How to Determine the Unit Cell Type From the XRD Data?

In summary, Tom is seeking help in determining the density of his sample by finding the lattice parameters through XRD data. He is unsure of the crystallographic system and is looking for a way to determine the type of unit cell his sample has. He mentions using GSAS II and asks for a good source to study this topic, as the textbook he has and a Google search have not been helpful. He then shares a link he found through a quick Google search and suggests trying a scholar search for more reliable sources.
  • #1
Dario56
290
45
Hey guys,

I got an XRD data for my sample and want to determine its density. This requires finding lattice parameters. However, I'm not certain about the crystallographic system of my sample. How can I determine the type of the unit cell my sample has from XRD data (I can use GSAS II if needed)? Do you know a good source where I can study this?

Textbook I have (X-Ray Diffraction from Warren) doesn't explain it very clearly to me and Google search didn't give the good sources.
 
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  • #2

Related to How to Determine the Unit Cell Type From the XRD Data?

1. What is X-ray Diffraction (XRD) and how is it used to determine the unit cell type?

X-ray Diffraction (XRD) is a technique used to study the crystallographic structure of materials. By directing X-rays at a crystalline sample and measuring the angles and intensities of the diffracted beams, one can obtain a diffraction pattern. This pattern contains information about the atomic arrangement within the crystal, which can be analyzed to determine the unit cell type.

2. What are the key parameters obtained from XRD data that help in identifying the unit cell type?

The key parameters obtained from XRD data include the diffraction angles (2θ), the interplanar spacings (d-spacings), and the intensities of the diffracted peaks. These parameters are used to calculate the lattice parameters (a, b, c) and angles (α, β, γ) of the unit cell, which can then be compared to known crystallographic databases to identify the unit cell type.

3. How do you index the diffraction peaks in XRD data?

Indexing the diffraction peaks involves assigning Miller indices (hkl) to each observed peak in the XRD pattern. This process typically starts with identifying the peaks corresponding to low Miller indices and using the known relationships between the lattice parameters and the d-spacings for different crystal systems. Software tools and databases can assist in this process by matching the observed peaks to known patterns.

4. What is the role of symmetry in determining the unit cell type from XRD data?

Symmetry plays a crucial role in determining the unit cell type. Different crystal systems (cubic, tetragonal, orthorhombic, etc.) have distinct symmetry properties that affect the arrangement and intensity of diffraction peaks. By analyzing the symmetry of the observed diffraction pattern, one can narrow down the possible crystal systems and identify the unit cell type.

5. Can software tools be used to determine the unit cell type from XRD data, and how reliable are they?

Yes, software tools can be used to analyze XRD data and determine the unit cell type. These tools use algorithms to match the observed diffraction pattern with known patterns in crystallographic databases. While these tools are generally reliable and can significantly speed up the analysis process, it is important to verify the results with additional data and expert judgment to ensure accuracy.

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