Electronic, optical, and water solubility properties of two-dimensional layered ${\mathrm{SnSi}}_2{\mathrm{N}}_4$ from first principles

In this work, we identify a two-dimensional layered nitridosilicate ${\mathrm{SnSi}}_2{\mathrm{N}}_4$ in hexagonal structure via first-principles calculations. From the total energy calculations, ${\mathrm{SnSi}}_2{\mathrm{N}}_4$ is thermodynamically stable. The dynamic stabilities are demonstrated by the phonon spectrum and molecular-dynamics simulations. The ${\mathrm{SnSi}}_2{\mathrm{N}}_4$ exhibits semiconducting behavior with a direct band gap of 3.70 eV $\left({\mathrm{GW}}_0\right)$, Young's modulus of 478 GPa and breaking strength of 47 GPa, and electron mobility of $2736\mathrm{c}{\mathrm{m}}^2{\mathrm{V}}^{\text{–}1}{\mathrm{s}}^{\text{–}1}$ (Perdew-Burke-Ernzerhof). According to the absorption spectra, ${\mathrm{SnSi}}_2{\mathrm{N}}_4$ presents good absorption of ultraviolet light with high energy. The chemical stability of aqueous solution is verified by the molecular-dynamics simulations.

Figure 1

Crystal structure of hexagonal ${\mathrm{SnSi}}_2{\mathrm{N}}_4$, AIMD simulations, and phonon dispersion. (a) The upper is the top view of the predicted structure, and the lower is the side view. AIMD simulations at (b) 300 K and (c) 1500 K for 10 000 steps (10 ps). The AIMD optimized structures at (d) 300 K and (e) 1500 K. (f) Calculated phonon dispersion curves of ${\mathrm{SnSi}}_2{\mathrm{N}}_4$.

Figure 2

Electronic structure and levels of monolayer ${\mathrm{SnSi}}_2{\mathrm{N}}_4$. Electronic band structure by (a) PBE, (b) HSE06, and (c) ${\mathrm{GW}}_0$.

Figure 3

The optical absorption of ${\mathrm{SnSi}}_2{\mathrm{N}}_4$.

Figure 4

The stability of aqueous solution and schematic diagrams of H, O and ${\mathrm{H}}_2\mathrm{O}$ adsorbed on ${\mathrm{SnSi}}_2{\mathrm{N}}_4$. The structures of ${\mathrm{SnSi}}_2{\mathrm{N}}_4$ with nine molecules of water (a) before and (b) after AIMD simulations at 300 K for 5 ps. (c) MSDs for Sn, Si, N, H, and O atoms from AIMD simulations at 300 K for 5 ps. (d) Site I. (e) Site II. (f) Site III. (g)–(i) The absorption of H, O, and ${\mathrm{H}}_2\mathrm{O}$ on ${\mathrm{SnSi}}_2{\mathrm{N}}_4$. The white and red spheres represent the H and O atoms, respectively.