ИСТИНА

A new hydrocarbon with the composition close to CH is shown to form from graphite and gaseous hydrogen at pressures above 2 GPa and temperatures fr om 450 to 700°C. The synthesized hydrocarbon is a black solid thermally stable under ambient conditions. If heated in vacuum, it decomposes into graphite and molecular hydrogen at temperatures from 500 to 650°C. Powder X-ray [1] and neutron diffraction studies characterize the hydrogenated graphite as the bulk “graphane II” phase predicted by ab initio calculations [2]. Its crystal structure belongs to the P63mc space group and consists of graphane sheets in the chair conformation stacked along the hexagonal c -axis in the − ABAB − sequence. The a and c unit cell parameters exceed those for graphite by 2.4% and 42%, respectively. The inelastic neutron scattering spectrum of the hydrogenated graphite agrees well with the ab initio calculations [3,4] for isolated graphane sheets in the chair conformation. This confirms the predicted weak interaction among the graphane sheets in the graphane II phase [2] and makes the obtained bulk material a model object for evaluating the properties of 2D graphane layers. 1.V.E. Antonov et al., Carbon 100(2016) 465. 2. X.-D. Wen et al., PNAS 108 (2011) 6833. 3.E. Cadelano et al., Phys. Rev. B 82(2010) 235414. 4.G. Savini et al., Phys. Rev. Lett.105 (2010) 037002.