Hydrostatic pressure provides an efficient way to tune and optimize the properties of solid materials without changing their composition. In this work, we investigate the electronic, optical, and mechanical properties of antiperovskite X₃NP (X²⁺ = Ca, Mg) upon compression by first-principles calculations. Our results reveal that the system is anisotropic, and the lattice constant a of X₃NP exhibits the fastest rate of decrease upon compression among the three directions, which is different from the typical Pnma phase of halide and chalcogenide perovskites. Meanwhile, Ca₃NP has higher compressibility than Mg₃NP due to its small bulk modulus. The electronic and optical properties of Mg₃NP show small fluctuations upon compression, but those of Ca₃NP are more sensitive to pressure due to its higher compressibility and lower unoccupied 3d orbital energy. For example, the band gap, lattice dielectric constant, and exciton binding energy of Ca₃NP decrease rapidly as the pressure increases. In addition, the increase in pressure significantly improves the optical absorption and theoretical conversion efficiency of Ca₃NP. Finally, the mechanical properties of X₃NP are also increased upon compression due to the reduction in bond length, while inducing a brittle-to-ductile transition. Our research provides theoretical guidance and insights for future experimental tuning of the physical properties of antiperovskite semiconductors by pressure.

SiO₂通常以三维晶体或无定形结构存在，限制了其在新技术如新一代集成电路中的应用，因此二维SiO₂的研究引起了越来越多的关注。本文通过删除三维层状CaAl₂Si₂O₈结构中的Ca和Al原子，直接构建出新的二维SiO₂构型。采用基于密度泛函理论的第一性原理计算，结构优化获得的新型2D SiO₂具有P-62m对称性，群号189。通过结合能、弹性系数、分子动力学模拟和声子谱计算，发现新型2D SiO₂具有高机械稳定性、热力学稳定性和动力学稳定性。电子性质和光学性质计算发现，2D SiO₂是带隙为6.08 eV绝缘体，且具有良好的光透射率和光导率。此外，通过研究面内双轴应变对2D SiO₂电子和光学性质的影响，发现2D SiO₂的带隙和介电函数受面内拉伸应变的影响较压缩应变略大，不过其整体光学性质受应变影响不大，保证了其在实际应用中电子性质和光学性质的稳定性。

由低维InAs材料和其他二维层状材料堆叠而成的垂直范德华异质结构在纳米电子、光电子和量子信息等新兴领域中应用广泛。探索跨结界面的电荷转移机制对于全面理解该类器件的非凡特性至关重要。第一性原理计算在揭示界面电荷转移特性与各种能量稳定型InAs基范德华异质结的电、光、磁等原理物理特性和器件性能变化之间的内在关系方面发挥着不可比拟的作用。文中梳理、总结和探讨了近年来InAs基范德华异质结间界面电荷转移特性的理论研究工作与潜在的功能应用，提出在理论方法和计算精度方面大力发展第一性原理计算的几个途径，为更好地开展InAs基范德华异质结的基础科学研究和应用器件设计提供可借鉴的量化研究基础。

Inspired by the recently predicted 2D MX₂Y₆ (M = metal element; X = Si/Ge/Sn; Y = S/Se/Te), we explore the possible applications of alkaline earth metal (using magnesium as example) in this family based on the idea of element replacement and valence electron balance. Herein, we report a new family of 2D quaternary compounds, namely MgMX₂Y₆ (M = Ti/Zr/Hf; X = Si/Ge; Y = S/Se/Te) monolayers, with superior kinetic, thermodynamic and mechanical stability. In addition, our results indicate that MgMX₂Y₆ monolayers are all indirect band gap semiconductors with band gap values ranging from 0.870 to 2.500 eV. Moreover, the band edges and optical properties of 2D MgMX₂Y₆ are suitable for constructing multifunctional optoelectronic devices. Furthermore, for comparison, the mechanical, electronic and optical properties of In₂X₂Y₆ monolayers have been discussed in detail. The success of introducing Mg into the 2D MX₂Y₆ family indicates that more potential materials, such as Ca- and Sr-based 2D MX₂Y₆ monolayers, may be discovered in the future. Therefore, this work not only broadens the existing family of 2D semiconductors, but it also provides beneficial results for the future.Inspired by the recently predicted 2D MX₂Y₆ (M = metal element; X = Si/Ge/Sn; Y = S/Se/Te), we explore the possible applications of alkaline earth metal (using magnesium as example) in this family based on the idea of element replacement and valence electron balance. Herein, we report a new family of 2D quaternary compounds, namely MgMX₂Y₆ (M = Ti/Zr/Hf; X = Si/Ge; Y = S/Se/Te) monolayers, with superior kinetic, thermodynamic and mechanical stability. In addition, our results indicate that MgMX₂Y₆ monolayers are all indirect band gap semiconductors with band gap values ranging from 0.870 to 2.500 eV. Moreover, the band edges and optical properties of 2D MgMX₂Y₆ are suitable for constructing multifunctional optoelectronic devices. Furthermore, for comparison, the mechanical, electronic and optical properties of In₂X₂Y₆ monolayers have been discussed in detail. The success of introducing Mg into the 2D MX₂Y₆ family indicates that more potential materials, such as Ca- and Sr-based 2D MX₂Y₆ monolayers, may be discovered in the future. Therefore, this work not only broadens the existing family of 2D semiconductors, but it also provides beneficial results for the future.