Carrier effective masses and thermoelectric properties of novel Ag₃AuSe₂ and Ag₃AuTe₂ compounds

Abstract

The carrier effective masses as well as thermoelectric and electronic properties of ternary chalcogenides compounds of the form Ag3AuX2(X = Se, Te) have been studied using first-principles method based on density functional theory. For the treatment of exchange-correlation energy, we have used the generalized gradient approximation (GGA) by Perdew, Burke and Ernzerhof (PBE-GGA) and Wu–Cohen (WU-GGA) schemes. Both the compounds (Ag3AuSe2 and Ag3AuTe2) are direct bandgap semiconductors. The p-type nature of these compounds is confirmed by the effective mass calculations. In thermoelectric measurements, different parameters (electrical conductivity, carrier concentration, Seebeck coefficient, thermal conductivity and thermoelectric power) are calculated. It is found that all these parameters increase with the increase in temperature for both the compounds. The obtained results for these compounds such as the direct bandgap nature and their high value of the thermoelectric power make them valuable candidates for different device applications.

Transport and optical properties of the chiral semiconductor Ag3AuSe2

“…Figure 5(a) shows the experimental optical conductivity σ 1 and σ 2 of Ag 3 AuSe 2 measured at room temperature. No sign of a free‐carrier response (intraband transition) was captured in σ 1 down to the lowest frequency measured, consistent with the measured high resistivity and finite gap predicted from previous calculations [10–12] . The band gap edge of Ag 3 AuSe 2 was extracted from the squared optical absorption coefficient α 2 as shown in Figure 5(b).…”

“…No sign of a freecarrier response (intraband transition) was captured in σ 1 down to the lowest frequency measured, consistent with the measured high resistivity and finite gap predicted from previous calculations. [10][11][12] The band gap edge of Ag 3 AuSe 2 was extracted from the squared optical absorption coefficient α 2 as shown in Figure 5(b). From Fermi's golden rule and the joint density of states for parabolic bands, the frequency dependence of absorption near a direct band gap (E G ) is represented as: [31] a ¼ ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi ffi w À E g p for ω > E G .…”

“…Faizan used density functional theory (DFT) to evaluate the promise of Ag 3 AuSe 2 for thermoelectric applications and found the band gap to be about 1.0 eV using the generalized gradient approximation (GGA). [10,11] However, published resistivity measurements (with the aforementioned question of sample purity) [6] gave lower activation energy of around 0.5 eV. Calculations using the local density approximation (LDA), by Fang, et al are expected to underestimate the band gap and found a gap of about 0.2 eV.…”

“…More recently, the chirality and possible narrow band gap (or possibility of band inversion and topological phenomena) have led to a renewed computational focus on Ag 3 AuSe 2 . Faizan used density functional theory (DFT) to evaluate the promise of Ag 3 AuSe 2 for thermoelectric applications and found the band gap to be about 1.0 eV using the generalized gradient approximation (GGA) [10,11] . However, published resistivity measurements (with the aforementioned question of sample purity) [6] gave lower activation energy of around 0.5 eV.…”