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~. 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  and  directions.
 P. Fabrykiewicz, R. Przeniosło, N. Gonzalez Szwacki, I. Sosnowska, E. Suard and F. Fauth, Phys. Rev. B103, 064109 (2021).
 M. Z. Hasan and C. L. Kane, Rev. Mod. Phys. 82, 3045 (2010).
 B. Peng, I. Bravic, J. L. MacManus-Driscoll, and B. Monserrat, Phys. Rev. B 100, 161101(R) (2019).