Bonding nature and structural phase transition in fullerene based nanomaterials

Area of Science:

• Materials Science
• Solid State Chemistry
• Nanotechnology

Background:

• Fullerides, particularly those doped with rare-earth metals like R3C70 (R = Sm, Eu, Yb), exhibit complex pseudomonoclinic structures.
• These structures involve C70 dimers interconnected by rare-earth ions, influencing their physical properties.

Purpose of the Study:

• To investigate the high-temperature structural behavior of rare-earth-metal-doped fullerides (R3C70).
• To understand the nature of structural phase transitions in these materials and their relationship to bonding.

Main Methods:

• High-temperature powder X-ray diffraction was employed to study structural changes.
• Detailed structural analyses and charge density mapping were performed.

Main Results:

• Reversible first-order structural phase transitions were observed in R3C70 fullerides upon heating.
• These transitions involve the dissociation of C70 dimers into monomers, accompanied by a significant reduction in unit cell volume.
• C70 molecules realign into closely packed structures at high temperatures.

Conclusions:

• The observed transitions are reversible structural changes from fullerene dimers to monomers.
• These phenomena are attributed to the distinctive bonding characteristics of rare-earth C70 compounds.
• The findings provide insights into the dynamic structural behavior of fullerides under thermal stress.