A Theoretical and Experimental Study of the Chemical Bonding in AgGaS2

1996 ◽  
Vol 453 ◽  
Author(s):  
Alessandra Continenza ◽  
Teresa M. de Pascale ◽  
Franco Meloni ◽  
Marina Serra ◽  
Ali Shaukat ◽  
...  
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Charge Density ◽  
Ab Initio ◽  
Chemical Bond ◽  
Chemical Bonding ◽  
X Ray ◽  
Electronic Distribution ◽  
D Orbitals

AbstractAgGaS2 is a technologically important semiconductor for its large birefringence coefficient. In this work we compare the theoretical ab-initio all-electron FLAPW results with very refined experimental data obtained with accurate X-ray analysis. In particular we focus our attention to the electronic distribution along the significative bonding directions connecting the three different atoms. Furthermore, the charge density contours around Ag provide a clear evidence of the contribution of its d orbitals to the chemical bond.

X-ray charge density study of chemical bonding in skutteruditeCoSb3

2007 ◽  
Vol 76 (6) ◽  
Author(s):  
Atsuko Ohno ◽  
Satoshi Sasaki ◽  
Eiji Nishibori ◽  
Shinobu Aoyagi ◽  
Makoto Sakata ◽  
...  
Keyword(s):  
Charge Density ◽  
Chemical Bonding ◽  
X Ray ◽  
Density Study

scholarly journals Ab initio random structure searching of organic molecular solids: assessment and validation against experimental data

2017 ◽  
Vol 19 (38) ◽  
pp. 25949-25960 ◽  
Author(s):  
Miri Zilka ◽  
Dmytro V. Dudenko ◽  
Colan E. Hughes ◽  
P. Andrew Williams ◽  
Simone Sturniolo ◽  
...  
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Crystal Structures ◽  
Mas Nmr ◽  
Molecular Solids ◽  
Random Structure ◽  
Aminobenzoic Acid ◽  
X Ray Diffraction ◽  
X Ray ◽  
Acid Comparison

The AIRSS method generates crystal structures for m-aminobenzoic acid; comparison is made to experimental powder X-ray diffraction and MAS NMR.

Phase transitions in perovskites near the tricritical point: an experimental study of KMn1–xCaxF3 and SrTiO3

2000 ◽  
Vol 64 (6) ◽  
pp. 971-982 ◽  
Author(s):  
M. C. Gallardo ◽  
F. J. Romero ◽  
S. A. Hayward ◽  
E. K. H. Salje ◽  
J. del Cerro
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Phase Transitions ◽  
Order Parameter ◽  
Tricritical Point ◽  
Mean Field ◽  
Calorimetric Data ◽  
X Ray ◽  
First Order ◽  
Field Behaviour

AbstractWe present experimental data for the Pm3m-I4/mcm phase transitions in the perovskite crystals KMn1-xCaxF3 and SrTiO3. Comparison of calorimetric data (latent heat and specific heat) with order parameter data (measured with X-ray rocking methods) indicates that these transitions follow mean-field behaviour, and may be described using Landau potentials where the free energy expansion includes terms up to Q6. This potential is characteristic of transitions close to the tricritical point. Comparison of the behaviour of SrTiO3 and KMnF3 indicates that KMnF3 is closer to the tricritical point; a small amount of substitution of Ca for Mn causes the transition to cross the tricritical point from first order to second order behaviour.

Zinc Substituted Hydroxyapatite – A Comparison of Modelling and Experimental Data

2008 ◽  
Vol 396-398 ◽  
pp. 729-732 ◽  
Author(s):  
Helen Chappell ◽  
David Shepherd ◽  
Serena Best
Keyword(s):  
Experimental Data ◽  
Experimental Study ◽  
Ab Initio ◽  
Formation Energy ◽  
Room Temperature ◽  
Lattice Parameter ◽  
Experimental Measurements ◽  
Type Ii ◽  
Substitution Site ◽  
Modelling Data

The effect of substitution of zinc into the hydroxyapatite lattice(ZnHA) was evaluated using experimental precipitation studies and with ab initio modelling data. When attempting to introduce zinc into the hydroxyapatite (HA) lattice not all of the zinc is substituted and ICP confirms its presence in the supernatant. Modelling suggests that this is likely to be because of the high formation energy introducing zinc into the pure hydroxyapatite lattice, 4.6 - 4.9eV. In the experimental study it was found that a maximum of 0.61wt% zinc could be substituted into the HA lattice at 10oC with less being substituted at room temperature »22oC. Experimental measurements revealed that the presence of zinc in the lattice decreased the a-lattice parameter and increased the c-lattice parameter. Modelling showed that this was likely to be caused by the movement of the hydroxyl ions away from the c-axis, towards the zinc atoms which were substituted in calcium type II positions. The type II position was shown to be the most stable substitution site.

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.

Experimental study of X-ray charge density and the selection of reference points for a source function in η6-(2-methyl-1,4-dihydro-2H-3,1-benzoxazine)tricarbonylchromium(0)

2019 ◽  
Vol 29 (3) ◽  
pp. 346-348 ◽  
Author(s):  
Georgy K. Fukin ◽  
Anton V. Cherkasov ◽  
Roman V. Rumyantcev ◽  
Natalia Yu. Grishina ◽  
Elena V. Sazonova ◽  
...  
Keyword(s):  
Experimental Study ◽  
Charge Density ◽  
Source Function ◽  
Reference Points ◽  
X Ray ◽  
Selection Of

The Chemical Bond in Carbonyl and Sulfinyl Groups Studied by Soft X-ray Spectroscopy and ab Initio Calculations

ChemPhysChem ◽  
2012 ◽  
Vol 13 (13) ◽  
pp. 3106-3111 ◽  
Author(s):  
Kaan Atak ◽  
Nicholas Engel ◽  
Kathrin M. Lange ◽  
Ronny Golnak ◽  
Malte Gotz ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Chemical Bond ◽  
X Ray
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