Electronic structure of crystalline binary and ternaryCd−Te−Ocompounds

Abstract

The electronic structure of crystalline CdTe, CdO, α-TeO2, CdTeO3 and Cd3TeO6 is studied by means of first principles calculations. The band structure, total and partial density of states, and charge densities are presented. For α-TeO2 and CdTeO3, Density Functional Theory within the Local Density Approximation (LDA) correctly describes the insulating character of these compounds. In the first four compounds, LDA underestimates the optical bandgap by roughly 1 eV. Based on this trend, we predict an optical bandgap of 1.7 eV for Cd3TeO6. This material shows an isolated conduction band with a low effective mass, thus explaining its semiconducting character observed recently. In all these oxides, the top valence bands are formed mainly from the O 2p electrons. On the other hand, the binding energy of the Cd 4d band, relative to the valence band maximum, in the ternary compounds is smaller than in CdTe and CdO.

First principles electronic structure and band gap pressure coefficient for cadmium‐oxide

“…[12] LDA-SR −0.6 Ref. [14] LDA characterized with the pressure coefficient of the gap; i.e., the derivative of the gap with respect to pressure. It has been noted [35] that, in many cases, the fundamental band gap is a nearly linear function of the lattice constant, in which case, the theoretical pressure coefficient can be determined with good precision by first performing a linear fit to E g versus a and then applying the relationship…”

“…Additional HF calculations with correlation corrections were conducted in 1991 [10]. More recent calculations for CdO have generally relied upon density functional theory (DFT) [11] based models, including the local density approximation (LDA) [12][13][14], the generalized gradient approximation (GGA) [15], and the screened exchange LDA (sX-LDA) [16]. Given the amount of work that has been carried out to date, it is somewhat surprising that the various DFT calculations of the band gaps for CdO are in rather poor quantitative agreement.…”

Structural and magnetic dimers in the spin-gapped systemCuTe2O5

“…The exponents ζ and ζ ′ of the Slater type atomic orbitals Te 5s/5p listed in Table I are greater than those of the atomic orbital calculations 29 by the factor of 1.45, because such values are needed in reproducing the band gap of α-TeO 2 by EHTB calculations. 30 The results of our examination of the spin dimers (i.e.the structural units containing two spin sites) in CuTe 2 O 5 are listed in Table II. We identified the strongest interaction J 6 to be of antiferromagnetic SSE type mediated by O-Te-O bridges and the second strongest J 1 to be the antiferromagnetic SE interaction within the structural dimer Cu 2 O 8 , yielding a ratio (∆e 1 ) 2 /(∆e 6 ) 2 = J 1 /J 6 = 0.59.…”

Photoluminescence properties of the ZnO–CdO–TeO2 system doped with the Tb3+and Yb3+ ions

“…a is the absorption coefficient, which is proportional to PAS, i.e., apPAS. We have assumed direct transitions as ZnO, CdO, TeO 2 , and CdTeO 3 present direct transitions [13][14][15]. The inset in Fig.…”