Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Untangling unknown structures in the mix

06.11.2014

A combination of X-ray diffraction and computational techniques can determine unknown crystal structures in powder mixtures

The characterization of individual components in an unknown crystalline powder mixture is a challenge that has eluded scientists for many years. Now, A*STAR researchers have for the first time invented a methodology to accurately determine the crystal structures present in such mixtures1.


A new method that combines X-ray diffraction with computational analysis can be used to measure mixtures of unknown solids and identify their individual components.

© 2014 A*STAR Institute of Chemical and Engineering Sciences

Powder X-ray diffraction (PXRD) is a powerful tool used to determine the structure of crystalline solids. Every solid has its own unique crystal structure which, when hit by X-rays, produces a unique diffraction pattern — a ‘fingerprint’ from which the solid can then be identified and characterized through computational analysis.

However, traditional PXRD works best with pure single-component powders; mixed powders of unknown solids are far more difficult to analyze because the diffraction patterns overlap and are difficult to separate. Another complication is that individual solids can produce slightly different diffraction patterns depending on how the crystals are shaped and orientated in the powder samples.

Marc Garland and co-workers at the A*STAR Institute of Chemical and Engineering Sciences in Singapore have developed a new methodology, the PXRD-BTEM-Rietveld method, which combines two existing techniques to determine the individual crystal structures in a powder mixture.

“Many analytical problems in the chemical sciences involve mixtures of unknown solids,” explains Garland. “The extension of PXRD analysis to these mixtures opens up a myriad of new possibilities for the experimentalist because a purified single-component sample is no longer needed.”

First, Garland and his team used PXRD to obtain diffraction datasets from pre-prepared mixtures of several different powders. They then used their own algorithm, called band-target entropy minimization (BTEM), to sift through the entire dataset, looking for the simplest underlying patterns and to untangle overlapping diffraction patterns.

“BTEM is a blind separation technique,” explains Garland. “By searching for the simplest patterns — those with the smoothest profiles and the least signal disorder — we obtain accurate estimates of each pure component’s diffraction pattern.”

Garland and his team then used computational structure determination, including so-called Rietveld refinement, to obtain the crystal structures for each solid. This allowed the researchers to characterize the unknown components in the mixtures.

“One example of an application for our new technique could be investigating polymorphism in pharmaceuticals,” says Garland. “Each polymorphic pharmaceutical solid has a unique diffraction pattern resulting from its crystal structure, and it is incredibly important to the pharmaceutical industry to identify these from mixtures.”

The researchers plan to further refine their methodology, and hope to eliminate the problem of measuring irregularities due to crystal orientation.

Reference
Schreyer, M., Guo, L., Thirunahari, S., Gao, F. & Garland, M. Simultaneous determination of several crystal structures from powder mixtures: The combination of powder X-ray diffraction, band-target entropy minimization and Rietveld methods. Journal of Applied Crystallography 47, 659–667 (2014).

Associated links
A*STAR article

A*STAR Research | ResearchSEA
Further information:
http://www.researchsea.com

More articles from Physics and Astronomy:

nachricht A quantum walk of photons
24.05.2017 | Julius-Maximilians-Universität Würzburg

nachricht Scientists propose synestia, a new type of planetary object
23.05.2017 | University of California - Davis

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: A quantum walk of photons

Physicists from the University of Würzburg are capable of generating identical looking single light particles at the push of a button. Two new studies now demonstrate the potential this method holds.

The quantum computer has fuelled the imagination of scientists for decades: It is based on fundamentally different phenomena than a conventional computer....

Im Focus: Turmoil in sluggish electrons’ existence

An international team of physicists has monitored the scattering behaviour of electrons in a non-conducting material in real-time. Their insights could be beneficial for radiotherapy.

We can refer to electrons in non-conducting materials as ‘sluggish’. Typically, they remain fixed in a location, deep inside an atomic composite. It is hence...

Im Focus: Wafer-thin Magnetic Materials Developed for Future Quantum Technologies

Two-dimensional magnetic structures are regarded as a promising material for new types of data storage, since the magnetic properties of individual molecular building blocks can be investigated and modified. For the first time, researchers have now produced a wafer-thin ferrimagnet, in which molecules with different magnetic centers arrange themselves on a gold surface to form a checkerboard pattern. Scientists at the Swiss Nanoscience Institute at the University of Basel and the Paul Scherrer Institute published their findings in the journal Nature Communications.

Ferrimagnets are composed of two centers which are magnetized at different strengths and point in opposing directions. Two-dimensional, quasi-flat ferrimagnets...

Im Focus: World's thinnest hologram paves path to new 3-D world

Nano-hologram paves way for integration of 3-D holography into everyday electronics

An Australian-Chinese research team has created the world's thinnest hologram, paving the way towards the integration of 3D holography into everyday...

Im Focus: Using graphene to create quantum bits

In the race to produce a quantum computer, a number of projects are seeking a way to create quantum bits -- or qubits -- that are stable, meaning they are not much affected by changes in their environment. This normally needs highly nonlinear non-dissipative elements capable of functioning at very low temperatures.

In pursuit of this goal, researchers at EPFL's Laboratory of Photonics and Quantum Measurements LPQM (STI/SB), have investigated a nonlinear graphene-based...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

AWK Aachen Machine Tool Colloquium 2017: Internet of Production for Agile Enterprises

23.05.2017 | Event News

Dortmund MST Conference presents Individualized Healthcare Solutions with micro and nanotechnology

22.05.2017 | Event News

Innovation 4.0: Shaping a humane fourth industrial revolution

17.05.2017 | Event News

 
Latest News

Devils Hole: Ancient Traces of Climate History

24.05.2017 | Earth Sciences

Discovery of a Key Regulatory Gene in Cardiac Valve Formation

24.05.2017 | Life Sciences

A CLOUD of possibilities: Finding new therapies by combining drugs

24.05.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>