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The structural and electronic properties of the rutile-type oxide beta-PbO2 (plattnerite) are studied by neutron and synchrotron radiation powder diffraction and first-principles density functional theory (DFT) calculations~[1]. The motivation to study the electronic properties of beta-PbO2 gained some additional impact related to the possible existence of topologically nontrivial [2,3] semimetallic states. Both diffraction measurements and DFT calculations show that beta-PbO2 has a CaCl2-type orthorhombic structure (space group Pnnm) instead of the widely accepted beta-PbO2 rutile-type tetragonal structure (space group P42/mnm).
This symmetry lowering in beta-PbO2 is a robust effect observed at ambient pressure at temperatures between 100 and 400 K. The orthorhombic symmetry rules out the possibility of a semimetallic symmetry-protected state in beta-PbO2. Both diffraction measurements and DFT calculations show an anisotropy of thermal expansion, atomic vibrations and elastic constants of β-PbO2 along the [100] and [010] directions.
[1] P. Fabrykiewicz, R. Przeniosło, N. Gonzalez Szwacki, I. Sosnowska, E. Suard and F. Fauth, Phys. Rev. B103, 064109 (2021).
[2] M. Z. Hasan and C. L. Kane, Rev. Mod. Phys. 82, 3045 (2010).
[3] B. Peng, I. Bravic, J. L. MacManus-Driscoll, and B. Monserrat, Phys. Rev. B 100, 161101(R) (2019).
