Crystallography365

Blogging a crystal structure a day in 2014

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Andrew Studer

ThCr2Si2: giving it the old 1-2-2

What does it look like?

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

Image generated by the VESTA (Visualisation for Electronic and STructural analysis) software http://jp-minerals.org/vesta/en/

What is it?

Thorium chromium silicide is the prototypical structure for a whole range of materials of the form RT2X2. The structure is tetragonal. R is a Group 1, Group 2 or rare earth element, shown here in green. T is a transition metal (coloured red). X is a group 14 or 15 element (shown in blue).

That gives a lot of combinations.

What's more, there's nothing that says each component has to be a single element. For example, the X is commonly Si or Ge, but it could be any mix of the two.

Ternary compounds such as this provide huge scope for exploration. For example, R and T can both have magnetic moments which interact strongly with each other, so the magnetic properties of this class of materials can be highly intricate.

Where does the structure come from?

This structure was first published as: Ban, Z.; and Sikirica, M. Acta Crystallographica 18 (1965) p594-p599

Reference: Andrej Szytula and Janusz Leciejewicz: CRC Handbook of Crystal Structures and Magnetic Properties of Rare Earth Intermetallics

Tags: physics   inorganic   rare earth