Mechanical properties of C 60 at finite temperature from first-principles calculations

• Published in: Diamond and related materials Vol. 123
• Main Author: Pizzagalli, Laurent
• Format: Journal Article
• Language: English
• Published: Elsevier 01.03.2022
• Subjects: Chemical Sciences; Condensed Matter; Material chemistry; Materials Science; Physics; first-principles molecular dynamics calculations; buckminsterfullerene C 60; mechanical properties
• ISSN: 0925-9635
• DOI: 10.1016/j.diamond.2022.108870

C 60 has been the focus of many studies since its discovery, but the mechanical properties of this unique molecule remain poorly known. To remedy that, we performed density functional theory molecular dynamics calculations of the compression of C 60 at finite temperature, within a large strain range. The possible recovery of the molecule after unloading was also investigated with first principles accuracy, for two different modes. We found that the behavior of C 60 follows three regimes depending on the compression strain. Up to 0.48 ± 0.02, the deformation is elastic with a small but distinct influence of the compression orientation. A relation between the electronic gap and the orientation is also revealed. The second regime starts for larger strains up to 0.75 ± 0.02, after a 30-32 nN force plateau. It is characterized by stochastic carbon bond breakings. Although bonds rupture is generally the fingerprint of plastic deformation in materials, we found that the C 60 structure can be dynamically recovered in a significant fraction of cases, following a fast unloading. This mode also yields defected structures with low energies compared to a slow unloading mode. Finally, the third regime corresponds to irreversible deformation of the molecule, for strains larger than 0.75 ± 0.02.