Theoretical Study on the High-Temperature P6 and P6＇ Phases of Si3N4： A Tool to Aid in Ceramics Development  

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

作　　者：余本海[1] 陈东[1] 

机构地区：[1]信阳师范学院物理电子工程学院,信阳464000

出　　处：《Chinese Journal of Chemical Physics》2014年第1期103-108,I0004,共7页化学物理学报（英文）

基　　金：ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China （No.U1204501, No.11105115, and No.11304141）, the Project of Basic and Advanced Technology of Henan Province of China （No.112300410021）, and the Key Project of Henan Ed- ucational Committee （No.12A140010）. The authors are grateful to Prof. M. A. Blanco from the Departamento de Qufmica Ffsicay Analitica, Faculatad de Qufmica, Universidad de Oviedo for the Gibbs code.

摘　　要：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.

关 键 词：FIRST-PRINCIPLES Nitrides BRITTLENESS Phase diagram 

分 类 号：O6[理学—化学]