title: Nonlinear carbon dioxide at high pressures and temperatures.
abstract: A nonlinear molecular carbon dioxide phase IV was discovered by laser heating CO2-III (Cmca) between 12 and 30 GPa, followed by quenching to 300 K. The Raman spectrum of quenched CO2-IV exhibits a triplet bending mode nu2(O = C = O) near 650 cm (-1), suggesting a broken inversion symmetry because of bending. The 650 cm (-1) bending modes soften with increasing pressure, indicating an enhanced intermolecular interaction among neighboring bent CO2 molecules. At 80 GPa, the low-frequency vibron collapses into high-frequency phonons, and CO2-IV becomes an extended amorphous solid.
authors.affiliation: Lawrence Livermore National Laboratory, Livermore, California 94551, USA.
authors.forename: C S
authors.initials: CS
authors.lastname: Yoo
authors.forename: V
authors.initials: V
authors.lastname: Iota
authors.forename: H
authors.initials: H
authors.lastname: Cynn