Polymerization of Benzene at Extreme P-T Conditions

While the compression of benzene, the archetypal aromatic, to about 20 GPa is assessed to lead to the synthesis of partially crystalline, hydrogenated sp3 carbon nano-threads, the fate of benzene at more extreme conditions was poorly experimentally known. Our beam-time CH-6478 was devoted to push this frontier further. We heated benzene in DACs at pressures of 40-75 GPa by direct CO2 laser heating, thus avoiding potentially reactive absorbers. We found the laser-sample coupling to be critically dependent on the type of the diamonds, i.e IIas vs. Ia and, for one sample, we obtained temperatures of almost 2000 K with 60% of the maximum laser power. In this case, the T quenched material exhibited a small (about 5 micron) single crystal (SC) product, which we investigated via SC XRD and identified as a hexagonal phase, likely graphane, the DFT predicted thermodynamic extended phase for 1:1 CH stoichiometry. We now need to reproduce this result under improved experimental conditions.