Data di Pubblicazione:
2004
Citazione:
On the role of data quality in experimental charge density studies / R. Destro, L. Loconte, L. Lo Presti, P. Roversi, R. Soave. - In: ACTA CRYSTALLOGRAPHICA. SECTION A, FOUNDATIONS OF CRYSTALLOGRAPHY. - ISSN 0108-7673. - 60:5(2004), pp. 365-370. [10.1107/S0108767304014813]
Abstract:
High-resolution X-ray diffraction data were collected at T = 19 K from two similar spherical crystals of the fungal metabolite citrinin, C13H14O5. The two data sets were of markedly different quality, one data set (MQ, medium quality) comprising a single octant of the reciprocal lattice and including reflections with obviously peculiar intensity profiles while the second (HQ, high quality) comprised a hemisphere of reflections and showed no flawed profiles. Parallel multipolar refinements were carried out for both. While most of the resulting geometric parameters, including bond lengths and angles, were in close agreement (the standard uncertainties were approximately twice as large for
the MQ data, reflecting the smaller number of observations), the agreement is noticeably worse for electronic properties such as electron densities and their
Laplacians at the bond and ring critical points. These latter features are especially sensitive to the quality of the low-angle (and strong) intensities, which
was not high for the MQ data. By contrast, the magnitudes of the molecular
dipole moment from the two experiments are the same within 1 standard uncertainty, with an angle of about 13 deg between the two vectors. It is concluded that only true high-quality data allow a fully significant and quantitative analysis of the details of the experimental electron density rho(exp), while high-resolution medium-quality data, measured at very low temperature and adequately processed, can still be used for a qualitative analysis, or for the derivation of overall electronic properties.
Tipologia IRIS:
01 - Articolo su periodico
Keywords:
single-crystal X-ray diffraction ; electron density ; topological analysis ; molecular electric moments ; data quality
Elenco autori:
R. Destro, L. Loconte, L. Lo Presti, P. Roversi, R. Soave
Link alla scheda completa: