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Disordered materials

Total scattering or pair distribution function analysis (PDF) is an analytical technique that can provide structural information from disordered materials by using the complete powder XRD pattern. Both the Bragg scattering and the underlying diffuse scattering are determined. The pair distribution function technique is also known as total scattering analysis. From the Bragg peaks in an X-ray diffractogram the long range order of the atoms can be deduced. The short range order, i.e. the local atomic structure, is present in the broad, less well- defined features in the diffractogram. This local structure is described quantitatively by the atomic pair distribution function.

Applications of pair distribution function (PDF) analysis

Pair distribution function analysis is applied to the structural characterization of materials that are intrinsically disordered. Such materials can be amorphous, poorly crystalline, nano-crystalline or nano-structured. Typically, such samples are:

  • Nanopowders
  • Glasses
  • Polymers
  • Pharmaceutical ingredients
  • Liquids

The PDF function itself is also used by the pharmaceutical industry as a fingerprint for amorphous materials. Other attractive areas of solid state chemistry research for PDF analysis include the study of energy related materials: materials for solid oxide fuel cells (SOFC), magnetic materials, MOF’s, zeolites and Li-battery materials.

Pair distribution function (PDF) determination and analysis

From the measured X-ray diffractogram the so-called structure function is determined following initial basic data reduction steps. The radial atomic pair distribution function is then calculated by a Fourier transformation. The pair distribution function describes the probability of finding two atoms separated by a certain distance in the material under investigation. Software is then used to find the structural model that best fits the determined PDF function.

Requirements for pair distribution function (PDF) measurements

To obtain the desired spatial resolution for the local atomic structure, data acquisition for PDF analysis must be performed:

  • Up to diffraction angles as high as possible (large Q-range)
  • Using X-rays of short wavelength (high-energy radiation)
  • With very good counting statistics
  • With optimal background suppression.

Due to these demanding requirements, the technique until recently almost exclusively relied on the high-quality X-ray beams that are available at synchrotron radiation sources. In practice it is often difficult and time-consuming to get access to such large-scale facilities. It is therefore highly desirable and sometimes even required to perform pre-screening on candidate samples in the research laboratory ahead of time.

Malvern Panalytical solutions for pair distribution function (PDF) analysis in the lab

The Empyrean multi-purpose X-ray diffraction platform can be configured for total scattering experiments for PDF analysis.

The configuration uses:

  • Silver or molybdenum X-ray tube
  • Incident beam focusing mirrors or a slit collimation system
  • Capillary spinner
  • Hybrid pixel detector (GaliPIX3D), line detector (X’Celerator)
  • Anti-scatter kit for background suppression.

Much attention has been paid to achieve a clean and featureless background, which is essential for obtaining meaningful results on highly disordered or fully amorphous materials.

Experimental data obtained with Malvern Panalytical systems allow for comparison with synchrotron results. The measured raw data can be processed and further analyzed with PDF analysis software packages that are available as freeware. 

Empyrean Nano 版

Empyrean Nano 版

多功能 X 射线散射平台

更多细节
测量 分子量, 颗粒形状, 粒子大小, 比表面积, 蛋白质团聚, 蛋白质稳定性, 物相鉴定, 物相定量, 孔径分布
测角仪配置 Vertical goniometer, Θ-Θ
粒度范围 1 - 100 nm
技术类型 X 射线衍射 (XRD), X 射线散射

Empyrean

Empyrean

智能X射线衍射仪

更多细节
测量 晶体结构测定, 物相鉴定, 物相定量, 污染物检测与分析, 残余应力, 外延附生分析, 界面粗糙度, 织构分析, 3D 结构/成像, 倒易空间分析
测角仪配置 Vertical goniometer, Θ-Θ
粒度范围 1 - 100 nm
技术类型 X 射线衍射 (XRD)

Empyrean Nano 版

Empyrean Nano 版

多功能 X 射线散射平台

Empyrean

Empyrean

智能X射线衍射仪

更多细节 更多细节
测量 分子量, 颗粒形状, 粒子大小, 比表面积, 蛋白质团聚, 蛋白质稳定性, 物相鉴定, 物相定量, 孔径分布 晶体结构测定, 物相鉴定, 物相定量, 污染物检测与分析, 残余应力, 外延附生分析, 界面粗糙度, 织构分析, 3D 结构/成像, 倒易空间分析
测角仪配置 Vertical goniometer, Θ-Θ Vertical goniometer, Θ-Θ
粒度范围 1 - 100 nm 1 - 100 nm
技术类型 X 射线衍射 (XRD), X 射线散射 X 射线衍射 (XRD)

Empyrean Nano 版

Empyrean

Empyrean Nano 版 Empyrean

多功能 X 射线散射平台

智能X射线衍射仪

更多细节 更多细节
技术类型
X 射线衍射 (XRD)