DevelopingWinXPRO: a software for determination of the multipole-model-based properties of crystals

2014 ◽  
Vol 47 (6) ◽  
pp. 2086-2089 ◽  
Author(s):  
Adam I. Stash ◽  
Vladimir G. Tsirelson
Keyword(s):  
Computer Program ◽  
Electron Density ◽  
Density Functional ◽  
Atomic Displacement ◽  
Program Package ◽  
The Other ◽  
Output Data ◽  
Crystal Properties ◽  
Experimental Electron Density

The new release of the computer program packageWinXPRO v.3xfor determination of the crystal properties from parameters of the multipole-modeled experimental electron density and anharmonic atomic displacement coefficients is described. The set of properties is significantly extended by using the density functional and information theories. In addition, a built-in multi-functional viewer and programs to display the output data, including the mapping of the chosen functional bonding descriptors onto surfaces of the other properties, are included.

ChemInform Abstract: EXPERIMENTAL ELECTRON DENSITY DETERMINATION OF μ-METHYLENE COMPLEXES OF THE DIMETALLOCYCLOPROPANE TYPE

1982 ◽  
Vol 13 (4) ◽  
Author(s):  
D. A. CLEMENTE ◽  
B. REES ◽  
G. BANDOLI ◽  
M. CINGI BIAGINI ◽  
B. REITER ◽  
...  
Keyword(s):  
Electron Density ◽  
Density Determination ◽  
Experimental Electron Density

Experimental electron density study of ethylene oxide at 100 K

2008 ◽  
Vol 64 (3) ◽  
pp. 397-400 ◽  
Author(s):  
Simon Grabowsky ◽  
Manuela Weber ◽  
Jürgen Buschmann ◽  
Peter Luger
Keyword(s):  
Ethylene Oxide ◽  
Electron Density ◽  
Density Functional ◽  
High Strain ◽  
Membered Ring ◽  
Topological Properties ◽  
X Ray ◽  
Multipole Refinement ◽  
Experimental Electron Density ◽  
Density Study

The experimental electron density of ethylene oxide was derived from a multipole refinement of 100 K X-ray data and complemented by density-functional calculations at experimental and optimized geometry. Atomic and bond-topological properties were derived using the atoms-in-molecules (AIM) formalism. The high strain in the three-membered ring molecule is mainly expressed by the high ellipticities of the three bonds in this ring, while the bond paths are only slightly bent for the C—C bond, but are virtually straight for the C—O bond.

scholarly journals Quantum pressure focusing in solids: a reconstruction from experimental electron density

2019 ◽  
Vol 75 (2) ◽  
pp. 201-209 ◽  
Author(s):  
Vladimir G. Tsirelson ◽  
Adam I. Stash ◽  
Ilya V. Tokatly
Keyword(s):  
Density Functional Theory ◽  
Electron Density ◽  
Density Functional ◽  
Electron Shell ◽  
Correlation Effects ◽  
Functional Theory ◽  
Quantum Electron ◽  
The Density Functional Theory ◽  
Bonding Mechanisms ◽  
Experimental Electron Density

Here an approach is presented for reconstructing the distribution of electronic internal quantum pressure in the electronic continuum of solids from the experimental electron density. Using the formalism of the density functional theory, the spatial inner-crystal map of the quantum pressure is obtained. The results are visualized via the indicator of quantum pressure focusing (IQPF) which reveals the regions where the pressure is concentrated or depleted due to quantum effects. IQPF contains all quantum electron-shell structure-forming contributions resulting from kinetic, exchange and correlation effects, and presents a clear picture of the chemical bond features in crystals with different type of bonding mechanisms.

Bio-PIXE AT THE TAKIZAWA FACILITY (Bio-PIXE WITH A BABY CYCLOTRON)

1992 ◽  
Vol 02 (03) ◽  
pp. 325-330 ◽  
Author(s):  
K. SERA ◽  
T. YANAGISAWA ◽  
H. TSUNODA ◽  
S. FUTATSUGAWA ◽  
S. HATAKEYAMA ◽  
...  
Keyword(s):  
Data Analysis ◽  
Computer Program ◽  
Simultaneous Determination ◽  
Spectrum Analysis ◽  
The Other ◽  
Personal Computers ◽  
Measuring System ◽  
X Ray ◽  
Spectral Fitting

For the developement of bio-PIXE, two problems remain to be solved; one in accelerator availability and the other in data analysis. To improve the former, a method of applying baby cyclotrons to PIXE has been developed. To solve the latter, the computer program SAPIX for x-ray spectrum analysis ,which runs on ordinary personal computers and is fairly easy to operate has been developed. Examples of spectral fitting by the SAPIX and a description of the program are given. Further, the two-detector measuring system which we have employed for the simultaneous determination of all elements is reported.

Determination of covalent bond orders and atomic valence indices using topological features of the experimental electron density

2007 ◽  
Vol 63 (1) ◽  
pp. 142-150 ◽  
Author(s):  
Vladimir G. Tsirelson ◽  
Ekaterina V. Bartashevich ◽  
Adam I. Stash ◽  
Vladimir A. Potemkin
Keyword(s):  
Electron Density ◽  
Reasonable Agreement ◽  
Covalent Bond ◽  
Bond Orders ◽  
Orbital Theory ◽  
Topological Features ◽  
Experimental Electron Density ◽  
Atomic Valence

We present an approach for the determination of covalent bond orders from the experimental electron density and its derivatives at the bond critical points. An application of this method to a series of organic compounds has shown that it provides a bonding quantification that is in reasonable agreement with that obtained by orbital theory. The `experimental' atomic valence indices are also defined and their significance for the characterization of chemical problems is discussed.

scholarly journals Experimental and theoretical characterization of the Zn—Zn bond in [Zn2(η5-C5Me5)2]

2007 ◽  
Vol 63 (6) ◽  
pp. 862-868 ◽  
Author(s):  
Juan F. Van der Maelen ◽  
Enrique Gutiérrez-Puebla ◽  
Ángeles Monge ◽  
Santiago García-Granda ◽  
Irene Resa ◽  
...  
Keyword(s):  
Electron Density ◽  
Density Functional ◽  
Topological Analysis ◽  
Open Shell ◽  
Synchrotron Diffraction ◽  
Functional Theory ◽  
Metal Metal ◽  
Moller Plesset ◽  
Experimental Electron Density

The existence and characterization of a bond between the Zn atoms in the recently synthesized complex [Zn2(η5-C5Me5)2], as well as between Zn and ligand C atoms is firmly based on neutron diffraction and low-temperature X-ray synchrotron diffraction experiments. The multipolar analysis of the experimental electron density and its topological analysis by means of the `Atoms in Molecules' (AIM) approach reveals details of the Zn—Zn bond, such as its open-shell intermediate character (the results are consistent with a typical metal–metal single bond), as well as many other topological properties of the compound. Experimental results are also compared with theoretical ab initio calculations of the DFT (density functional theory) and MP2 (Møller-Plesset perturbation theory) electron densities, giving a coherent view of the bonding in the complex. For instance, charges calculated from the AIM approach applied to the atomic basin of each Zn atom are, on average, +0.72 e from both the experimental and the theoretical electron density, showing a moderate charge transfer from the metal, confirmed by the calculated topological indexes.

scholarly journals CRYSTALSenhancements: asymmetric restraints

2012 ◽  
Vol 45 (5) ◽  
pp. 1057-1060 ◽  
Author(s):  
Richard Ian Cooper ◽  
Andrea Thorn ◽  
David John Watkin
Keyword(s):  
Atomic Displacement ◽  
The Other ◽  
Distance Restraint ◽  
Atomic Displacement Parameter ◽  
Displacement Parameter

The traditional Waser distance restraint, the rigid-bond restraint and atomic displacement parameter (ADP) similarity restraints have an equal influence on both atoms involved in the restraint. This may be inappropriate in cases where it can reasonably be expected that the precision of the determination of the positional parameters and ADPs is not equal,e.g.towards the extremities of a librating structure or where one atom is a significantly stronger scatterer than the other. In these cases, the traditional restraint feeds information from the poorly defined atom to the better defined atom, with the possibility that its characteristics become degraded. The modified restraint described here feeds information from the better defined atom to the more poorly defined atom with minimal feedback.

On the transferability of QTAIMC descriptors derived from X-ray diffraction data and DFT calculations: substituted hydropyrimidine derivatives

2011 ◽  
Vol 67 (5) ◽  
pp. 425-436 ◽  
Author(s):  
A. A. Rykounov ◽  
A. I. Stash ◽  
V. V. Zhurov ◽  
E. A. Zhurova ◽  
A. A. Pinkerton ◽  
...  
Keyword(s):  
Electron Density ◽  
Density Functional ◽  
Molecular Structures ◽  
X Ray Diffraction ◽  
Covalent Bonds ◽  
Functional Theory ◽  
X Ray ◽  
Biginelli Compounds ◽  
Empirical Corrections

The combined study of electron-density features in three substituted hydropyrimidines of the Biginelli compound family has been fulfilled. Results of the low-temperature X-ray diffraction measurements and density functional theory (DFT) B3LYP/6-311++G** calculations of these compounds are described. The experimentally derived atomic and bonding characteristics determined within the quantum-topological theory of atoms in molecules and crystals (QTAIMC) were demonstrated to be fully transferable within chemically similar structures such as the Biginelli compounds. However, for certain covalent bonds they differ significantly from the theoretical results because of insufficient flexibility of the atom-centered multipole electron density model. It was concluded that currently analysis of the theoretical electron density provides a more reliable basis for the determination of the transferability of QTAIMC descriptors for molecular structures. Empirical corrections making the experimentally derived QTAIMC bond descriptors more transferable are proposed.

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