高效储能发电系统的影响

在当前能源转型的大背景下,清洁能源利用的创新技术市场日益扩大。地热电池储能发电技术有望解决太阳能、风能等可再生能源间歇性问题,受到清洁能源领域的关注。地热电池储能系统利用沉积地层中形成的低渗透率、低孔隙度的盖层和基层以及高渗透率、高孔隙度的中间储层实现热水的储存。这些热水创造了一个高温地热储层,已有研究表明这些储热可以高效回收,甚至可能实现长期甚至季节性的存储。在沉积结构中,其物理特征等方面存在十分明显各向异性,其中渗透率各向异性在流体的流动过程中发挥着重要作用。因此,研究渗透率各向异性对储能产能的影响至关重要。本研究利用TOUGHREACT-FLAC3D耦合软件建立了地热储能温度场—渗流场—应力场(THM)多场耦合模型,模拟了4种渗透率各向异性的情况,并分析了4种条件下热水注入和生产中热水流动路径、温度和压力的分布以及发电效率。结果表明:(1)渗透率各向异性对注采过程中压力的演变有强烈的影响,压力锋面在渗透率大的方向快速移动,而且各向异性越小,储层等效渗透率越大,注入热水需要的压力越小。(2)热水流动优先在渗透率大的方向流动,温度和压力的传播与热水流动方向一致,但是温度分布主要由流体流动的方向决定,在流动过程中热水用于加热初始环境中较冷的岩石和水造成热量损失,所以渗透率各向异性对储层温度的分布情况影响较小。(3)储层的岩石在高温热水的作用下发生膨胀,其孔隙压力恢复值随温度的升高逐渐高于储层初始的孔隙压力(12 MPa)。(4)在进行的30个注采循环结束后渗透率各向异性为1000时产生的电量最高可以达到5.2 MW。因此,在地热电池储能系统进行选取时,选择水平方向与垂直方向渗透率各向异性大的储层产能效率更高。

渗透率各向异性对CAESA系统季节性运行性能的影响

【目的】储层岩石渗透率通常呈各向异性分布,探究储层岩石渗透率各向异性对含水层压缩空气储能(compressed air energy storage in aquifers,CAESA)系统季节性运行性能的影响。【方法】建立CAESA系统概念模型和三维井群-储库数值模型,拟定3种储层渗透率各向异性分布方案,运用T2WELL/EOS3数值模拟软件,研究CAESA系统在季节性运行模式和渗透率各向异性条件下的流体传质和传热过程。【结果】储层渗透率各向异性会影响井筒-储层中的气相运移、流体交互和温压传递过程,进而影响系统的储能效率;当渗透率横纵比从2.0升高至10.0时,井筒的最大压力降低2.79 MPa,抽采阶段井口的最高温度升高2.06℃,井口两相流现象出现的时间从系统运行第435 d提前至第410 d,系统储能效率从89.8%降低至60.1%。【结论】对于渗透率各向异性程度较高的储层,可以通过增加初始气囊注入量或在后期进行补气来增加系统支撑压力,还可以采用注浆等工程手段,建立人造低渗边界以优化储层条件,提升系统储能效率。

各向异性对地震波勘探信号时-深转换的影响

基于Thomsen岩石各向异性参数,计算了各向异性对在地下岩层中传播的弹性地震波的相速、能速和时-深转换的影响。结果表明:在关于垂直轴对称的横向各向同性介质非对称轴方向传播的P波的能速可以小于对称轴方向的相速,而在非对称轴方向传播的SV波的能速始终大于或等于对称轴方向的相速;如果不考虑各向异性或考虑各向异性但忽略在地层中传播的地震波的能速和相速之间的差别,会引起对地震波勘探信号的时-深转换产生误差,即不能用地震波勘探信号的走时信息准确地反演地下岩层的地质结构。

Controllable high Curie temperature through 5d transition metal atom doping in CrI_(3)

Two-dimensional(2D) CrI_(3) is a ferromagnetic semiconductor with potential for applications in spintronics. However,its low Curie temperature(T_(c)) hinders realistic applications of CrI3. Based on first-principles calculations, 5d transition metal(TM) atom doping of CrI_(3)(TM@CrI_(3)) is a universally effective way to increase T_(c), which stems from the increased magnetic moment induced by doping with TM atoms. T_(c) of W@CrI_(3) reaches 254 K, nearly six times higher than that of the host CrI_(3). When the doping concentration of W atoms is increased to above 5.9%, W@CrI_(3) shows room-temperature ferromagnetism. Intriguingly, the large magnetic anisotropy energy of W@CrI_(3) can stabilize the long-range ferromagnetic order. Moreover, TM@CrI_(3) has a strong ferromagnetic stability. All TM@CrI_(3) change from a semiconductor to a halfmetal, except doping with Au atom. These results provide information relevant to potential applications of CrI_(3) monolayers in spintronics.

Electronic property and topological phase transition in a graphene/CoBr_(2) heterostructure

Recently,significant experimental advancements in achieving topological phases have been reported in van der Waals(vdW)heterostructures involving graphene.Here,using first-principles calculations,we investigate graphene/CoBr_(2)(Gr/CoBr_(2))heterostructures and find that an enhancement of in-plane magnetic anisotropy(IMA)energy in monolayer CoBr_(2) can be accomplished by reducing the interlayer distance of the vdW heterostructures.In addition,we clarify that the enhancement of IMA energy primarily results from two factors:one is the weakness of the Co-d_(xy) and Co-d_(x^(2)-y^(2)) orbital hybridization and the other is the augmentation of the Co-d_(yz) and Co-d_(z)2 orbital hybridization.Meanwhile,calculation results suggest that the Kosterlitz–Thouless phase transition temperature(TKT)of a 2D XY magnet Gr/CoBr_(2)(23.8 K)is higher than that of a 2D XY monolayer CoBr_(2)(1.35 K).By decreasing the interlayer distances,the proximity effect is more pronounced and band splitting appears.Moreover,by taking into account spin–orbit coupling,a band gap of approximately 14.3 meV and the quantum anomalous Hall effect(QAHE)are attained by decreasing the interlayer distance by 1.0 A.Inspired by the above conclusions,we design a topological field transistor device model.Our results support that the vdW interlayer distance can be used to modulate the IMA energy and QAHE of materials,providing a pathway for the development of new low-power spintronic devices.

Anisotropy of the crystallographic orientation and corrosion performance of high-strength AZ80 Mg alloy

A high-strength AZ80 Mg alloy was prepared through multi-direction forging,thermal extrusion,and peak-aged heat treatment.The microstructure,crystallographic orientation and corrosion performance of extrusion-direction,transverse-direction,and normal-direction specimens were investigated using scanning electron microscopy,electron backscatter diffraction,and atomic force microscopy,respectively.Experimental results showed that crystallographic orientation significantly influenced the corrosion performance of AZ80 Mg alloy.Corrosion rates largely increased with decreased(0001)crystallographic plane intensity,whereas the(10−10)and(2−1−10)crystallographic plane intensities increased.This study showed that the corrosion rates of alloy can be modified to some extent by controlling texture,thereby promoting the applications of high-strength AZ80 Mg alloys in the aerospace and national-defense fields.