WikiEdge:ArXiv速递/2025-03-03

摘要

• 原文标题：Investigation of O interstitial diffusion in $β$-Ga$_2$O$_3$: direct approach via master diffusion equations
• 中文标题：$β$-Ga$_2$O$_3$中氧间隙扩散的研究：通过主扩散方程的直接方法
• 发布日期：2025-03-03 16:54:55+00:00
• 作者：Grace McKnight, Channyung Lee, Elif Ertekin
• 分类：cond-mat.mtrl-sci, physics.app-ph, physics.comp-ph
• 原文链接：http://arxiv.org/abs/2503.01735v1

中文摘要：单斜晶系的$\beta$-Ga$_2$O$_3$是一种有前景的宽带隙半导体材料，由于其低对称性的晶体结构，表现出复杂的各向异性扩散特性和质量传输行为。通过第一性原理计算结合主扩散方程，我们确定了中性氧间隙（$\text{O}_{\text{i}}^{0}$）和带2-电荷的氧间隙（$\text{O}_{\text{i}}^{2-}$）的三维扩散张量。通过对构型空间的系统探索，我们识别了这两种主要电荷态的稳定构型及其相应的形成能。通过考虑间隙或间隙跳跃，连接每一对低能构型，我们构建了三维扩散网络，并评估了网络中所有过渡路径的跳跃势垒。结合（i）缺陷构型及其形成能和（ii）连接它们的跳跃势垒，我们通过Onsager方法分别构建并求解了$\text{O}_{\text{i}}^{0}$和$\text{O}_{\text{i}}^{2-}$的主扩散方程，得到了相应的三维扩散张量D$_{\text{O}_{\text{i}}}^{0}$和D$_{\text{O}_{\text{i}}}^{2-}$。$\text{O}_{\text{i}}^{0}$和$\text{O}_{\text{i}}^{2-}$都表现出沿$b$轴的最快扩散，显示出显著的各向异性。沿[100]和[$\overline{2}01$]方向预测的自扩散系数与之前报道的同位素标记氧示踪实验值吻合良好，突出了该方法在捕捉复杂扩散机制方面的可靠性。

摘要

• 原文标题：Fire danger likely overestimated in future climate projections
• 中文标题：未来气候预测中火灾危险可能被高估
• 发布日期：2025-03-03 18:42:50+00:00
• 作者：Aurora Matteo, Ginés Garnés-Morales, Alberto Moreno, Ribeiro Andreia, César Azorín-Molina, Joaquín Bedia, Francesca Di Giuseppe, Robert J. H. Dunn, Sixto Herrera, Antonello Provenzale, Yann Quilcaille, Miguel Ángel Torres Vázquez, Marco Turco
• 分类：physics.ao-ph
• 原文链接：http://arxiv.org/abs/2503.01818v1

原文摘要：The Canadian Fire Weather Index (FWI) is widely used to assess wildfire danger and relies on meteorological data at local noon. However, climate models often provide only daily aggregated data, which poses a challenge for accurate FWI calculations in climate change studies. Here, we examine how using daily approximations for FWI95d -- the annual count of extreme fire weather days exceeding the 95th percentile of local daily FWI values -- compares to the standard noon-based approach for the period 1980--2023. Our findings reveal that FWI95d calculated with noon-specific data increased globally by approximately 65\%, corresponding to 11.66 additional extreme fire weather days over 44 years. In contrast, daily approximations tend to overestimate these trends by 5--10\%, with combinations involving minimum relative humidity showing the largest divergences. Globally, up to 15 million km$^2$, particularly in the western United States, southern Africa, and parts of Asia, exhibit significant overestimations. Among our daily approximation methods, the least biased proxy is the one that uses daily mean data for all variables. We recommend (i) prioritizing the inclusion of sub-daily meteorological data in future climate model intercomparison projects to enhance FWI accuracy, and (ii) adopting daily mean approximations as the least-biased alternative if noon-specific data are unavailable. 中文摘要：加拿大火灾天气指数（FWI）被广泛用于评估野火风险，并依赖于当地中午的气象数据。然而，气候模型通常仅提供每日汇总数据，这为气候变化研究中的准确FWI计算带来了挑战。本文研究了在1980年至2023年期间，使用每日近似值计算FWI95d（即超过当地每日FWI值第95百分位数的极端火灾天气日数的年计数）与标准基于中午的方法的比较。 我们的研究结果表明，使用中午特定数据计算的FWI95d在全球范围内增加了约65%，相当于44年内增加了11.66个极端火灾天气日。相比之下，每日近似值往往会高估这些趋势5-10%，其中涉及最低相对湿度的组合显示出最大的差异。在全球范围内，多达1500万平方公里的地区，特别是美国西部、南部非洲和亚洲部分地区，显示出显著的高估。在我们的每日近似方法中，偏差最小的代理是使用所有变量的每日平均值的方法。 我们建议：（i）在未来的气候模型比较项目中优先纳入次每日气象数据，以提高FWI的准确性；（ii）如果无法获得中午特定数据，则采用每日平均值近似作为偏差最小的替代方案。

摘要

• 原文标题：A COMSOL framework for predicting hydrogen embrittlement -- Part II: phase field fracture
• 中文标题：用于预测氢脆的COMSOL框架——第二部分：相场断裂
• 发布日期：2025-03-03 17:39:02+00:00
• 作者：A. Díaz, J. M. Alegre, I. I. Cuesta, E. Martínez-Pañeda
• 分类：cs.CE, physics.app-ph, physics.chem-ph
• 原文链接：http://arxiv.org/abs/2503.01765v1

原文摘要：Prediction of hydrogen embrittlement requires a robust modelling approach and this will foster the safe adoption of hydrogen as a clean energy vector. A generalised computational model for hydrogen embrittlement is here presented, based on a phase field description of fracture. In combination with Part I of this work, which describes the process of hydrogen uptake and transport, this allows simulating a wide range of hydrogen transport and embrittlement phenomena. The material toughness is defined as a function of the hydrogen content and both elastic and elastic-plastic material behaviour are incorporated, enabling to capture both ductile and brittle fractures, and the transition from one to the other. The accumulation of hydrogen near a crack tip and subsequent embrittlement is numerically evaluated in a single-edge cracked plate, a boundary layer model and a 3D vessel case study, demonstrating the potential of the framework. Emphasis is placed on the numerical implementation, which is carried out in the finite element package COMSOL Multiphysics, and the models are made freely available. 中文摘要：预测氢脆需要一种稳健的建模方法，这将促进氢作为清洁能源载体的安全采用。本文提出了一种基于断裂相场描述的氢脆通用计算模型。结合本工作的第一部分，该部分描述了氢的吸收和传输过程，这使得模拟广泛的氢传输和氢脆现象成为可能。材料韧性被定义为氢含量的函数，并且结合了弹性和弹塑性材料行为，从而能够捕捉到韧性断裂和脆性断裂以及两者之间的转变。在单边裂纹板、边界层模型和三维容器案例研究中，数值评估了裂纹尖端附近氢的积累和随后的氢脆，展示了该框架的潜力。重点放在数值实现上，该实现是在有限元软件COMSOL Multiphysics中进行的，并且模型是免费提供的。