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Dipole-quadrupole interactions and the nature of phase III of compressed hydrogen

Jorge Kohanoff·Sandro Scandolo·Stefano de Gironcoli·Erio Tosatti
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Abstract

A new class of strongly infrared active structures is identified for phase III of compressed molecular H2 by constant-pressure ab initio molecular dynamics and density-functional perturbation calculations. These are planar quadrupolar structures obtained as a distortion of low-pressure quadrupolar phases, after they become unstable at about 150 GPa due to a zone-boundary soft phonon. The nature of the II-III transition and the origin of the IR activity are rationalized by means of simple electrostatics, as the onset of a stabilizing dipole-quadrupole interaction.

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Jorge Kohanoff, Sandro Scandolo, Stefano de Gironcoli, Erio Tosatti. 1999-09-27. Dipole-quadrupole interactions and the nature of phase III of compressed hydrogen. https://doi.org/10.1103/physrevlett.83.4097

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