Prediction of novel hard phases of Si{sub 3}N{sub 4}: First-principles calculations

Journal Article · Sat Aug 15 00:00:00 EDT 2015 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/J.JSSC.2015.04.002· OSTI ID:22486716

Cui, Lin; Hu, Meng; Wang, Qianqian; Xu, Bo; Yu, Dongli; Liu, Zhongyuan; He, Julong

Exploration of novel hard metastable phases of silicon nitride was performed using a recently developed particle-swarm optimization method within the CALYPSO software package. Three potential hard metastable phases of t-Si{sub 3}N{sub 4}, m-Si{sub 3}N{sub 4}, and o-Si{sub 3}N{sub 4} were predicted. These phases are mechanically and dynamically stable at ambient pressure based on their elastic constants and phonon dispersions. t-Si{sub 3}N{sub 4} and m-Si{sub 3}N{sub 4} exhibit lower energies than γ-Si{sub 3}N{sub 4} at pressures below 2.5 GPa and 2.9 GPa, respectively, which promise that the formers could be obtained by quenching from γ-Si{sub 3}N{sub 4}. o-Si{sub 3}N{sub 4} is a better high-pressure metastable phase than CaTi{sub 2}O{sub 4}-type Si{sub 3}N{sub 4} proposed by Tatsumi et al. and it can come from the transition of γ-Si{sub 3}N{sub 4} under 198 GPa. The theoretical band gaps of t-Si{sub 3}N{sub 4}, m-Si{sub 3}N{sub 4}, and o-Si{sub 3}N{sub 4} at ambient pressure were 3.15 eV, 3.90 eV, and 3.36 eV, respectively. At ambient pressure, the Vickers hardness values of t-Si{sub 3}N{sub 4} (32.6 GPa), m-Si{sub 3}N{sub 4} (31.5 GPa), and o-Si{sub 3}N{sub 4} (36.1 GPa) are comparable to β-Si{sub 3}N{sub 4} and γ-Si{sub 3}N{sub 4}. With the pressure increasing, t-Si{sub 3}N{sub 4}, m-Si{sub 3}N{sub 4}, and o-Si{sub 3}N{sub 4} will change from the brittle to ductile state at about 15.7 GPa, 7.3 GPa and 28.9 GPa, respectively. - Graphical abstract: This figure shows the crystal structures of three Si{sub 3}N{sub 4} predicted in this manuscript, and left to right: t-Si{sub 3}N{sub 4}, m-Si{sub 3}N{sub 4} and o-Si{sub 3}N{sub 4}. - Highlights: • We explored three metastable phases of Si{sub 3}N{sub 4} — t-Si{sub 3}N{sub 4}, m-Si{sub 3}N{sub 4}, and o-Si{sub 3}N{sub 4}. • The enthalpies of t and m- are much lower than that of γ at ambient pressure. • ois one further high pressure phase than γ. • o-Si{sub 3}N{sub 4} is the most hardest phase in Si{sub 3}N4 system. • Increasing pressure will change them from brittle to ductile state.

• OSTI ID: 22486716
• Journal Information: Journal of Solid State Chemistry, Vol. 228; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
BRITTLE-DUCTILE TRANSITIONS
COMPARATIVE EVALUATIONS
COMPUTERIZED SIMULATION
CRYSTAL STRUCTURE
ENERGY GAP
ENTHALPY
PARTICLES
PHASE STABILITY
PHASE STUDIES
PHASE TRANSFORMATIONS
PHONONS
PRESSURE DEPENDENCE
QUENCHING
SILICON NITRIDES
VICKERS HARDNESS