title: Dense Hydrocarbon Structures at Megabar Pressures.
abstract: The structure, bonding, and other properties of phases in the carbon-hydrogen system over a range of conditions are of considerable importance to a broad range of scientific problems. However, the phase diagram of the C-H system at high pressures and temperatures is still not known. To search for new low-energy hydrocarbon structures, we carried out systematic structure prediction calculations for the C-H system from 100 to 300 GPa. We confirmed several previously predicted structures but found additional compositions that adopt more stable structures. In particular, a C2H4structure is found that has an indirect band gap, and phonon calculations confirm that it is dynamically stable over a broad pressure range. We also identify more carbon-rich structures that are energetically favorable. The results are important for understanding carbon-hydrogen interactions in high-pressure experiments, dense astrophysical environments and the deep carbon cycle in planetary interiors.
authors.affiliation: Geophysical Laboratory, Carnegie Institution of Washington , Washington, D.C. 20015, United States.
authors.forename: Hanyu
authors.initials: H
authors.lastname: Liu
authors.affiliation: Geophysical Laboratory, Carnegie Institution of Washington , Washington, D.C. 20015, United States.
authors.forename: Ivan I
authors.initials: II
authors.lastname: Naumov
authors.affiliation: Department of Civil and Environmental Engineering, The George Washington University , Washington, D.C. 20052 United States.|Lawrence Livermore National Laboratory , Livermore, California 94550 United States.
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Hemley