scholarly journals Systematic Experimental Charge Density: Linking Structural Modifications to Electron Density Distributions

2015 ◽  
Vol 44 (1) ◽  
pp. 2-9 ◽  
Author(s):  
Isabelle L. Kirby ◽  
Mateusz B. Pitak ◽  
Simon J. Coles ◽  
Philip A. Gale
Keyword(s):  
Charge Density ◽  
Electron Density ◽  
Structural Modifications ◽  
Density Distributions ◽  
Experimental Charge Density

Revisiting the charge density analysis of 2,5-dichloro-1,4-benzoquinone at 20 K

2017 ◽  
Vol 73 (4) ◽  
pp. 654-659 ◽  
Author(s):  
Zhijie Chua ◽  
Bartosz Zarychta ◽  
Christopher G. Gianopoulos ◽  
Vladimir V. Zhurov ◽  
A. Alan Pinkerton
Keyword(s):  
Charge Density ◽  
Electron Density ◽  
Topological Analysis ◽  
Diffraction Measurement ◽  
X Ray Diffraction ◽  
Total Electron Density ◽  
Total Electron ◽  
Structure Factors ◽  
Density Analysis ◽  
Experimental Charge Density

A high-resolution X-ray diffraction measurement of 2,5-dichloro-1,4-benzoquinone (DCBQ) at 20 K was carried out. The experimental charge density was modeled using the Hansen–Coppens multipolar expansion and the topology of the electron density was analyzed in terms of the quantum theory of atoms in molecules (QTAIM). Two different multipole models, predominantly differentiated by the treatment of the chlorine atom, were obtained. The experimental results have been compared to theoretical results in the form of a multipolar refinement against theoretical structure factors and through direct topological analysis of the electron density obtained from the optimized periodic wavefunction. The similarity of the properties of the total electron density in all cases demonstrates the robustness of the Hansen–Coppens formalism. All intra- and intermolecular interactions have been characterized.

Comparative electronic analysis between hydrogen transfers in the CH4/CH3+, CH4/CH3•, and CH4/CH3− systems: on the electronic nature of the hydrogen (H−, H•, and H+) being transferred

1996 ◽  
Vol 74 (6) ◽  
pp. 1253-1262 ◽  
Author(s):  
Jordi Mestres ◽  
Miquel Duran ◽  
Juan Bertrán
Keyword(s):  
Charge Density ◽  
Electron Density ◽  
Hydrogen Transfer ◽  
Correlation Energy ◽  
Topological Analysis ◽  
Electronic Nature ◽  
Density Distributions ◽  
Density Maps ◽  
Density Analysis ◽  
A Charge

A comparative electronic analysis of the generally termed hydrogen transfers between CH4 and the CH3+, CH3•, and CH3− fragments is presented. These systems are taken as simple models of hydride (H−), hydrogen (H•), and proton (H+) transfers between two carbon fragments (in these simple cases being modelized by two CH3+, CH3•, and CH3− fragments, respectively). The study is mainly focused on analysis of the electronic nature of the type of hydrogen being transferred in each system, and for this reason a topological analysis of charge density distributions was performed. Computation of Bader atomic charges and construction of the charge density, gradient vector field, and Appalachian of the charge density maps reveal the specific features of the electronic nature of the transferring H−, H•, and H+. Moreover, characterization of the bond critical points on the charge density surface permits clarification of the differences in atomic interactions between H−, H•, and H+ and the carbon belonging to each CH3+, CH3•, and CH3− fragment, respectively. A charge density redistribution analysis is also performed to quantify the reorganization of the electron density when going from the reactant complex to the transition state. Finally, effects of inclusion of the correlation energy at the MP2 and CISD levels are also discussed. Key words: electron density, hydrogen transfer, topological density analysis, molecular similarity, Bader density analysis.

scholarly journals Synchrotron charge density studies of chemical bonding in the polymorphs of FeS2

2014 ◽  
Vol 70 (a1) ◽  
pp. C1338-C1338
Author(s):  
Jacob Overgaard ◽  
Mette Schmøkel ◽  
Lasse Bjerg ◽  
Simone Cenedese ◽  
Mads Jørgensen ◽  
...  
Keyword(s):  
Charge Density ◽  
Chemical Bonding ◽  
Negative Energy ◽  
X Ray Diffraction ◽  
Crystal Field Theory ◽  
Covalent Bonds ◽  
Density Distributions ◽  
Synchrotron Studies ◽  
Experimental Charge Density ◽  
Periodic Calculations

The experimental charge density (CD) distributions in both polymorphs of the photovoltaic compound iron-disulphide (FeS2; cubic pyrite and orthorhombic marcasite) will be described.[1] The CDs are determined by multipole modelling using synchrotron X-ray diffraction data collected at 10 K on extremely small single crystals (<10 mu) thus minimizing the influence of systematic errors such as absorption, extinction and TDS, and exploiting experiences gained from our recent synchrotron studies of CoSb3.[2] The analysis of the charge density in both polymorphs of FeS2 provides an opportunity to see how the different geometries affect local atomic properties, such as 2-center chemical bonding, atomic charges and d-orbital populations. In particular, the data and the resulting multipole models enable us to link the atomic-centered view that emerges from the multipole analysis with the band structure approach. This is carried out by combination with results from periodic calculations on the compounds in the experimental geometries using WIEN2k, thereby providing unambiguous answers to a number of unsolved issues regarding the nature of the bonding in FeS2. The chemical bonding will be characterized by topological analyses showing that the Fe-S bonds are polar covalent bonds, with only minor charge accumulation but significantly negative energy densities at the bond critical points. Using the IAM as reference, density is found to accumulate in-between the atoms, supporting a partial covalent bonding description. The homopolar covalent S-S interaction is seemingly stronger in pyrite than in marcasite, determined not only from the shorter distance but also from all topological indicators. Integrated atomic (Bader) charges show significantly smaller values than those estimation based on crystal-field theory of Fe2+, S-1. In connection with this, the experimentally derived d-orbital populations on Fe are found to deviate from the commonly assumed full t2g set, empty eg set, and they fit very well with the theoretical individual atomic orbitals projected density of states showing a higher dxy participation in the valence band in marcasite compared with pyrite. Thus, the differences between the two polymorphic compounds are directly reflected in their valence density distributions and d-orbital populations.

scholarly journals Experimental charge density of grossular under pressure – a feasibility study

IUCrJ ◽  
2020 ◽  
Vol 7 (3) ◽  
pp. 383-392 ◽  
Author(s):  
Roman Gajda ◽  
Marcin Stachowicz ◽  
Anna Makal ◽  
Szymon Sutuła ◽  
Jan Parafiniuk ◽  
...  
Keyword(s):  
Charge Density ◽  
Electron Density ◽  
Feasibility Study ◽  
Diamond Anvil Cell ◽  
Theoretical Calculations ◽  
Dynamic Structure ◽  
Opening Angle ◽  
High Symmetry ◽  
Diamond Anvil ◽  
Experimental Charge Density

X-ray diffraction studies of crystals under pressure and quantitative experimental charge density analysis are among the most demanding types of crystallographic research. A successful feasibility study of the electron density in the mineral grossular under 1 GPa pressure conducted at the CRISTAL beamline at the SOLEIL synchrotron is presented in this work. A single crystal was placed in a diamond anvil cell, but owing to its special design (wide opening angle), short synchrotron wavelength and the high symmetry of the crystal, data with high completeness and high resolution were collected. This allowed refinement of a full multipole model of experimental electron distribution. Results are consistent with the benchmark measurement conducted without a diamond-anvil cell and also with the literature describing investigations of similar structures. Results of theoretical calculations of electron density distribution on the basis of dynamic structure factors mimic experimental findings very well. Such studies allow for laboratory simulations of processes which take place in the Earth's mantle.

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