High-Pressure Phases of SnO and PbO: A Density Functional Theory Combined with an Evolutionary Algorithm Approach
Tin monoxide, SnO, and its analog, lead monoxide, PbO, have the same tetragonal <i>P4/nmm</i> structure, shaped by nonbonding dispersion forces and lone pairs. The high-pressure phases of SnO and PbO have been explored in several experimental and theoretical studies, with conflicting res...
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| Autores principales: | , |
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| Formato: | article |
| Lenguaje: | EN |
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MDPI AG
2021
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| Materias: | |
| Acceso en línea: | https://doaj.org/article/8dc20e087f4c4db385d3490ca9918739 |
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| Sumario: | Tin monoxide, SnO, and its analog, lead monoxide, PbO, have the same tetragonal <i>P4/nmm</i> structure, shaped by nonbonding dispersion forces and lone pairs. The high-pressure phases of SnO and PbO have been explored in several experimental and theoretical studies, with conflicting results. In this study, the high-pressure structures of SnO and PbO are investigated using density functional theory calculations combined with an evolutionary algorithm to identify novel high-pressure phases. We propose that the monoclinic <i>P2<sub>1</sub>/m</i> SnO and orthorhombic <i>Pmmn</i> PbO phases, which are metastable at 0 GPa, are a slight rearrangement of the tetragonal <i>P4/nmm</i>-layered structure. These orthorhombic (and their closely related monoclinic) phases become more favored than the tetragonal phase upon compression. In particular, the transition pressures to the orthorhombic γ-phase <i>Pmn2<sub>1</sub></i> of SnO/PbO and the monoclinic phase <i>P2<sub>1</sub>/m</i> of SnO are found to be consistent with experimental studies. Two new high-pressure SnO/PbO polymorphs are predicted: the orthorhombic <i>Pbcm</i> phase of SnO and the monoclinic <i>C<sub>2</sub>/m</i> of PbO. These phases are stabilized in our calculations when P > 65 GPa and P > 50 GPa, respectively. The weakening of the lone pair localization and elastic instability are the main drivers of pressure-induced phase transitions. Modulations of the SnO/PbO electronic structure due to structural transitions upon compression are also discussed. |
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