Phase transition and elastic properties of NbN under hydrostatic pressure

作者：Ren Dahua; An Xinyou; Cheng Xinlu^*; Luo Xuan; Yang Ruizhuang; Zahng Zhen; Wu Weidong

来源：Journal of Wuhan University of Technology-Materials Science Edition, 2014, 29(1): 49-57.

DOI：10.1007/s11595-014-0866-y

• phase transition
• elastic properties
• isotropic wave velocity
• anisotropic elasticity
• NbN

First-principles pseudopotential calculations are performed to investigate the phase transition and elastic properties of niobium nitrides (NbN). The lattice parameters a (0) and c (0)/a (0), elastic constants C (ij) , bulk modulus B (0), and the pressure derivative of bulk modulus B (0)' 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, V (P), V (S) and V (m) increase with increasing pressure, respectively. The Debye temperature I similar to (D) 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 V (TA) ([100]) and V (TA[001])([110]) with NaCl structure and V (TA[010])([100]) with the other three types of structures.

• 出版日期2014-2
• 单位中国工程物理研究院; 四川大学