Download citation
Download citation
link to html
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). 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.

Supporting information

pdf

Portable Document Format (PDF) file https://doi.org/10.1107/S2052520617008356/lc5086sup1.pdf
Supporting figures and tables

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S2052520617008356/lc5086sup2.cif
CIF for MulitpoleModel_7p7GPa data

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S2052520617008356/lc5086sup3.cif
CIF for HP_Models_1.8-9.5GPa data


Follow Acta Cryst. B
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds