发表机构
University of Dhaka; Florida State University（达卡大学; 佛罗里达州立大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过第一性原理计算，全面揭示了拓扑狄拉克半金属Na3Bi的结构、力学、热学、电子和光学性质，发现其具有脆性共价键、低硬度、低德拜温度、半金属性及高紫外吸收，为相关应用提供了基线。
AI 中文摘要
在过去的几十年里，探索拓扑材料的性质一直是凝聚态物理中一个活跃的研究领域。在此，我们利用密度泛函理论，对最早发现的拓扑狄拉克半金属之一Na3Bi的结构、弹性力学、热学、电子和光学性质进行了第一性原理研究。研究发现，Na3Bi的六方相在力学和动力学上都是稳定的，表现出适度的弹性各向异性，其通用各向异性指数为0.832。该化合物显示出2.386的适中可加工性指数，同时具有2.005的低硬度值，这与其主要为脆性、共价键合的特征一致，并伴有轻微的金属性贡献。其相对较低的德拜温度181.39K表明其晶格力学上较软，原子结合松散。电子结构计算证实了其半金属行为，在费米能级处存在明确的狄拉克点，费米表面由点状口袋组成。在宽光谱范围内的光学分析揭示了非选择性、中等反射率（40%至45%），在可见光区域，折射率异常高，介于2至4.5之间。此外，Na3Bi被发现是紫外辐射的有效吸收体。总之，这些发现为六方Na3Bi的力学、热学和光学行为建立了全面的基线，并指出了其在声学阻尼、紫外传感和光电应用方面的潜在相关性。
英文摘要
Exploring the properties of topological materials has remained an active area of research in condensed matter physics for the past few decades. Here, we present a first-principles investigation of the structural, elasto-mechanical, thermal, electronic, and optical properties of Na3Bi, one of the earliest discovered topological Dirac semimetals, using density functional theory. The hexagonal phase of Na3Bi is found to be both mechanically and dynamically stable, exhibiting moderate elastic anisotropy with a universal anisotropy index of 0.832. The compound displays a moderate machinability index of 2.386 alongside a low hardness value of 2.005, consistent with its predominantly brittle, covalently bonded character accompanied by a slight metallic contribution. Its comparatively low Debye temperature of 181.39K points to a mechanically soft lattice with loosely bound atoms. Electronic structure calculations confirm semimetallic behavior, with well-defined Dirac points pinned at the Fermi level and a Fermi surface composed of point-like pockets. Optical analysis across a wide spectral range reveals non-selective, moderate reflectivity of 40 to 45% and, in the visible region, an unusually high refractive index reaching between 2 and 4.5. Na3Bi is additionally found to be an efficient absorber of ultraviolet radiation. Together, these findings establish a comprehensive baseline for the mechanical, thermal, and optical behavior of hexagonal Na3Bi and point to its potential relevance for acoustic damping, UV-sensing, and optoelectronic applications
