Reversible Pressure-Induced Amorphization in Solid C70 : Raman and Photoluminescence Study

TL;DR

This study investigates how solid C70 undergoes reversible amorphization under high pressure, showing that it returns to its original crystalline form after pressure release, unlike C60.

Contribution

It provides experimental evidence of reversible pressure-induced amorphization in C70, contrasting with the behavior of C60, and offers a qualitative explanation based on molecular interactions.

Findings

C70 remains stable up to 31.1 GPa

Amorphous phase is reversible upon pressure release

Contrasts with irreversible behavior in C60

Abstract

We have studied single crystals of $C_{70}$ by Raman scattering and photoluminescence in the pressure range from 0 to 31.1 GPa. The Raman spectrum at 31.1 GPa shows only a broad band similar to that of the amorphous carbon without any trace of the Raman lines of $C_{70}$. After releasing the pressure from 31.1 GPa, the Raman and the photoluminescence spectra of the recovered sample are that of the starting $C_{70}$ crystal. These results indicate that the $C_{70}$ molecules are stable upto 31.1 GPa and the amorphous carbon high pressure phase is reversible, in sharp contrast to the results on solid $C_{60}$. A qualitative explaination is suggested in terms of inter- versus intra-molecular interactions.