Electronic structure of ternary thallium chalcogenide compounds

Abstract

The electronic structures of the ternary thallium chalcogenide compounds, TlGaSe 2 and TlGaS 2 are studied, using the linear muffin-tin orbital (LMTO) method. The calculated band dispersion shows that both compounds are indirect gap semiconductors. For both compounds, the top of the valence bands is located at Γ. For TlGaSe 2 , the bottom of the conduction band is located along the Z(0, 0, -5)-L(0.5, 0.5, -0.5) line. For TlGaS 2 , the bottom of the conduction band is located along the Γ -Y(0, 1, 0) line. An inspection of the LMTO wave functions shows that the valence band top has the character of Tl : 6s -Se : 4p or S : 3p antibonding state, while the conduction band bottom has the character of Tl : 6p -Se : 4p or S : 3p antibonding state.

Vacancy Formation Energy for the Charged and Neutral States of TlGaSe$_{2}$ Crystal

“…This, in their turn, indicates that TlGaSe 2 is an indirect gap semiconductor with the indirect gap from  to -Y line of 0.87 eV, while the direct gap at the -point is 0.99 eV. Indirect scenario of bands at the energy gap is favoured by other works, e.g., [18][19][20][21] too. However, the particular indirect schemes vary from work to work according to the earlier works [18,19]: the additional valence band maximum on Y line might be responsible for the indirect scenario.…”

“…However, the particular indirect schemes vary from work to work according to the earlier works [18,19]: the additional valence band maximum on Y line might be responsible for the indirect scenario. Nevertheless, the later works [20,21] and the present calculations, which used more advanced computation techniques, commonly advocate the conduction band bottom that is not in -point. At the same time, the just mentioned works specify different positions of this bottom in the BZ.…”

Compositional dependence of refractive index and oscillator parameters in TlGaS2xSe2(1−x) layered mixed crystals (0 ≤ x ≤ 1)

“…The theoretical studies on the electronic band structure of TlGaSe 2 crystals have been accomplished using the pseudopotential method [34], the screened-exchange local density approximation [35] and the linear muffin-tin orbital method [36]. Abdullaeva and Mamedov [34] and Johnsen et al [35] found that the valence band maximum is located at the G point of the Brillouin zone, while the conduction band minimum occurs along the GeY direction.…”

Electron-Deformational Phase Transitions in a TlGaSe2Layered Crystal

“…1) • [10]. The band structure of the TlGaSe 2 layered crystal has been calculated initially by means of the semi-empirical pseudopotential method [11,12], and next by ab initio methods [13], however in an inappropriate Brillouin zone. Our recent ab initio DFT-based calculations within a relevant BZ of the monoclinic base-centered lattice [14] have revealed that the band structure of TlGaSe 2 exhibits a complicated form in the vicinity of the energy gap, see Fig.…”