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Theoretical Study on the High-Temperature P6 and P6' Phases of Si3N4: A Tool to Aid in Ceramics Development
Ben-hai Yu,Dong Chen*
Author NameAffiliationE-mail
Ben-hai Yu College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, China  
Dong Chen* College of Physics and Electronic Engineering, Xinyang Normal University, Xinyang 464000, China chchendong2010@163.com 
Abstract:
Atomistic modeling based on the density functional theory combined with the quasi-harmonic approximation is used to investigate the lattice parameters and elastic moduli of the P6 and P6' phases of Si3N4. β-Si3N4 is set as a benchmark system since accurate experiments are available. The calculated lattice constants and elastic constants of β-Si3N4 are in good agreement with the experimental data. The crystal anisotropy, mechanical stability, and brittle behavior of P6- and P6'-Si3N4 are also discussed in the pressure range of 30-55 GPa. The results show that these two polymorphs are metallic compounds. The brittleness and elastic anisotropy increase with applied pressure increasing. Besides, the phase boundaries of the β→P6'→δ transitions are also analysed. The β phase is predicted to undergo a phase transition to the P6' phase at 40.0 GPa and 300 K. Upon further compression, the P6'→δ transition can be observed at 53.2 GPa. The thermal and pressure effects on the heat capacity, cell volume and bulk modulus are also determined. Some interesting features are found at high temperatures.
Key words:  First-principles, Nitrides, Brittleness, Phase diagram
FundProject:
氮化硅新相P6和P6'的理论研究:一种研究陶瓷材料的新工具
余本海,陈东*
摘要:
在原子尺度上构建模型,采用密度泛函理论结合准谐波近似研究了氮化硅新相(P6和P6'相)的点阵常数、弹性常数和弹性模量. 并使用β-Si3N4作基准材料来测试计算结果的准确性. 研究发现β-Si3N4的晶胞常数和弹性常数与实验值吻合相当好. 研究了P6和P6'相在30~55 GPa的各向异性因子、脆性和力学稳定性,结果表明两相属于金属性和脆性材料,且晶体的脆性和各向异性都随着压强的升高而增大. β相在40 GPa和300 K时会转变成P6'相. 当压强继续升高到5
关键词:  第一性原理,氮化物,脆性,相图
DOI:10.1063/1674-0068/27/01/103-108
分类号: