On the estimation of atomic charges by the X-ray method for some oxides and silicates

Sasaki, Satoshi; Fujino, Kiyoshi; Takéuchi, Yoshio; Sadanaga, Ryôichi

doi:10.1107/s0567739480001908

Cited by 141 publications

(79 citation statements)

References 6 publications

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“…Atomic charges derived from diffraction data by some current methods appear to be too large, based on the considerations of the ionic pair model (see e.g. Sasaki et al 1980). It would be a worthwhile exercise to apply Hirshfeld's partitioning scheme to the data sets to test whether silicon and oxygen are charged as highly as the original results suggest.…”

Section: Discussionmentioning

confidence: 99%

Atomic Charges and Electron Density Partitioning

Maslen¹,

Spackman²

1985

Aust. J. Phys.

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Aust. J. Phys., 1985, 38, 273-87 Atomic charges are derived from two dissimilar methods of partitioning the electron density of diatomic molecules. The results given by both methods are similar, with the exception of those for molecules containing lithium; factors responsible for this discrepancy are explored. The charges derived are correlated closely with electronegativity differences and with dipole moments. They follow chemically sensible trends and have reasonable magnitudes. The partitioning methods used in the derivation can also be applied to the analysis of diffraction data for crystalline solids.

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Section: Discussionmentioning

confidence: 99%

Atomic Charges and Electron Density Partitioning

Maslen¹,

Spackman²

1985

Aust. J. Phys.

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“…More meaningful charge values are obtained from spherical charge integrations, Z(r), around the atomic sites. These calculations were carried out by Fourier summations and series truncation error corrections as outlined by Sasaki et al (1980) using the computer program CHACLI (Kirfel, 1983). Taking the absolute minima of the radial charge-density distributions, dZadr, as de®ning ionic radii and observing the neutrality constraint, one obtains Si 3.25+ O 2 1.62À and Si 2.52+ O 2 1.26À depending on whether the estimate is based on dZadr of Si or O, respectively.…”

Section: Structure Refinementsmentioning

confidence: 99%

Electron-density distribution in stishovite, SiO₂: a new high-energy synchrotron-radiation study

et al. 2001

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The electron-density distribution of the high-pressure polymorph of SiO 2 , stishovite [a = 4.177 (1) , c = 2.6655 (5) A Ê , space group P4 2 amnm, Z = 2], has been redetermined by single-crystal diffractometry using synchrotron radiation of 100.42 and 30.99 keV, respectively, in order to obtain essentially absorptionand extinction-free data. Room-temperature diffraction experiments on two samples of irregular shape were carried out on two different diffractometers installed at HASYLAB/DESY, Hamburg, Germany. The structure re®nement on the high-energy data converged at R(F ) = 0.0047, wR(F ) = 0.0038, GoF = 0.78, for a multipole model with neutral atoms and multipole expansions up to seventh order. For each atom, the radial expansion coef®cients of the multipole orders (l > 0) were constrained to a common value. The absence of extinction was indicated by a re®ned correction parameter equalling zero within error limit. The excellent quality of the data is also illustrated by a high-order (HO) re®nement (s > 0.7 A Ê À1 ) yielding R(F ) = 0.0060, wR(F) = 0.0048, GoF = 0.85. Both static deformation electron-density distribution and structure amplitudes compare well with corresponding results obtained from band-structure calculations using the linearized-augmented-plane-wave (LAPW) method. Ensuing topological analysis of the total model electron density distribution revealed bond critical point properties for the two unique SiÐO bonds, indicating a predominantly closed-shell interaction mixed with a signi®cant shared interaction contribution that decreases with increasing interatomic distance. Calculation of atomic basins yielded charges of +3.39 e and À1.69 e for Si and O, respectively, in good agreement with the theoretically calculated values of +3.30 e and À1.65 e. The volumina of the Si and O basins are 2.32 and 10.48 A Ê 3 , corresponding to spheres with radii of 0.82 and 1.36 A Ê , respectively. The results also conform well with correlations between bond length and bond critical point properties reported in the literature for geometry-optimized hydroxyacid molecules. Estimates of the Si cation electronegativity indicate that the change of Si coordination by oxygen from 4 to 6 is accompanied by an increase of the ionicity of the SiÐO bond of about 7%.

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“…In addition to the atomic coordinates and thermal parameters, isotropic extinction parameters (Zachariasen, 1967;Coppens & Hamilton, 1970;Becker & Coppens, 1974) and occupancies of valence electrons were simultaneously refined in the final stages; the least-squares program EARTH (Sasaki et al, 1980) which is a modified version of LINUS (Coppens & Hamilton, 1970) was used. The least-squares refinement converged to R = 0.0277 (R w = 0.0280, where w = 1) for a-CozSiO4, and R = 0.0289 (R w = 0.0310) Tables 2 and 3, respectively.…”

Section: P22mentioning

confidence: 99%

Structures and electron distributions of α-Co₂SiO₄ and α-Ni₂SiO₄ (olivine structure)

Tamada¹,

Fujino²,

Sasaki³

1983

Acta Crystallogr B Struct Sci

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The single-crystal X-ray study of tx-Co2SiO 4 and ct-Ni2SiO4 (olivine structure) has revealed the structural characteristics, the net atomic charges, and the distributions of the aspherical electron density around the Co and Ni atoms. The Si atoms, occupying tetrahedral sites, are less ionic than octahedral transition-metal ions such as Co 2÷ and Ni 2+. A previous report that transition-metal ions are less ionic than the Mg 2÷ ion in the olivine structure is supported by this study.

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On the estimation of atomic charges by the X-ray method for some oxides and silicates

Abstract: Based on accurate X-ray diffraction intensity data collected from spherically shaped single crystals, net atomic charges and electron density distributions have been studied for MnO, Mn2SiO 4,

Cited by 141 publications

References 6 publications

Atomic Charges and Electron Density Partitioning

Atomic Charges and Electron Density Partitioning

Electron-density distribution in stishovite, SiO₂: a new high-energy synchrotron-radiation study

Structures and electron distributions of α-Co₂SiO₄ and α-Ni₂SiO₄ (olivine structure)

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On the estimation of atomic charges by the X-ray method for some oxides and silicates

Abstract: Based on accurate X-ray diffraction intensity data collected from spherically shaped single crystals, net atomic charges and electron density distributions have been studied for MnO, Mn2SiO 4,

Cited by 141 publications

References 6 publications

Atomic Charges and Electron Density Partitioning

Atomic Charges and Electron Density Partitioning

Electron-density distribution in stishovite, SiO2: a new high-energy synchrotron-radiation study

Structures and electron distributions of α-Co2SiO4 and α-Ni2SiO4 (olivine structure)

Contact Info

Product

Resources

About

Electron-density distribution in stishovite, SiO₂: a new high-energy synchrotron-radiation study

Structures and electron distributions of α-Co₂SiO₄ and α-Ni₂SiO₄ (olivine structure)