X-ray diffraction (XRD)

Definition

X-ray diffraction (XRD) is a powerful analytical technique used to study the structure of crystalline materials by measuring the angles and intensities of X-rays scattered by the sample. This method allows researchers to determine the arrangement of atoms within a crystal, providing insights into its properties and behaviors. The relationship between the X-ray wavelength and the angle of diffraction is governed by fundamental principles, including Bragg's law, which establishes the conditions for constructive interference in the scattered X-rays.

5 Must Know Facts For Your Next Test

1. XRD is widely used to identify unknown crystalline materials by comparing the obtained diffraction patterns with standard reference patterns.
2. The intensity and position of peaks in an XRD pattern provide information about the crystallite size, shape, and internal strain of the material.
3. XRD can be performed in various configurations, such as powder diffraction for bulk samples or single-crystal diffraction for precise structural determination.
4. The technique is highly sensitive and can detect even slight changes in crystal structure, making it valuable for studying phase transitions and polymorphism.
5. Sample preparation for XRD is crucial; poorly prepared samples can lead to inaccurate results, emphasizing the need for uniform particle size and optimal alignment.

Review Questions

• How does Bragg's Law relate to x-ray diffraction and what are its implications for determining crystal structures?
  • Bragg's Law establishes the conditions necessary for constructive interference of X-rays scattered by a crystal. It is expressed as $$n\lambda = 2d\sin\theta$$, where $$\lambda$$ is the wavelength of the X-ray, $$d$$ is the distance between atomic planes, and $$\theta$$ is the angle of diffraction. This relationship allows researchers to deduce information about the spacing of planes within a crystal and ultimately leads to insights about its overall atomic arrangement.
• Discuss how x-ray diffraction can be applied to analyze material properties and what information can be derived from its patterns.
  • X-ray diffraction is crucial for characterizing materials because it provides detailed information about their crystalline structure. By analyzing peak positions and intensities in an XRD pattern, researchers can determine parameters like unit cell dimensions, crystallite size, and phase composition. Additionally, changes in peak profiles can reveal internal strain or defects within a crystal, contributing to a comprehensive understanding of material properties.
• Evaluate the impact of sample preparation on x-ray diffraction results and how this might affect interpretations in crystallography.
  • Sample preparation plays a vital role in x-ray diffraction as poorly prepared samples can lead to misleading or inaccurate results. Factors such as particle size, homogeneity, and alignment greatly influence diffraction patterns. If samples are not uniformly sized or are poorly oriented, significant peaks may be absent or diminished, complicating analysis. Consequently, understanding how sample quality affects diffraction outcomes is essential for accurate interpretation in crystallography and for deriving reliable conclusions about material properties.

Related terms

Bragg's Law: A fundamental equation that relates the wavelength of X-rays to the angle of diffraction and the spacing between atomic planes in a crystal, given by the formula: $$n\lambda = 2d\sin\theta$$.

Crystal Lattice: The ordered, repeating arrangement of atoms or molecules in a crystalline solid, which defines its geometric structure and symmetry.

Reciprocal Lattice: A conceptual lattice used in crystallography to describe the spatial frequencies of the wave vectors associated with diffracted waves, essential for understanding diffraction patterns.