A Comprehensive Study of Ca9Tb(PO4)7 and Ca9Ho(PO4)7 Doped β-Tricalcium Phosphates: Ab initio Crystal Structure Solution, Rietveld Analysis, and Dielectric Properties

2021 ◽  
Author(s):  
Rosanna Rizzi ◽  
Francesco Capitelli ◽  
Bogdan I. Lazoryak ◽  
Vladimir A. Morozov ◽  
Fabio Piccinelli ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Dielectric Properties ◽  
Ab Initio ◽  
Rietveld Analysis ◽  
Structure Solution ◽  
Tricalcium Phosphates ◽  
Comprehensive Study

The revenge of the Patterson methods. II. Substructure applications

2007 ◽  
Vol 40 (2) ◽  
pp. 211-217 ◽  
Author(s):  
Maria Cristina Burla ◽  
Rocco Caliandro ◽  
Benedetta Carrozzini ◽  
Giovanni Luca Cascarano ◽  
Liberato De Caro ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ab Initio ◽  
Electron Density ◽  
Direct Methods ◽  
Large Set ◽  
Common Belief ◽  
Anomalous Diffraction ◽  
Density Maps ◽  
Structure Solution ◽  
The Common

The Patterson techniques, recently developed by the same authors for theab initiocrystal structure solution of proteins, have been applied to single and multiple anomalous diffraction (SAD and MAD) data to find the substructure of the anomalous scatterers. An automatic procedure has been applied to a large set of test structures, some of which were originally solved with remarkable difficulty. In all cases, the procedure automatically leads to interpretable electron density maps. Patterson techniques have been compared with direct methods; the former seem to be more efficient than the latter, so confirming the results obtained forab initiophasing, and disproving the common belief that they could only be applied to determine large equal-atom substructures with difficulty.

Ab initio crystal structure solution of the novel intermetallic compound Nd3(Fe,Ti)29

1996 ◽  
Vol 234 (1) ◽  
pp. 62-66 ◽  
Author(s):  
V. Psycharis ◽  
O. Kalogirou ◽  
D. Niarchos ◽  
M. Gjoka
Keyword(s):  
Crystal Structure ◽  
Intermetallic Compound ◽  
Ab Initio ◽  
The Novel ◽  
Structure Solution

Crystal structure determination and refinementviaSIR2014

2015 ◽  
Vol 48 (1) ◽  
pp. 306-309 ◽  
Author(s):  
Maria Cristina Burla ◽  
Rocco Caliandro ◽  
Benedetta Carrozzini ◽  
Giovanni Luca Cascarano ◽  
Corrado Cuocci ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ab Initio ◽  
Structure Refinement ◽  
Three Dimensional ◽  
Direct Methods ◽  
Molecular Replacement ◽  
Dimensional Electron ◽  
Large Structures ◽  
Density Maps ◽  
Structure Solution

SIR2014is the latest program of theSIRsuite for crystal structure solution of small, medium and large structures. A variety of phasing algorithms have been implemented, bothab initio(standard or modern direct methods, Patterson techniques,Vive la Différence) and non-ab initio(simulated annealing, molecular replacement). The program contains tools for crystal structure refinement and for the study of three-dimensional electron-density mapsviasuitable viewers.

Structure of LaTi2Al9O19 and reanalysis of the crystal structure of La3Ti5Al15O37

2011 ◽  
Vol 67 (6) ◽  
pp. 455-460 ◽  
Author(s):  
Marta Kasunič ◽  
Anton Meden ◽  
Srečo D. Škapin ◽  
Danilo Suvorov ◽  
Amalija Golobič
Keyword(s):  
Crystal Structure ◽  
Dielectric Properties ◽  
Ab Initio ◽  
Powder Diffraction ◽  
Complex Structure ◽  
Bond Valence ◽  
X Ray ◽  
Bond Valence Sum

The non-perovskite compound LaTi2Al9O19 was synthesized and structurally characterized by conventional X-ray powder diffraction and shown to be isostructural with SrTi3Al8O19, as confirmed by bond-valence sum calculations. The dielectric properties of LaTi2Al9O19 at 1 MHz were measured. The crystal structure of La3Ti5Al15O37, which is referred to as the most complex structure solved ab initio from X-ray powder diffraction (XRPD) to date, is shown to be incorrect.

Phasing methods for powder data

2013 ◽  
Author(s):  
Carmelo Giacovazzo
Keyword(s):  
Crystal Structure ◽  
Single Crystal ◽  
Ab Initio ◽  
Powder Diffraction ◽  
Powder Pattern ◽  
Inorganic Crystal Structure Database ◽  
Space Group ◽  
Structure Solution ◽  
Group A ◽  
Basic Features

Powder diffractometry plays (and will probably continue to play in the near future) a central role in research and technology, because it allows us to investigate materials which are not available as a single crystal of adequate size and quality. Therefore, recently, much effort has been devoted to the development of powder diffraction. Improvements include the design of better instruments (e.g. optimized synchrotron radiation lines, time-of-flight technology at pulsed neutron sources, optics, generators, detectors), as well as more sophisticated methods for data analysis. As a result, in favourable cases, high quality powder patterns of proteins may be collected which contain sufficient information to allow identification of the unit cell and of the space group, a result unthinkable 30 years ago. This has opened the way for qualitative analysis and study of the polymorphism of macromolecules (Margiolaki et al., 2005; Collings et al., 2010). Advances in the experimental and the theoretical aspects of powder crystallography have been able to reduce losses of information from a powder pattern with respect to single crystal data, and have made ab initio crystal structure solution from powder experiments possible. The reader may deduce the increasing popularity of powder techniques from: (i) Table 1.11, where, among the CSD (Cambridge Structural Database), entries on 1 January 2012, 2354 powder diffraction studies were counted; (ii) Figure 12.1, where the cumulative statistics (up to the year 2006) on the number of structures solved via powder diffraction data is shown (SDPD database); (iii) Figure 12.2, where the statistics on the number of studies in the ICDD (Inorganic Crystal Structure Database) (to the year 2005) for different types of data is given. For the powder case, 21 472 cases are counted for which powder data have been used, mostly for refinement purposes. In this chapter, we will neglect experimental aspects, unless unrelated to the phasing problem. We will describe in Sections 12.2 to 12.5, the basic features of powder pattern diagrams, and in Sections 12.6 and 12.7, the procedures for full pattern indexing and space group determination. Ab initio phasing will be treated in Section 12.8 and non-ab initio methods in Section 12.9. The combination of anomalous dispersion techniques with powder methods is postponed to Section 15.9.

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