New Directions in Pseudoatom-Based X-Ray Charge Density Analysis

2010 ◽  
pp. 1-25 ◽  
Author(s):  
Tibor Koritsanszky ◽  
Anatoliy Volkov ◽  
Michal Chodkiewicz
Keyword(s):  
Charge Density ◽  
X Ray ◽  
New Directions ◽  
Density Analysis

Chemical Applications of X-ray Charge-Density Analysis

2001 ◽  
Vol 101 (6) ◽  
pp. 1583-1628 ◽  
Author(s):  
Tibor S. Koritsanszky ◽  
Philip Coppens
Keyword(s):  
Charge Density ◽  
X Ray ◽  
Density Analysis

Comparative study of X-ray charge-density data on CoSb3

2013 ◽  
Vol 69 (6) ◽  
pp. 570-582 ◽  
Author(s):  
Mette Stokkebro Schmøkel ◽  
Lasse Bjerg ◽  
Finn Krebs Larsen ◽  
Jacob Overgaard ◽  
Simone Cenedese ◽  
...  
Keyword(s):  
Charge Density ◽  
High Performance ◽  
Theoretical Data ◽  
High Energy ◽  
Data Sets ◽  
High Symmetry ◽  
X Ray ◽  
Structure Factors ◽  
Small Crystals ◽  
Density Analysis

CoSb3is an example of a highly challenging case for experimental charge-density analysis due to the heavy elements (suitability factor of ∼0.01), the perfect crystallinity and the high symmetry of the compound. It is part of a family of host–guest structures that are potential candidates for use as high-performance thermoelectric materials. Obtaining and analysing accurate charge densities of the undoped host structure potentially can improve the understanding of the thermoelectric properties of this family of materials. In a previous study, analysis of the electron density gave a picture of covalent Co–Sb and Sb–Sb interactions together with relatively low atomic charges based on state-of-the-art experimental and theoretical data. In the current study, several experimental X-ray diffraction data sets collected on the empty CoSb3framework are compared in order to probe the experimental requirements for obtaining data of high enough quality for charge-density analysis even in the case of very unsuitable crystals. Furthermore, the quality of the experimental structure factors is tested by comparison with theoretical structure factors obtained from periodic DFT calculations. The results clearly show that, in the current study, the data collected on high-intensity, high-energy synchrotron sources and very small crystals are superior to data collected at conventional sources, and in fact necessary for a meaningful charge-density study, primarily due to greatly diminished effects of extinction and absorption which are difficult to correct for with sufficient accuracy.

scholarly journals Anisotropic displacement parameters for H atoms using an ONIOM approach

2006 ◽  
Vol 62 (5) ◽  
pp. 875-888 ◽  
Author(s):  
Andrew E. Whitten ◽  
Mark A. Spackman
Keyword(s):  
Neutron Diffraction ◽  
Charge Density ◽  
Ab Initio ◽  
Diffraction Data ◽  
Heavy Atom ◽  
Molecular Crystals ◽  
X Ray ◽  
Density Analysis ◽  
Anisotropic Displacement Parameters ◽  
Oniom Approach

X-ray diffraction data cannot provide anisotropic displacement parameters (ADPs) for H atoms, a major outstanding problem in charge-density analysis of molecular crystals. Although neutron diffraction experiments are the preferred source of this information, for a variety of reasons they are possible only for a minority of materials of interest. To date, approximate procedures combine rigid-body analysis of the molecular heavy-atom skeleton, based on ADPs derived from the X-ray data, with estimates of internal motion provided by spectroscopic data, analyses of neutron diffraction data on related compounds, or ab initio calculations on isolated molecules. Building on these efforts, an improved methodology is presented, incorporating information on internal vibrational motion from ab initio cluster calculations using the ONIOM approach implemented in GAUSSIAN03. The method is tested by comparing model H-atom ADPs with reference values, largely from neutron diffraction experiments, for a variety of molecular crystals: benzene, 1-methyluracil, α-glycine, xylitol and 2-methyl-4-nitroaniline. The results are impressive and, as the method is based on widely available software, and is in principle widely applicable, it offers considerable promise in future charge-density studies of molecular crystals.

scholarly journals X-ray charge-density analysis of vanadium diboride: a comparison of experiment and theory

2010 ◽  
Vol 66 (a1) ◽  
pp. s94-s94
Author(s):  
Bürgehan Terlan ◽  
Horst Borrmann ◽  
Alexey Baranov ◽  
Carina Börrnert ◽  
Frank R. Wagner ◽  
...  
Keyword(s):  
Charge Density ◽  
X Ray ◽  
Density Analysis ◽  
Vanadium Diboride

Charge-density analysis in polymorphs of urea–barbituric acid co-crystals

2011 ◽  
Vol 67 (2) ◽  
pp. 144-154 ◽  
Author(s):  
Marlena Gryl ◽  
Anna Krawczuk-Pantula ◽  
Katarzyna Stadnicka
Keyword(s):  
Hydrogen Bond ◽  
High Resolution ◽  
Hydrogen Bonds ◽  
Charge Density ◽  
Barbituric Acid ◽  
Van Der Waals Interactions ◽  
X Ray Diffraction ◽  
X Ray ◽  
Density Analysis ◽  
Resolution Single

High-resolution single-crystal X-ray diffraction measurements at 100 K were performed for the two polymorphs of urea–barbituric acid co-crystals: (I) P21/c and (II) Cc. Experimental and theoretical charge density and its properties were analysed for (I) and (II) in order to confirm the previous observation that in the polymorphs studied the barbituric acid molecules adopt different mesomeric forms, leading to different hydrogen-bond systems. Koch and Popelier criteria were applied to distinguish between hydrogen bonds and van der Waals interactions in the structures presented.

Sign in / Sign up

Export Citation Format

Share Document