Density Functional Theory Study of Metallic Silicon (111) Plane Structures

Chemical Bonding and Activity of Atomically Dispersed Silicon in Two- and Three-Dimensional Materials

On the basis of the especially tunable electronic property of Si, several kinds of nanomaterials with atomically dispersed Si were constructed and characterized by extensive first-principles calculations and ab initio molecular dynamics (AIMD) simulations. The new-type Si(X≡Y)n wide-bandgap semiconductors featuring through-space d-π* hyperconjugation exhibit unique properties in photoelectric conversion, photoconductivity, structural mechanics, etc. The SiC8 siligraphene with the planar tetracoordinate Si (ptSi) has a high lithium-storage capacity and comparably facile surface migration behaviors of both Li and Li+, making it a promising anode material for high-performance Li-ion batteries. The atomically dispersed Si sites of 2D monolayer materials, such as ptSi and three- and four-coordinated Si atoms, generally exhibit remarkable catalytic activity toward CO2 activation with different electron mechanisms, resulting in different scaling relations between the activity and the p-band center. The computational findings enrich the understanding of structural and chemical properties of silicon and open up avenues for developing Si-based functional materials.

Metallic Germanium (111) Slab Structures

Prior research has indicated that the surface electron conductivity of Ge (111) wafers surpasses that of Ge (100) and Ge (110) wafers. This disparity has been ascribed to the variations in bond length, geometry, and frontier orbital electron energy distribution across different surface planes. The ab initio molecular dynamics (AIMD) simulation is used for the thermal stability of the Ge (111) slabs with different thicknesses and has provided new knowledge of its potential applications. To delve deeper into the properties of Ge (111) surfaces, we executed calculations for one- and two-layer Ge (111) surface slabs. The electrical conductivities of these slabs at room temperature were determined to be 966081.89 and 760157.03 Ω^-1 m^-1, respectively, with a unit cell conductivity of 1.96 Ω^-1 m^-1. These findings align with actual experimental data. Notably, the electrical conductivity of the single-layer Ge (111) surface exceeded that of intrinsic Ge by 100,000 times, heralding intriguing potential for including Ge surfaces in future device applications.

Stabile fluoro-benzene-based spacer for lead-free Dion-Jacobson perovskites

Two-dimensional perovskite materials have been investigated as potential candidates for next-generation-wide band gap devices and lead-based perovskites are the most common materials within two-and three-dimensional structures due to their superior optoelectronic properties. Nevertheless, the stability and toxic element issues are the two significant shortcomings of device commercialization. The fluoro-benzene-based divalent ammonium spacer cations and replacing Zn²⁺ with Pb²⁺ will improve the two-dimensional perovskite stability. These stable lead-free wide band gap two-dimensional structures have better carrier mobility at high-temperature regions. Therefore, lead-free two-dimensional perovskites might be suitable for higher temperatures optoelectronic applications.