Hou Yinlong, Ren Kai, Wei Yu, Yang Dan, Cui Zhen, Wang Ke
School of Automation, Xi'an University of Posts & Telecommunications, Xi'an 710121, China.
School of Mechanical and Electronic Engineering, Nanjing Forestry University, Nanjing 210042, China.
Molecules. 2023 Sep 8;28(18):6514. doi: 10.3390/molecules28186514.
In recent years, the two-dimensional (2D) orthorhombic SiP flake has been peeled off successfully by micromechanical exfoliation and it exhibits an excellent performance in photodetection. In this paper, we investigated the mechanical properties and the origin of its anisotropy in an orthorhombic SiP monolayer through first-principles calculations, which can provide a theoretical basis for utilizing and tailoring the physical properties of a 2D orthorhombic SiP in the future. We found that the Young's modulus is up to 113.36 N/m along the direction, while the smallest value is only 17.46 N/m in the direction. The in-plane anisotropic ratio is calculated as 6.49, while a similar anisotropic ratio (~6.55) can also be observed in Poisson's ratio. Meanwhile, the in-plane anisotropic ratio for the fracture stress of the orthorhombic SiP monolayer is up to 9.2. These in-plane anisotropic ratios are much larger than in black phosphorus, ReS, and biphenylene. To explain the origin of strong in-plane anisotropy, the interatomic force constants were obtained using the finite-displacement method. It was found that the maximum of interatomic force constant along the direction is 5.79 times of that in the direction, which should be considered as the main origin of the in-plane anisotropy in the orthorhombic SiP monolayer. In addition, we also found some negative Poisson's ratios in certain specific orientations, allowing the orthorhombic SiP monolayer to be applied in next-generation nanomechanics and nanoelectronics.
近年来，二维（2D）正交相SiP薄片已通过微机械剥离成功剥离，并且在光电探测方面表现出优异的性能。在本文中，我们通过第一性原理计算研究了正交相SiP单层的力学性能及其各向异性的起源，这可为未来利用和定制二维正交相SiP的物理性能提供理论基础。我们发现，沿 方向的杨氏模量高达113.36 N/m，而沿 方向的最小值仅为17.46 N/m。面内各向异性比计算为6.49，同时在泊松比中也可观察到类似的各向异性比（~6.55）。同时，正交相SiP单层断裂应力的面内各向异性比高达9.2。这些面内各向异性比远大于黑磷、ReS和联苯中的各向异性比。为了解释强面内各向异性的起源，使用有限位移法获得了原子间力常数。发现沿 方向的原子间力常数最大值是沿 方向的5.79倍，这应被视为正交相SiP单层面内各向异性的主要起源。此外，我们还在某些特定取向中发现了一些负泊松比，这使得正交相SiP单层可应用于下一代纳米力学和纳米电子学。
