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Refinement of the structure of orthorhombic PbO (massicot) by Rietveld analysis of neutron powder diffraction data
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1985
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Crystal StructureEngineeringChemistryStructure DeterminationStructure ElucidationMetallic PbInterlayer GapSurface ReconstructionMaterials SciencePhysicsRietveld AnalysisQuantum ChemistryCrystallographyCrystal Structure DesignNatural SciencesApplied PhysicsOrthorhombic PboNeutron ScatteringPb Atoms
M r = 223.19, orthorhombic, Pbcm , a = 5.8931 (1), b = 5. 4904 (1), c = 4.7528 (1) A, V = 153.78 (1) A 3 , Z = 4, D x = 9.640 g cm -3 , lambda = 1.893 A, mu = 0. 210 cm -1 , F(000) = 608 fm 2 , T = 295 K, R wp = 0.0846 for 2623 step intensities, R B = 0.0182 for 98 reflections. The structure consists of sheets 2.71 A thick, separated by 3.19 A in the (100) direction, and corrugated parallel to (001). The Pb atoms are located on the surface of these layers, differing little from their positions in metallic Pb, but square-pyramidally bonded to four O atoms in the interior of the layers. The O atoms are in distorted tetrahedral coordination by Pb. The sheets are bonded together solely by van der Waals interactions between lone-pair orbitals on Pb atoms separated by 3.977 (2) and 4. 206 (1) A across the interlayer gap. The puckered geometry of the sheets is stabilized by similar lone-pair interactions between Pb atoms separated by 3.728 (2) A across the corrugations.