Phase Transition and Elastic Properties of NbN under Hydrostatic Pressure

• Published in: Journal of Wuhan University of Technology. Materials science edition Vol. 29; no. 1; pp. 49 - 57
• Main Authors: Ren, Dahua, An, Xinyou, Cheng, Xinlu, Luo, Xuan, Yang, Ruizhuang, Zahng, Zhen, Wu, Weidong
• Format: Journal Article
• Language: English
• Published: Heidelberg Wuhan University of Technology 01.02.2014; Springer Nature B.V
• Subjects: Advanced Materials; Bulk modulus; Chemistry and Materials Science; Collapse; Debye temperature; Derivatives; Elastic constants; Materials Science; Mathematical analysis; NbN; Niobium nitride; Phase transformations; 体积模量; 各向异性弹性; 弹性常数; 弹性性能; 横波速度; 相变; 静水压力; anisotropic elasticity; isotropic wave velocity; phase transition; NbN; elastic properties
• ISSN: 1000-2413; 1993-0437
• DOI: 10.1007/s11595-014-0866-y

First-principles pseudopotential calculations are performed to investigate the phase transition and elastic properties of niobium nitrides （NbN）. The lattice parameters a0 and c0/a0, elastic constants Cu, bulk modulus B0, and the pressure derivative of bulk modulus B0＇ are calculated. The results are in good agreement with numerous experimental and theoretical data. The enthalpy calculations predict that NbN undergoes phase transition from NaCl-type to NiAs-type structure at 13.4 GPa with a volume collapse of about 4.0% and from AsNi-type to CW-type structure at 26.5 GPa with a volume collapse of about 7.0%. Among the four types of structures, CW-type is the most stable structure. The elastic properties are analyzed on the basis of the calculated elastic constants. Isotropic wave velocities and anisotropic elasticity of NbN are studied in detail. The longitudinal and shear-wave velocities, Vr, Vs and V increase with increasing pressure, respectively. The Debye temperature OD increases monotonically with increasing pressure except for NiAs-type structure. Both the longitudinal velocity and the shear-wave velocity increase with pressure for wave vector along all the propagation directions, except for VTA（[100]） and VTA[001]（[110]） with NaCl structure and VTA[001]（[100]） with the other three types of structures.