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Structural, Mechanical, and Electronic Properties of High-Hardness Silicon Tetranitride

Lulu Liu,Jiacheng Qi,Chi Ding,Dinghui Wang,Shoutao Zhang

Published 2025 in Molecules

ABSTRACT

Materials with high hardness are critical for industrial and aerospace applications, prompting the search for novel compounds with robust covalent networks. Using a first-principles structure prediction method, we systematically explored the phase stability of Si–N compounds under high pressure. We identified two thermodynamically stable phases: Si6N with P-1 symmetry and SiN4 with space group R-3c. Phonon spectra and ab initio molecular dynamics simulations confirm the dynamical and thermal stability of R-3c SiN4 at ambient pressure and up to 2000 K. Notably, R-3c SiN4 exhibits exceptional mechanical properties with a Vickers hardness of 31 GPa, a bulk modulus of 259.53 GPa, and a Young’s modulus of 485.38 GPa. Furthermore, SiN4 possesses a high energy density (1.1 kJ·g−1) and outstanding detonation pressure and velocity (228 kbar, 7.11 km·s−1), both exceeding those of TNT, making it a potential high-energy-density materials. In addition, electronic structure analysis reveals SiN4 has a band gap of 2.5 eV, confirming its nonmetallic characteristics and strongly covalent nature. These findings provide theoretical guidance for the future synthesis of Si–N phases and establish a foundation for designing novel materials that combine high hardness with high-energy density performance.

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