The structural, stability, electronic, optical and thermodynamic properties of MoX2 (X= S, Se, and Te) under hydrostatic pressures: a plasmon approach and first-principle study

Abstract

Context: The new equations have been developed for the structural and electronic properties using the plasmon calculations for the first time for 2-D MoX₂ structures. Literature shows still an extensive study is required on the stability and optical properties of MoX2 under different hydrostatic pressures and thermal properties under different temperatures using the first principles, for electronic industrial applications. The stability is analyzed using binding energy and phonon calculations. The phase transition of metallization of MoX₂ is discussed using band structure calculations under different hydrostatic pressures. The calculated work function shows the photoemission starts from the threshold frequency of 4.189×10⁴ cm^-1, 3.184×10⁴ cm^-1, and 3.651×10⁴ cm^-1, respectively, for MoS₂, MoSe₂, and MoTe₂ materials. The optical properties such as refractive index n(0), and static dielectric permittivity ε(0) for three successive materials are calculated under different hydrostatic pressures, applicable for optoelectronic applications. The calculated theoretical and computational values agree well with each other and also agree with reported and experimental values. Some of the values are calculated for the first time.

Methods: The theoretical equations are derived using the molecular weight, effective valence electrons, and density of molecule of MoX₂ structures. The simulation work is performed using GGA-PBE approximation in the CASTEP simulation package with DFT+D semi-empirical dispersion correction. An ultra-soft pseudopotential representation calculates the electronic and optical properties with a finite basis set kinetic energy cut-off of 381.0 eV. Each geometry has been optimized using Broyden, Fletcher, Goldfarb, and Shanno's (BFGS) algorithm for 100 iterations with a fixed basis quality variable cell method and finite electronic minimization parameters. The phonon calculations were performed using TDFT with a kinetic energy cut of 460 eV in a norm-conserving linear response method. The interpolation with a finite dispersion quality and q-vector grid spacing is performed.

Keywords: Electronic properties; First-principles; Hydrostatic pressures; Optical properties; Transition metal dichalcogenides.