Seeing the Unseen: The Structural Influence of the Lone Pair Electrons in PbWO4

Bryce G Mullens; Frederick P Marlton; Maria K Nicholas; Ahmadi Jaya Permana; Maxim Avdeev; Supratik Mukherjee; Ganapathy Vaitheeswaran; Cheng Li; Jue Liu; Philip A Chater; Brendan J Kennedy

doi:10.1021/acs.inorgchem.4c00866

Seeing the Unseen: The Structural Influence of the Lone Pair Electrons in PbWO₄

Inorg Chem. 2024 Jun 17;63(24):11176-11186. doi: 10.1021/acs.inorgchem.4c00866. Epub 2024 May 20.

Authors

Bryce G Mullens¹, Frederick P Marlton^{1

2}, Maria K Nicholas¹, Ahmadi Jaya Permana^{1

3}, Maxim Avdeev^{1

4}, Supratik Mukherjee⁵, Ganapathy Vaitheeswaran⁶, Cheng Li⁷, Jue Liu⁷, Philip A Chater⁸, Brendan J Kennedy¹

Affiliations

¹ School of Chemistry, The University of Sydney, Sydney, New South Wales 2006, Australia.
² Centre for Clean Energy Technology, School of Mathematical and Physical Sciences, Faculty of Science, University of Technology Sydney, Sydney, New South Wales 2007, Australia.
³ Department of Chemistry, Faculty of Science and Technology, Universitas Airlangga, Surabaya 60115, Indonesia.
⁴ Australian Centre for Neutron Scattering, ANSTO, New Illawarra Road, Lucas Heights, New South Wales 2234, Australia.
⁵ Advanced Center of Research in High Energy Materials (ACRHEM), University of Hyderabad, Prof. C. R. Rao Road, Gachibowli, Hyderabad, Telangana 500046, India.
⁶ School of Physics, University of Hyderabad, Prof. C. R. Rao Road, Gachibowli, Hyderabad, Telangana 500046, India.
⁷ Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
⁸ Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire OX11 0DE, U.K.

PMID: 38767205
DOI: 10.1021/acs.inorgchem.4c00866

Abstract

Pair distribution function (PDF) analysis of the scheelite-type material PbWO₄ reveals previously unidentified short-range structural distortions in the PbO₈ polyhedra and WO₄ tetrahedra not observed in the similarly structured CaWO₄. These local distortions are a result of the structural influence of the Pb²⁺ 6s² lone pair electrons. These are not evident from the Rietveld analysis of synchrotron X-ray or neutron powder diffraction data, nor do they strongly influence the X-ray PDF (XPDF). This illustrates the importance of neutron PDF (NPDF) in the study of such materials. First-principles density function theory (DFT) calculations show that the Pb²⁺ 6s² electrons are hybridized with the O^2- 2p electrons near the Fermi level. The presence of local-scale distortions has previously been neglected in studies of structure-functionality relationships in PbWO₄ and other scheelite-structured photocatalytic materials, including BiVO₄, and this observation opens new avenues for their optimization.