Phase transitions at high pressure in the fullerene C60 molecular donor-acceptor complex {Hg(dedtc)2}2 · C60

Abstract

Raman spectra of crystals of the molecular fullerene C60 donor-acceptor complex {Hg(dedtc)2}2 · C60 (fullerene with mercury diethyldithiocarbamate) have been measured at a pressure up to 8.4 GPa and at room temperature. A phase transition has been revealed in the pressure range of 1.2–2.0 GPa, which is accompanied by a splitting of the degenerate intramolecular phonon modes Hg(1)-Hg(4) and Hg(7)-Hg(8), as well as by a softening of the Hg(2) mode of the fullerene C60. As the pressure further increases to the maximum value, the intensity of the bands varies smoothly. A decrease in the pressure leads to the reverse transition to the initial state at 1.2 GPa. The splitting of the degenerate modes Hg(1)-Hg(8) and the softening of the Hg(2) modes resemble their behavior in the formation of dimers in fullerite crystals and indicate the possible formation of dimers in two-dimensional fullerene layers under hydrostatic compression of the {Hg(dedtc)2}2 · C60 complex.