Hydrogen Bonds in NH4F and NH4HF2Crystals. Comparison of Electron Density Distribution Obtained by X-ray Diffraction and by Quantum Chemistry

2000 ◽  
Vol 104 (46) ◽  
pp. 10901-10912 ◽  
Author(s):  
Sikko J. van Reeuwijk ◽  
Kai G. van Beek ◽  
Dirk Feil
Keyword(s):  
Hydrogen Bonds ◽  
Quantum Chemistry ◽  
Density Distribution ◽  
Electron Density ◽  
Electron Density Distribution ◽  
X Ray Diffraction ◽  
X Ray

Insight into the Electron Density Distribution in an O,N-Heterocyclic Stannylene by High-Resolution X-ray Diffraction Analysis

2019 ◽  
Vol 2019 (6) ◽  
pp. 875-884 ◽  
Author(s):  
Maxim G. Chegerev ◽  
Alexandr V. Piskunov ◽  
Kseniya V. Tsys ◽  
Andrey G. Starikov ◽  
Klaus Jurkschat ◽  
...  
Keyword(s):  
High Resolution ◽  
Density Distribution ◽  
Diffraction Analysis ◽  
Electron Density ◽  
Electron Density Distribution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Insight Into

Electron density distribution and Madelung potential in α-spodumene, LiAl(SiO3)2, from two-wavelength high-resolution X-ray diffraction data

1999 ◽  
Vol 55 (3) ◽  
pp. 273-284 ◽  
Author(s):  
Sandrine Kuntzinger ◽  
Nour Eddine Ghermani
Keyword(s):  
High Resolution ◽  
Density Distribution ◽  
Electron Density ◽  
Electron Density Distribution ◽  
Data Sets ◽  
X Ray Diffraction ◽  
Net Charge ◽  
X Ray ◽  
Madelung Potential ◽  
Net Charges

The electron density distribution in α-spodumene, LiAl(SiO3)2, was derived from high-resolution X-ray diffraction experiments. The results obtained from both Mo Kα- and Ag Kα-wavelength data sets are reported. The features of the Si—O and Al—O bonds are related to the geometrical parameters of the Si—O—Al and Si—O—Si bridges on the one hand and to the O...Li+ interaction on the other. Kappa refinements against the two data sets yielded almost the same net charges for the Si (+1.8 e) and O (−1.0 e) atoms in spodumene. However, the Al net charge obtained from the Ag Kα data (+1.9 e) is larger than the net charge derived from the Mo Kα data (+1.5 e). This difference correlates with a more contracted Al valence shell revealed by the shorter X-ray wavelength (κ = 1.4 for the Ag Kα data set). The derived net charges were used to calculate the Madelung potential at the spodumene atomic sites. The electrostatic energy for the chemical formula LiAl(SiO3)2 was −8.60 e2 Å−1 (−123.84 eV) from the net charges derived from the Ag Kα data and −6.97 e2 Å−1 (−100.37 eV) from the net charges derived from the Mo Kα data.

Electron density distribution of Ba1-xKxBiO3 (x = 0.43) by ultra-short-wavelength x-ray diffraction

2002 ◽  
Vol 14 (22) ◽  
pp. 5477-5484 ◽  
Author(s):  
Yasuhiko Takahashi ◽  
Xioali Ji ◽  
Taichiro Nishio ◽  
Hiromoto Uwe ◽  
Ken-ichi Ohshima
Keyword(s):  
Density Distribution ◽  
Electron Density ◽  
Short Wavelength ◽  
Electron Density Distribution ◽  
X Ray Diffraction ◽  
X Ray

Electron Density Distribution in LiB3O5 at 293 K

1997 ◽  
Vol 53 (6) ◽  
pp. 870-879 ◽  
Author(s):  
C. Le Hénaff ◽  
N. K. Hansen ◽  
J. Protas ◽  
G. Marnier
Keyword(s):  
Density Distribution ◽  
Electron Density ◽  
Electron Density Distribution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hartree Fock ◽  
Density Maps ◽  
Symmetry Constraints ◽  
Net Charges ◽  
Good Agreement

The electron density distribution in lithium triborate LiB3O5 has been studied at room temperature by X-ray diffraction using Ag K \alpha radiation up to 1.02 Å−1 [1439 unique reflections with I > 3\sigma(I)]. Conventional refinements with a free-atom model yield R(F) = 0.0223, wR(F) = 0.0299, S = 1.632. Atom charge refinements show that the lithium should be considered a monovalent ion. Multipolar refinements were undertaken up to fourth order, imposing local non-crystallographic symmetry constraints in order to avoid phase problems leading to meaningless multipole populations due to the non-centrosymmetry of the structure (space group: Pn a21). The residual indices decreased to: R(F) = 0.0147, wR(F) = 0.0193, S = 1.106. The net charges are in good agreement with what can be expected in borate chemistry. Deformation density maps are analysed in terms of \sigma and \pi bonding. The experimental electron distribution in the p z orbitals of triangular B atoms and surrounding O atoms has been analysed by introducing idealized hybridized states. In parallel, the electron density has been determined from ab initio Hartree–Fock calculations on fragments of the structure. Agreement with the X-ray determination is very good and confirms the nature of bonding in the crystal. The amount of transfer of \pi electrons from the oxygen to the triangular B atoms is estimated to be 0.22 electrons by theory.

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