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. 2024 Jun 25;10(13):e33613.
doi: 10.1016/j.heliyon.2024.e33613. eCollection 2024 Jul 15.

Ab-initio insights into the mechanical, phonon, bonding, electronic, optical and thermal properties of hexagonal W2N3 for prospective applications

Istiak Ahmed  1 , F Parvin  1 , R S Islam  1 , S H Naqib  1
Affiliations

Ab-initio insights into the mechanical, phonon, bonding, electronic, optical and thermal properties of hexagonal W2N3 for prospective applications

Istiak Ahmed et al. Heliyon. .

Abstract

We thoroughly investigated the structural, mechanical, electronic, vibrational, optical, thermodynamic, and a number of thermophysical properties of W2N3 compound through first-principles calculations using the DFT based formalism. The calculated structural parameters show very good agreement with the available theoretical and experimental results. The mechanical and dynamical stabilities of this compound have been investigated theoretically from the elastic constants and phonon dispersion curves. The Pugh's and Poisson's ratios of W2N3 are located quite close to the brittle/ductile borderline. W2N3 is elastically anisotropic. The calculated electronic band structure and density of states reveal that W2N3 is conducting in nature. The Fermi surface topology has also been explored. The analysis of charge density distribution map shows that W atoms have comparatively high electron density around compared to the N atoms. Presence of covalent bondings between W-N, W-W, and N-N atoms are anticipated. High melting temperature and high phonon thermal conductivity of W2N3 imply that the compound has potential to be used as a heat sink system. The optical characteristics show anisotropy. The compound can be used in optoelectronic devices due to its high absorption coefficient and low reflectivity in the visible to ultraviolet spectrum. Furthermore, the quasi-harmonic Debye model is used to examine temperature and pressure dependent thermal characteristics of W2N3 for the first time.

Keywords: Density functional theory; Mechanical properties; Optoelectronic properties; Phonon dynamics; Thermal properties; Tungsten nitride.

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Conflict of interest statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Figures

Fig. 1
Fig. 1
(a) Conventional unit cell of W2N3 and (b) its 2D view in the xy-plane.
Fig. 2
Fig. 2
Direction-dependence of Young's modulus (Y), compressibility (β), shear modulus (G), and Poisson's ratio (ν) of W2N3 single crystal.
Fig. 3
Fig. 3
The phonon dispersion spectra (PDS) and phonon density of states (PHDOS) of W2N3.
Fig. 4
Fig. 4
Charge density distribution maps of W2N3 in (a) (111) and (b) (011) plane.
Fig. 5
Fig. 5
Temperature and pressure dependent variations of specific heat capacities Cp and Cv of W2N3.
Fig. 6
Fig. 6
Temperature and pressure dependent variations of entropy, S, of W2N3.
Fig. 7
Fig. 7
Electronic band structure of W2N3 along high symmetry directions in the Brillouin zone. The colored bands (numbered 41–44) cross the Fermi level.
Fig. 8
Fig. 8
Total and partial electronic density of states of W2N3. The vertical line shows the Fermi energy.
Fig. 9
Fig. 9
Fermi surfaces of W2N3 for the band number (a) 41, (b) 42, (c) 43, and (d) 44.
Fig. 10
Fig. 10
(a) Real part of dielectric function, (b) imaginary part of dielectric function, (c) real part of refractive index, (d) extinction coefficient, (e) absorption coefficient, (f) optical conductivity, (g) reflectivity, and (h) loss function of W2N3 as a function of photon energy for two different polarizations of the electric field.
Fig. 11
Fig. 11
Temperature and pressure dependent bulk modulus of W2N3.
Fig. 12
Fig. 12
Temperature and pressure dependent variations of volume thermal expansion coefficient of W2N3.
Fig. 13
Fig. 13
Temperature and pressure dependent variations of internal energy of W2N3.
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