An ab-initio study of the rôle of lone pairs in the structure and insulator–metal transition in SnO and PbO (original) (raw)
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Ferroelectrics, 1992
ABSTRACT The incommensurate phase of the lead monoxide PbO (224 K)is characterized by Raman scattering and X-ray diffraction. We show that the isomorphic compound SnO doesn't displaylong range incommensurate behaviour; however one observes diffuse scattering at 295 K and an anomaly on the a cell parameter temperature dependence below 100 K. The two different behaviours have been correlated with the stereochemical influence of the electron lone pairs of the divalent Pb and Sn atoms.
AIP Advances
In this work, using the Quantum ESPRESSO package, density functional theory was used to study the effects of different metal dopants on the structural and electronic properties of tetragonal α-PbO. Tetragonal α-PbO has attracted attention due to its application in various optoelectronic devices. However, in order to apply it in these technologies suitably, its properties have to be improved since it has low electronic conductivity. In this study, nine different metals from alkali metals, p-block metals, and 3d-transition metals have been used as dopants to investigate its electronic properties. Moreover, the performance of four pseudopotentials was tested. Via the partial density of state and band structure calculations, an indirect bandgap was found for pristine α-PbO. The generalized gradient approximation of the Perdew–Burke–Ernzerhof exchange correlation with ultrasoft pseudopotential gives 1.75 eV for pristine α-PbO, which decreased during the incorporation of different metal d...
Electronic properties of the Sn1−xPbxO alloy and band alignment of the SnO/PbO system: a DFT study
Scientific Reports
Tin monoxide (SnO) has attracted attention due to its p-type character and capability of ambipolar conductivity when properly doped, properties that are beneficial for the realization of complementary oxide thin film transistors technology, transparent flexible circuits and optoelectronic applications in general. However, its small fundamental band gap (0.7 eV) limits its applications as a solar energy material, therefore tuning its electronic properties is necessary for optimal performance. In this work, we use density functional theory (DFT) calculations to examine the electronic properties of the Sn1−xPbxO ternary oxide system. Alloying with Pb by element substitution increases the band gap of SnO without inducing defect states in the band gap retaining the anti-bonding character of the valence band maximum which is beneficial for p-type conductivity. We also examine the properties of the SnO/PbO heterojunction system in terms of band alignment and the effect of the most common i...
This work employs DFT to investigate the effect of metal doping (Li, Sn, Ni, Cu, and Co) on the optical, electrical, and structural characteristics of α-PbO. Li-doped α-PbO is the only doped material whose volume was increased in the structural investigation. Thus, for pristine, Li-doped, Sn-doped, Nidoped, Cu-doped, and Co-doped α-PbO, the obtained a lattice parameters were 4.066, 4.192, 3.955, 3.922, 3.820, and 3.799 nm, respectively, and the c lattice parameters were 5.26, 5.622, 4.953, 3.907, 3.672, and 3.551 nm, respectively. The indirect bandgap values of pristine, Li-doped, Sn-doped, Ni-doped, Cu-doped, and Co-doped α-PbO were found to be 1.78, 1.59, 1.56, 1.25, 1.33, and 1.13 eV, respectively. The partial density of states (PDOS) shows the contribution of Pb 6s for deep valence states, O 2p for shallow valence states, and Pb 6p orbitals for conduction band states. Comprehensive analyses were conducted on the impacts of doped metals on optical properties, including dielectric functions, electron energy loss, optical conductivity, refractive index, extinction coefficient, and reflectivity. This study offers useful guidelines for doing experiments with metal oxides in various fields, including energy storage and photocatalysis.
Electronic and structural properties of SnO under pressure
Physical Review B, 2005
Pressure-induced changes in the electronic and structural properties of tin monoxide are examined by means of ab initio density-functional calculations. Also, the pressure shifts of the A 1g and E g zone-center phonon modes are derived. The results are compared to recent experimental high-pressure data as well as to previous calculations for ambient conditions. In agreement with earlier findings we observe that the Sn-5s lone pair is not inert but hybridizes with the O-p states. Differences in that respect between SnO and PbO are shown to be a "relativistic dehybridization effect" caused by the large mass-velocity downshift of the Pb-6s states. SnO is a small-gap ͑indirect͒ semiconductor at ambient pressure, but an insulator-metal transition occurs as pressure is applied. The transition is estimated to occur around 5 GPa. The gap depends sensitively on the distance between the layers dE gap / d ln͑c / a͒Ϸ21 eV.
PHYSICAL REVIEW LETTERS, 2006
Structural distortions in post-transition metal oxides are often explained in terms of the influence of sp hybrid ''lone pairs.'' Evidence is presented here showing that this model must be revised. The electronic structures of prototypically distorted -PbO and -Bi 2 O 3 have been measured by high-resolution x-ray photoemission and soft x-ray emission spectroscopies. In contrast with the expectations of the lone pair model, a high density of metal 6s states is observed at the bottom of the valence band. The measurements are consistent with the results of density functional theory calculations.
2007
Theoretical investigations concerning the high-pressure polymorphs, the equations of state, and the phase transitions of SnO 2 have been performed using density functional theory at the B3LYP level. Total energy calculations and geometry optimizations have been carried out for all phases involved, and the following sequence of structural transitions from the rutile-type (P4 2 /mnm) driven by pressure has been obtained (the transition pressure is in parentheses): f CaCl 2 -type, Pnnm (12 GPa) f R-PbO 2 -type, Pbcn (17 GPa) f pyrite-type, Pa3 h (17 GPa) f ZrO 2 -type orthorhombic phase I, Pbca (18 GPa) f fluorite-type, Fm3 hm (24 GPa) f cotunnite-type orthorhombic phase II, Pnam (33 GPa). The highest bulk modulus values, calculated by fitting pressure-volume data to the second-order Birch-Murnaghan equation of state, correspond to the cubic pyrite and the fluorite-type phases with values of 293 and 322 GPa, respectively.