Structure and metallicity of phase V of hydrogen

Abstract

A new phase V of hydrogen was recently claimed in experiments above 325 GPa and 300 K. Due to the extremely small sample size at such record pressures the measurements were limited to Raman spectroscopy. The experimental data on increase of pressure shows decreasing Raman activity and darkening of the sample, which suggests band-gap closure and impending molecular dissociation, but no definite conclusions could be reached. Furthermore, the available data is insufficient to determine the structure of phase V, which remains unknown. Introducing saddle-point $ab$ $initio$ random structure searching (sp-AIRSS), we find several new structural candidates of hydrogen which could describe the observed properties of phase V. We investigate hydrogen metallisation in the proposed candidate structures, and demonstrate that smaller band gaps are associated with longer bond lengths. We conclude that phase V is a stepping stone towards metallisation.

arXiv comment7 pages, 3 figures, includes Supplemental Material

References in corpus (26)

• Crystal Structure Prediction via Particle Swarm Optimization
• Ab initio Random Structure Searching
• High-pressure phases of silane
• Lattice dynamics of anharmonic solids from first principles
• Phase transitions in BaTiO${}_3$ from first principles
• Observation of the Wigner-Huntington Transition to Solid Metallic Hydrogen
• Anharmonic free energies and phonon dispersions from the stochastic self-consistent harmonic approximation: application to platinum and palladium hydrides
• Entropy driven stabilization of energetically unstable crystal structures explained from first principles theory
• Continuum variational and diffusion quantum Monte Carlo calculations
• Twist-averaged Boundary Conditions in Continuum Quantum Monte Carlo
• High-Temperature Superconductivity in Atomic Metallic Hydrogen
• Anharmonic vibrational properties in periodic systems: energy, electron-phonon coupling, and stress
• Density functional theory study of phase IV of solid hydrogen
• Lattice dynamics and electron-phonon coupling calculations using non-diagonal supercells
• Dissociation of high-pressure solid molecular hydrogen: Quantum Monte Carlo and anharmonic vibrational study
• Finite-size correction in many-body electronic structure calculations
• Quantum Monte Carlo study of the phase diagram of solid molecular hydrogen at extreme pressures
• Benchmark of Exchange-Correlation Functionals for High Pressure Hydrogen using Quantum Monte Carlo
• Towards a Predictive First-Principles Description of Solid Molecular Hydrogen with Density-Functional Theory
• Comment on "Observation of the Wigner-Huntington transition to metallic hydrogen"
• Fate of density functional theory in high-pressure solid hydrogen
• Room-Temperature Structures of Solid Hydrogen at High Pressures
• Hexagonal structure of phase III of solid hydrogen
• Nature of the Metallization Transition in Solid Hydrogen
• Quantum Monte Carlo Study of High Pressure Solid Molecular Hydrogen
• Fast Free Energy Calculations for Unstable High-Temperature Phases

Cited by in corpus (31)

• A Perspective on Conventional High-Temperature Superconductors at High Pressure: Methods and Materials
• High-Temperature Superconductivity in Cerium Superhydrides
• Superconducting hydrides under pressure
• Towards high-throughput superconductor discovery via machine learning
• The Stochastic Self-Consistent Harmonic Approximation: Calculating Vibrational Properties of Materials with Full Quantum and Anharmonic Effects
• Variational and Diffusion Quantum Monte Carlo Calculations with the CASINO Code
• High-throughput discovery of high-temperature conventional superconductors
• Using Gaussian Process Regression to Simulate the Vibrational Raman Spectra of Molecular Crystals
• First principles simulations of dense hydrogen
• High Tc superconductivity in heavy Rare Earth Hydrides: correlation between the presence of the f states on the Fermi surface, nesting and the value of Tc
• Quantum phase diagram of high-pressure hydrogen
• Energy gap closure of crystalline molecular hydrogen with pressure
• Al-Based Few-Hydrogen Metal-Bonded Perovskite High-$T_c$ Superconductor Al${}_4$H up to 54 K under Atmospheric Pressure
• Predicting the phase diagram of titanium dioxide with random search and pattern recognition
• Emergence of topological electronic phases in elemental lithium under pressure
• Unconventional phase III of high-pressure solid hydrogen
• Observed Metallization of Hydrogen Interpreted as a Band Structure Effect
• Nuclear magnetic resonance spectroscopy as a dynamical structural probe of high pressure hydrogen
• High Temperature Superconductivity in the Candidate Phases of Solid Hydrogen
• Candidate structure for the H${}_2$-PRE phase of solid hydrogen
• Prediction of High Temperature Superconductivity in C2/c-24 Solid Hydrogen
• First-principles anharmonic vibrational study of the structure of calcium silicate perovskite under lower mantle conditions
• Reproducibility of fixed-node diffusion Monte Carlo across diverse community codes: The case of water-methane dimer
• Semimetallic molecular hydrogen at pressure above 350 GPa
• Temperature-driven narrowing of the insulating gap as a precursor of the insulator-to-metal transition: Implications for the electronic structure of solids
• Crystal structures and high-temperature superconductivity in molybdenum-hydrogen binary system under high pressure
• Anisotropy and Isotope Effect in Superconducting Solid Hydrogen
• GW space-time method: Energy band-gap of solid hydrogen
• Organic compounds in metallic hydrogen
• Geometry-Based Neural-Network Prediction of Electron Localization Function Topology in Dense Hydrogen
• Superatomic hydrogen: achieving effective aggregation of hydrogen atoms at pressures lower than that of metallic hydrogen