Regensburg 2019 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 12: Poster session I

MM 12.24: Poster

Montag, 1. April 2019, 19:15–20:45, Poster C

A first-principles study of the phase diagram of solid hydrogen — •Alice Shipley, John Trail, and Richard Needs — Cavendish Laboratory, University of Cambridge, UK

Hydrogen is the most abundant element in the universe and the simplest atom. However, the behaviour of dense hydrogen is far from simple. Solid hydrogen possesses a rich phase diagram and, as a substance predicted to exhibit room-temperature superconductivity at high pressures [PRL 21, 1748 (1968)], has been of experimental and theoretical interest for decades. In computational studies, density functional theory (DFT) traditionally offers an attractive balance between accuracy and cost; a consideration which is essential here as there are many candidate structures separated by static-lattice enthalpy differences on the order of meV/atom. It is therefore also essential to consider vibrational effects in order to determine phase stability. Unfortunately, the solid hydrogen phase diagrams produced using different standard exchange-correlation functionals do not qualitatively agree with one another. With this in mind, our work explores the accuracy of purpose-built exchange-correlation functionals for high-pressure hydrogen [PRB 95, 115116 (2017)]. The new pressure-temperature phase diagrams obtained will be presented alongside a discussion of the vibrational self-consistent field (VSCF) approach [PRB 87, 144302 (2013)] used to incorporate vibrational effects, including anharmonicity.