Bo Brummerstedt Iversen is professor of chemistry at Aarhus University (AU). He is VILLUM Investigator, Director of the AU Center for Integrated Materials Research (iMAT) and General Secretary and Treasurer of the IUCr. He obtained his PhD degree from AU in 1995, and following a post doc period at University of California in Santa Barbara he returned to AU in 1998 and eventually became Full Professor and Chair of Inorganic Chemistry in 2004. He is one of few Danish scientists holding both a Doctor of Science degree (AU, 2002) and a Doctor of Technology degree (DTU, 2010). He is PI on the DanMAX and SINCRYS beamline projects at MAX4. He is a Fellow of the Royal Danish Academy of Science and Letters, and awards include the Queen Margrethe II Science Prize, the Danish Elite Researcher Award, the Grundfos Prize and the AU Science Prize. He was Knighted by Queen Margrethe II in 2015. Prof. Iversen has been single responsible supervisor on 57 PhD degrees, 90 Master degrees and 87 bachelor degrees. He has published ~540 peer review papers.
Lecture 12: Bo Brummerstedt Iversen
Chemical bonding and local order
Bo Brummerstedt Iversen
Department of Chemistry and iNANO, Aarhus University, DK-8000 Aarhus C, Denmark
X-ray diffraction has for decades been a key analytical tool in chemistry and materials science. Bragg intensities provide information about the average crystal structure, and if measured accurately to high resolution they allow determination of the electron density distribution in the unit cell of the crystal [1]. X-ray electron densities have for 50 years been used to test theories of chemical bonding in a vast range of systems, and recent examples from our group will be discussed [2-4]. However, in materials science crystals are often defect and this gives rise to diffuse scattering, which for many years has been analysed reciprocal space. We have instead used direct space 3D-(delta)PDF analysis to study high-performance thermoelectric materials Cu2Se [5], PbTe and PbS [6, 7], 19-e half-heusler Nb1-xCoSb [8, 9] and InTe [10], where the true local structure and chemical bonding significantly affects the properties.
[1] P. Coppens, X-ray charge densities and chemical bonding, Oxford University Press, New York, 1997.
[2] S. Sarkar et al., Chemical Bonding Origin of Glass Formation in Metal-Organic Frameworks, Angew. Chem. Intl. Ed. 2022, e202202742
[3] T. B. E. Grønbech et al., Chemical bonding in FeSb2, Chem. Eur. J. 2020, 26, 8651-8662
[4] E. S. Vosegaard et al., Synchrotron X-ray Electron Density Analysis of Chemical Bonding in Graphitic Carbon Nitride Precursor Melamine, Chem. Eur. J. 2022, 10.1002/chem.202201295
[5] N. Roth et al., Solving the disordered structure of β-Cu2-xSe using the three-dimensional difference pair distribution function, Acta Crystallogr. Sect. A, 75, 465–473 (2019)
[6] K. A. U. Holm et al., Temperature Dependence of Dynamic Dipole Formation in PbTe, Phys. Rev. B 102, 024112 (2020)
[7] K. A. U. Holm et al., Anharmonicity and correlated dynamics of PbTe and PbS studied by single crystal X-ray scattering, Phys. Rev. B 103, 224302 (2021)
[8] N. Roth et al., A simple model for vacancy order and disorder in defective half-Heusler systems, IUCrJ 7, 673-680 (2020)
[9] N. Roth et al., Tuneable local order in thermoelectric crystals, IUCR-J. 8, 695-702 (2021)
[10] J. Zhang et al, Direct observation of one-dimensional disordered diffusion channel in a chain-like thermoelectric with ultralow thermal conductivity, Nat. Commun. 12, 6709 (2021)