Topochemical Rationalization of the Solid-State Polymerization Reaction of Sodium Chloroacetate:  Structure Determination from Powder Diffraction Data by the Monte Carlo Method

Elizabé, Laurent; Kariuki, Benson M.; Harris, Kenneth D. M.; Tremayne, Maryjane; Epple, Matthias; Thomas, John Meurig

doi:10.1021/jp9712563

Cited by 41 publications

(30 citation statements)

References 29 publications

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“…The crystal structures of 3-chloro-trans-cinnamic acid (Kariuki et al, 1996), the and phases of l-glutamic acid , and the and phases of AIGH (Karfunkel et al, 1996) have been chosen as representatives of such systems. Sodium chloroacetate (Elizabe Â et al, 1997) is an example of a simple salt, which illustrates the applicability of our approach to structures with more than one molecular fragment in the asymmetric unit. The last two structures, cimetidine (Cernik et al, 1991) and Ph 2 P(O)±(CH 2 ) 7 ±P(O)Ph 2 (Kariuki, Calcagno et al, 1999), are two of the most complex molecular crystal structures solved from powder X-ray diffraction patterns so far.…”

Section: Structures Studiedmentioning

confidence: 84%

PowderSolve– a complete package for crystal structure solution from powder diffraction patterns

et al. 1999

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Powder diffraction techniques are becoming increasingly popular as tools for the determination of crystal structures. The authors of this paper have developed a software package, named PowderSolve, to solve crystal structures from experimental powder diffraction patterns and have applied this package to solve the crystal structures of organic compounds with up to 18 variable degrees of freedom (de®ned in terms of the positions, orientations, and internal torsions of the molecular fragments in the asymmetric unit). The package employs a combination of simulated annealing and rigid-body Rietveld re®nement techniques to maximize the agreement between calculated and experimental powder diffraction patterns. The agreement is measured by a full-pro®le comparison (using the R factor R wp ). As an additional check at the end of the structure solution process, accurate force-®eld energies may be used to con®rm the stability of the proposed structure solutions. To generate the calculated powder diffraction pattern, lattice parameters, peak shape parameters and background parameters must be determined accurately before proceeding with the structure solution calculations. For this purpose, a novel variant of the Pawley algorithm is proposed, which avoids the instabilities of the original Pawley method. The successful application and performance of PowderSolve for crystal structure solution of 14 organic compounds of differing complexity are discussed.

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Section: Structures Studiedmentioning

confidence: 84%

PowderSolve– a complete package for crystal structure solution from powder diffraction patterns

et al. 1999

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“…by limiting the number of internal degrees of freedom). The factors governing the choice of structural fragment are analogous to those discussed previously Elizabe Â et al, 1997) in the context of the Monte Carlo technique for structure solution.…”

Section: The Structural Fragmentmentioning

confidence: 96%

“…Initial work on direct-space structure solution focused on the development of Monte Carlo (Harris et al, 1994;Kariuki et al, 1996;Tremayne et al, 1996a,b;Ramprasad et al, 1995;Elizabe Â et al, 1997;Tremayne, Kariuki, Harris, Shankland & Knight, 1997) and simulated annealing (Newsam et al, 1992;Andreev et al, 1996Andreev et al, , 1997 methods for exploring the R wp (X) hypersurface. In the present paper, we describe a method for`direct-space' structure solution based on the application of a genetic algorithm to explore the R wp (X) hypersurface.…”

Section: The`direct-space' Strategymentioning

confidence: 99%

The Genetic Algorithm: Foundations and Apllications in Structure Solution from Powder Diffraction Data

Harris

Johnston²,

Kariuki³

1998

Acta Cryst Sect A

206

111

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Recently, new methods based on the use of genetic algorithms have been explored and developed for solving crystal structures directly from powder diffraction data. In implementing genetic algorithms in such applications, several different aspects of the technique and strategy are open to optimization, leading to a versatile and powerful approach. In this paper, the fundamental concepts underlying genetic algorithms are discussed and the implementation of the genetic algorithm for structure solution from powder diffraction data is described. The opportunities, scope and potential for future developments in the foundations and applications of genetic algorithms in this ®eld are highlighted. The genetic algorithm approach adopts the`direct-space' philosophy for structure solution, with trial structures generated independently of the experimental diffraction data and the quality of each structure assessed by comparing the calculated and experimental powder diffraction patterns; in this work, this comparison is made using the pro®le R factor R wp . In the genetic algorithm, a population of trial structures is allowed to evolve subject to well de®ned rules governing mating, mutation and`natural selection'. The`®tness' of each structure in the population is a function of its pro®le R factor. The successful application of the genetic algorithm approach for structure solution of molecular crystals from powder diffraction data is demonstrated with examples of previously known and previously unknown structures.

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“…Therefore, this polymer is used extensively in medical applications such as drug delivery and resorbable implants 10) and has been studied in depth in the 1990s [11][12][13][14][15][16][17][18][19][20] . PGA can be produced via the following exothermic solid-state polycondensation reaction of sodium chloroacetate between 373 and 473 K:…”

Section: Introductionmentioning

confidence: 99%

Preparation and In Vivo Study of Porous Titanium–Polyglycolide Composite

et al. 2016

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Porous materials show low Young s moduli and excellent bonding to living bone. However, the strength of such materials is often insufcient in the initial stage of implantation. Thus, the objective of this study was to increase the strength of porous titanium by lling the pores with polyglycolide (PGA), a biodegradable plastic. PGA powder was prepared via the thermal decomposition of sodium chloroacetate at 433 K. The PGA was then introduced into the pores of porous Ti (porosity: 60%) using two methods: (i) centrifugal packing and heating and (ii) heat injection. In the latter method, almost all pores were lled by PGA; the lling fraction was measured to be 65-85% regardless of the injection temperature. When the pores in the porous Ti were lled with PGA, the compressive strength increased drastically from 40 to 100 MPa. The increased strength is comparable to that of cortical bone. In addition, the strength increased with increasing injection temperature. In an animal test, unfavourable autopsy ndings, such as suppuration, bleeding, and hyperplasia of the connective tissue, could not be con rmed in rats and no bone was observed in the pores of the Ti-PGA composite. Decomposition of PGA lowered the surrounding pH, it was found to inhibit bone formation in the pores of the porous Ti. It is important to control the decomposition rate of PGA.

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Topochemical Rationalization of the Solid-State Polymerization Reaction of Sodium Chloroacetate: Structure Determination from Powder Diffraction Data by the Monte Carlo Method

Cited by 41 publications

References 29 publications

PowderSolve– a complete package for crystal structure solution from powder diffraction patterns

PowderSolve– a complete package for crystal structure solution from powder diffraction patterns

The Genetic Algorithm: Foundations and Apllications in Structure Solution from Powder Diffraction Data

Preparation and In Vivo Study of Porous Titanium–Polyglycolide Composite

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