Pressure-Induced Enhanced Optical Absorption in Sulvanite Compound Cu₃TaX₄ (X = S, Se, and Te): An ab Initio Study

Abstract

Ab initio study on the family of ternary copper chalcogenides Cu 3 TaX 4 (X = S, Se, and Te) is performed to investigate the suitability of these compounds to applications as photovoltaic absorber materials. The density functional theory based full potential linearized augmented plane wave method (FP-LAPW method) is employed for computational purposes. The electronic structure and optical properties are determined including electron–electron interaction and spin–orbit coupling (SOC), within the generalized gradient approximation plus Hubbard U (GGA+ U ) and GGA+ U +SOC approximation. The large optical band gaps of Cu 3 TaS 4 and Cu 3 TaSe 4 considered ineffective for absorber materials, and also the hole effective mass has been modulated through applied pressure. These materials show extreme resistance to external pressure, and are found to be stable up to a pressure range of 10 GPa, investigated using phonon dispersion calculations. The observed optical properties and the absorption coefficients within the visible-light spectrum make these compounds promising materials for photovoltaic applications. The calculated energy and optical band gaps are consistent with the available literature and are compared with the experimental results where available.

A Thorough Investigation of Electronic, Optical, Mechanical, and Thermodynamic Properties of Stable Glasslike Sodium Germanate under Compressive Hydrostatic Pressure: Ab Initio Study

“…Thus, at 20 and 25 GPa, the optical parameters that have been presented in terms of photon energy (eV) were enhanced as compared to P = 0–15 GPa. Similarly, pressure-dependent enhancement of optical properties was formerly reported for halide perovskite, sulvanite compounds, and glass materials. − However, compared to these compounds, Na 2 GeO 3 has shown better enhancement due to the resultant direct band electronic transition at P ∼ 20 GPa.…”

Engineering of Hydrogenated (6,0) Single-Walled Carbon Nanotube under Applied Uniaxial Stress: A DFT-1/2 and Molecular Dynamics Study

“…Here we are mostly focused on the absorption coefficient (α a ) and refractive index ( n ) calculated from the dielectric function ϵ(ω) = ϵ 1 (ω) + i ϵ 2 (ω). The real part ϵ 1 (ω) characterizes the degree of polarization under an external electric field, and the imaginary part ϵ 2 (ω) characterizes the interband electronic transition from occupied states to unoccupied states. , ϵ 2 (ω) can be directly calculated from the one-electron orbitals and energies obtained from the Kohn–Sham equations. It is given by the equation below , ε 2 false( ω false) = ℏ 2 e 2 π m 2 ω 2 ∑ n n ′ ∫ k d 3 k false| < k ⇀ n false| p⃗ | k ⇀ n ′ > | 2 false[ 1 − f ( k ⇀ n ) false] δ false( E k ⇀ n − E k ⇀ n false′ − normalℏ ω false)…”

“…The real part ϵ 1 (ω) characterizes the degree of polarization under an external electric field, and the imaginary part ϵ 2 (ω) characterizes the interband electronic transition from occupied states to unoccupied states. 87 , 88 ϵ 2 (ω) can be directly calculated from the one-electron orbitals and energies obtained from the Kohn–Sham equations. It is given by the equation below 89 , 90 where is the momentum operator, is the eigenfunction of the eigenvalue, and is the Fermi Distribution function.…”