Graphene-based analogs and derivatives provide numerous routes to achieve unconventional properties and potential applications. Particularly, two-dimensional (2D) binary materials of group-IV elements are drawing increasing interest. In this work, we proposed the design of three 2D graphene-based materials, namely, XC₆-enes (X = Ge, Sn, or Pb), based on first-principles calculations. These new materials possess intriguing properties superior to graphene, such as biaxial negative Poisson's ratio (NPR), moderate bandgap, and high carrier mobility. These XC₆-enes comprise sp² carbon and sp³ X (X = Ge, Sn, Pb) atoms with hexagonal and pentagonal units by doping graphene with X atoms. The stability and plausibility of these 2D materials are verified from formation energies, phonon spectra, ab initio molecular dynamic simulations, and elastic constants. The incorporation of X atoms leads to highly anisotropic mechanical properties along with NPR due to the unique tetrahedral structure and hat-shaped configuration. In the equilibrium state, all the XC₆-enes are moderate-band-gap semiconductors. The carrier mobilities of the XC₆-enes were highly anisotropic (∼10⁴ cm⁻² V⁻¹ s⁻¹ along the [010]-direction). Such outstanding properties make the 2D frameworks promising for application in novel electronic and micromechanical devices.

中文翻译：

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具有中等带隙、双轴负泊松比和高载流子迁移率的二维 XC6-烯（X = Ge、Sn、Pb）

基于石墨烯的类似物和衍生物提供了多种途径来实现非常规特性和潜在应用。特别是，IV 族元素的二维 (2D) 二元材料引起了越来越多的关注。在这项工作中，我们基于第一性原理计算提出了三种基于二维石墨烯的材料的设计，即 XC ₆烯（X = Ge、Sn 或 Pb）。这些新材料具有优于石墨烯的有趣特性，例如双轴负泊松比 (NPR)、中等带隙和高载流子迁移率。这些 XC ₆ -enes 包含 sp ²碳和 sp ³通过用 X 原子掺杂石墨烯，X (X = Ge, Sn, Pb) 原子具有六边形和五边形单元。这些二维材料的稳定性和合理性通过形成能、声子光谱、从头算分子动力学模拟和弹性常数得到验证。由于独特的四面体结构和帽形构型，X 原子的掺入导致高度各向异性的机械性能以及 NPR。在平衡状态下，所有的 XC ₆烯都是中等带隙半导体。XC _{6 -}烯的载流子迁移率是高度各向异性的（~10 ⁴ cm ^-2 V ^-1 s ^-1沿 [010] 方向）。如此出色的特性使二维框架有望应用于新型电子和微机械设备。