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Exploring charge density analysis in crystals at high pressure: data collection, data analysis and advanced modelling

DOI: 10.1107/S2052520617008356 DOI Help

Authors: Nicola Casati (Swiss Light Source) , Alessandro Genoni (CNRS; Université de Lorraine) , Benjamin Meyer (CNRS; Université de Lorraine) , Anna Krawczuk (Jagiellonian University) , Piero Macchi (University of Bern)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acta Crystallographica Section B Structural Science, Crystal Engineering And Materials , VOL 73 , PAGES 584 - 597

State: Published (Approved)
Published: August 2017
Diamond Proposal Number(s): 7741

Abstract: The possibility to determine electron-density distribution in crystals has been an enormous breakthrough, stimulated by a favourable combination of equipment for X-ray and neutron diffraction at low temperature, by the development of simplified, though accurate, electron-density models refined from the experimental data and by the progress in charge density analysis often in combination with theoretical work. Many years after the first successful charge density determination and analysis, scientists face new challenges, for example: (i) determination of the finer details of the electron-density distribution in the atomic cores, (ii) simultaneous refinement of electron charge and spin density or (iii) measuring crystals under perturbation. In this context, the possibility of obtaining experimental charge density at high pressure has recently been demonstrated [Casati et al. (2016)[Casati, N., Kleppe, A., Jephcoat, A. & Macchi, P. (2016). Nat. Commun. 7, 10901.]. Nat. Commun. 7, 10901]. This paper reports on the necessities and pitfalls of this new challenge, focusing on the species syn-1,6:8,13-biscarbonyl­[14]annulene. The experimental requirements, the expected data quality and data corrections are discussed in detail, including warnings about possible shortcomings. At the same time, new modelling techniques are proposed, which could enable specific information to be extracted, from the limited and less accurate observations, like the degree of localization of double bonds, which is fundamental to the scientific case under examination.

Journal Keywords: X-ray-constrained wavefunctions; multipolar model; high pressure diffraction; charge density

Subject Areas: Physics, Technique Development

Instruments: I15-Extreme Conditions