Chin. Phys. B ›› 2012, Vol. 21 ›› Issue (12): 127103-127103.doi: 10.1088/1674-1056/21/12/127103

• CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES • 上一篇    下一篇

First-principles calculations on the elastic and thermodynamic properties of NbN

任达华, 程新路   

  1. Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
  • 收稿日期:2012-04-12 修回日期:2012-05-16 出版日期:2012-11-01 发布日期:2012-11-01
  • 基金资助:
    Project supported by the National Natural Science Foundation of China (Grant No. 11176020).

First-principles calculations on the elastic and thermodynamic properties of NbN

Ren Da-Hua (任达华), Cheng Xin-Lu (程新路)   

  1. Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
  • Received:2012-04-12 Revised:2012-05-16 Online:2012-11-01 Published:2012-11-01
  • Contact: Cheng Xin-Lu E-mail:chengxl@scu.edu.cn
  • Supported by:
    Project supported by the National Natural Science Foundation of China (Grant No. 11176020).

摘要: The elastic and thermodynamic properties of NbN at high pressures and high temperatures are investigated by the plane-wave pseudopotential density functional theory (DFT). The generalized gradient approximation (GGA) with Perdew-Burke-Ernzerhof (PBE) method is used to describe the exchange-correlation energy in the present work. The calculated equilibrium lattice constant a0, bulk modulus B0, and the pressure derivative of bulk modulus B0' of NbN with rocksalt structure are in good agreement with numerous experimental and theoretical data. The elastic properties over a range of pressures from 0 to 80.4 GPa are obtained. Isotropic wave velocities and anisotropic elasticity of NbN are studied in detail. It is indicated that NbN is highly anisotropic in both longitudinal and shear-wave velocities. According to the quasi-harmonic Debye model, in which the phononic effect is considered, the relations of (V-V0)/V0 to the temperature and the pressure, and the relations of the heat capacity CV and the thermal expansion coefficient α to temperature are discussed in a pressure range from 0 to 80.4 GPa and a temperature range from 0 to 2500 K. At low temperature, CV is proportional to T3 and tends to the Dulong-Petit limit at higher temperature. We predict that the thermal expansion coefficient α of NbN is about 4.20×10-6/K at 300 K and 0 GPa.

关键词: NbN density functional theory, quasi-harmonic Debye model, elastic constants thermodynamic properties

Abstract: The elastic and thermodynamic properties of NbN at high pressures and high temperatures are investigated by the plane-wave pseudopotential density functional theory (DFT). The generalized gradient approximation (GGA) with Perdew-Burke-Ernzerhof (PBE) method is used to describe the exchange-correlation energy in the present work. The calculated equilibrium lattice constant a0, bulk modulus B0, and the pressure derivative of bulk modulus B0' of NbN with rocksalt structure are in good agreement with numerous experimental and theoretical data. The elastic properties over a range of pressures from 0 to 80.4 GPa are obtained. Isotropic wave velocities and anisotropic elasticity of NbN are studied in detail. It is indicated that NbN is highly anisotropic in both longitudinal and shear-wave velocities. According to the quasi-harmonic Debye model, in which the phononic effect is considered, the relations of (V-V0)/V0 to the temperature and the pressure, and the relations of the heat capacity CV and the thermal expansion coefficient α to temperature are discussed in a pressure range from 0 to 80.4 GPa and a temperature range from 0 to 2500 K. At low temperature, CV is proportional to T3 and tends to the Dulong-Petit limit at higher temperature. We predict that the thermal expansion coefficient α of NbN is about 4.20×10-6/K at 300 K and 0 GPa.

Key words: NbN density functional theory, quasi-harmonic Debye model, elastic constants thermodynamic properties

中图分类号:  (Density functional theory, local density approximation, gradient and other corrections)

  • 71.15.Mb
62.20.de (Elastic moduli) 67.25.bd (Thermodynamic properties)