Comparative study on structural, elastic, dynamical, and thermodynamic properties of Weyl semimetals MX (M = Ta or Nb; X = As or P). (September 2017)

• Record Type: Journal Article
• Authors: Liu, Lei; Wang, Zhao-Qi; Hu, Cui-E.; Cheng, Yan; Ji, Guang-Fu
• Is Part Of: Solid state communications. Volume 263(2017)
• Page Start: 10
• Page End: 18
• Publication Date: 2017-09
• Subjects: Weyl semimetal -- Elastic constants -- Lattice dynamics -- Thermodynamic properties -- Density functional theory; Solid state chemistry -- Periodicals; Solid state physics -- Periodicals; Chimie de l'état solide -- Périodiques; Physique de l'état solide -- Périodiques; 530.41
• DOI: 10.1016/j.ssc.2017.06.011
• Languages: English
• ISSNs: 0038-1098

Abstract

Abstract: We present a comparative investigation on structural, elastic, dynamical and thermodynamic properties of Weyl semimetals MX ( M = Ta or Nb; X = As or P) using density functional theory (DFT) within the generalized gradient approximation. The elastic properties of NbAs, TaP and NbP are obtained for the first time, then we compared them with each other and with some well-studied materials. Among four Weyl semimetals, TaP and NbAs possess the largest and smallest bulk modulus B, shear modulus G, and Young's modulus E, respectively, while NbP and TaAs own the maximum and minimum elastic Debye temperature. Through the analysis of three dimensional (3D) representations and two dimensional (2D) projections of Young's modulus, MX series exhibit distinct elastic anisotropy, especially for TaAs and NbAs. The calculated phonon dispersions of four Weyl semimetals show no imaginary frequency throughout the Brillouin zone, indicating they are dynamically stable. In addition, compared with other theoretical results, our calculated Brillouin-zone-center frequencies of MX series are more in line with experimental data. Furthermore, Phonon velocities are obtained using phonon spectra, and anisotropic phonon group velocities are responsible for their anisotropic lattice thermal conductivity. Additionally, thermodynamic properties are also predicted using the calculated phonon density of states. The results are in good agreement with available experimental values. We expect our work can provide more information for further experimental studies. Highlights: The calculated elastic properties for NbAs, TaP and NbP are obtained for the first time. MX ( M = Ta or Nb; X = As or P) exhibit distinct elastic anisotropy, especially for TaAs and NbAs. Their phonon frequencies at gamma point, main atomic displacement patterns, phonon velocities, and thermodynamic properties are also presented.