Electronic structure, structural properties, and dielectric functions of IV-VI semiconductors: PbSe and PbTe

Abstract

The electronic structure and frequency dependent dielectric function () of rocksalt semiconductors PbSe and PbTe are investigated using the local density approximation ͑LDA͒ and the generalized gradient approximation as two different exchange and correlation approximations, within the full-potential linearized augmented plane-wave approach. Spin-orbit coupling has been incorporated in the study. The results are presented and compared with other recent calculations and experimental data. Structural properties are also obtained by means of calculations of total energy as a function of lattice parameters. The bulk structural parameters are sensitive to the choice of exchange and correlation approximation. The essential features of the band structure and density of states of PbSe and PbTe are reproduced by our calculations and agree quite well with available experimental results. The position of the minimum energy gap is correctly predicted, although the value of the gap is as usual, underestimated by the local density approximation with respect to the experimental data. This gap value is improved by the inclusion of the generalized gradient approximation. Also, we have calculated the real ͓ 1 ()͔ and imaginary ͓ 2 ()͔ parts of () for both compounds, in the framework of the LDA scheme for exchange and correlation. The inclusion of spin-orbit coupling leads to a richer structure in both 1 () and 2 (). The agreement with experimental results is satisfactory.

Optical Investigation of Quantum Confinement in PbSe Nanocrystals at Different Points in the Brillouin Zone

“…We propose that transitions h, q, and i in Figure 4 correspond to optical transitions at another point in the Brillouin zone of PbSe than the Lpoint. In the band structure of bulk PbSe, there is a second bandgap at the S-point in the Brillouin zone with an energy of 1.60 eV, in excellent agreement with our experimental value of 1.57 eV for the extrapolation of transition h. [11,18] We assign h to a direct transition between a hole at the Spoint and an electron at the S-point, probably having S-symmetry envelope functions. Transitions q and i are assigned to transitions between higher-energy envelope functions at the S-point.…”

Resonant bonding leads to low lattice thermal conductivity

“…In addition, these materials have very weak sp-hybridization and the s-bands are well below the p-bands. Several past works show that PbTe, Bi 2 Te 3 and Bi satisfy this condition 13,16,17 and our calculations using density functional theory also present weak sp-hybridization in these materials (see Supplementary Note 1; Supplementary Figs 1-7). One very important feature of resonant bonding is that the electron density distribution is highly delocalized.…”

“…For example, in PbTe, sp-hybridization is small and the s-band is lower than the p-band by 1.5 eV (ref. 13). Therefore, we can consider only p-electrons for valence states and each atom has three valence electrons on average.…”

Gas−Liquid−Solid Phase Transition Model for Two-Dimensional Nanocrystal Self-Assembly on Graphite

“…13 For comparison we calculate the van der Waals attraction between two bare 12 nm PbSe nanocrystal cores, separated by 4.5 nm of olecic acid as measured for close-packed arrays, from Lifshitz-Hamaker theory as described previously. 2,4,10 The PbSe/ air/PbSe Hamaker constant is determined using literature optical constants, 14 and the imaginary part of PbSe's dielectric constant is modeled as a δ function centered at 2.5 eV. The calculated …”