Related Experiment Video
Updated: May 22, 2026
14:11
Quantification of Hydrogen Concentrations in Surface and Interface Layers and Bulk Materials through Depth Profiling with Nuclear Reaction Analysis
Published on: March 29, 2016
Mixed molecular and atomic phase of dense hydrogen
Ross T Howie1, Christophe L Guillaume, Thomas Scheler
1Centre for Science at Extreme Conditions and School of Physic and Astronomy, University of Edinburgh, Edinburgh, EH9 3JZ, United Kingdom.
Physical Review Letters
|May 1, 2012
Summary
Researchers studied dense hydrogen (deuterium) under extreme pressure, revealing a new phase (IV) at 220 GPa. This phase exhibits unique vibrational properties and a closing band gap, suggesting a mix of bonded and unbound molecules.
Area of Science:
- Condensed matter physics
- High-pressure physics
- Materials science
Background:
- Hydrogen exhibits complex phase behavior under extreme pressures.
- Previous studies on hydrogen phases were limited to low temperatures.
Purpose of the Study:
- To investigate the phase transitions of dense hydrogen (deuterium) at high pressures and 300 K.
- To characterize the properties of newly observed high-pressure phases.
Main Methods:
- Raman spectroscopy
- Visible transmission spectroscopy
- High-pressure diamond anvil cells
Main Results:
- Observed phase transformation to phase III around 200 GPa.
- Identified a new reversible phase (IV) at 220 GPa.
- Phase IV shows increased absorption, a band gap of 1.8 eV at 315 GPa, new phonon excitations, and softened vibrational modes.
Conclusions:
- Phase IV is a novel state of dense hydrogen.
- Phase IV likely consists of graphenelike layers of H2 dimers and unbound H2 molecules.
- The observed properties suggest significant pairing fluctuations in H2 dimers.
Related Concept Videos
01:04Hydrogen Bonds
A hydrogen bond is formed when a weakly positive hydrogen atom already bonded to one electronegative atom (for example, the oxygen in the water molecule) is attracted to another electronegative atom from another polar molecule, such as water (H2O), hydrogen fluoride (HF), or ammonia (NH3). The huge electronegativity difference between the H atom (2.1) and the atom to which it is bonded (4.0 for an F atom, 3.5 for an O atom, or 3.0 for an N atom), combined with the very small size of an H atom...
00:26Hydrogen Bonds
Hydrogen bonds are weak attractions between atoms that have formed other chemical bonds. One of these atoms is electronegative, like oxygen, and has a partial negative charge. The other is a hydrogen atom that has bonded with another electronegative atom and has a partial positive charge.
Hydrogen Bonds Control the World!
Because hydrogen has very weak electronegativity when it binds with a strongly electronegative atom, such as oxygen or nitrogen, electrons in the bond are unequally shared.
Hydrogen Bonds Control the World!
Because hydrogen has very weak electronegativity when it binds with a strongly electronegative atom, such as oxygen or nitrogen, electrons in the bond are unequally shared.
02:26Molecular Comparison of Gases, Liquids, and Solids
Particles in a solid are tightly packed together (fixed shape) and often arranged in a regular pattern; in a liquid, they are close together with no regular arrangement (no fixed shape); in a gas, they are far apart with no regular arrangement (no fixed shape). Particles in a solid vibrate about fixed positions (cannot flow) and do not generally move in relation to one another; in a liquid, they move past each other (can flow) but remain in essentially constant contact; in a gas, they move...
03:51Molecular Orbital Theory II
Molecular Orbital Energy Diagrams
00:59States of Matter and Phase Changes
The internal energy of a substance—the total kinetic energy of all its molecules and the potential energy of their associated forces—depends on the strength of the intermolecular forces in the condensed phases and the pressure exerted on the substance. The internal energy of a substance is the highest in the gaseous state, the lowest in the solid state, and intermediate in the liquid state. Phase transitions are caused by changes in physical conditions, such as temperature and pressure, that...
02:31Phase Transitions
Whether solid, liquid, or gas, a substance's state depends on the order and arrangement of its particles (atoms, molecules, or ions). Particles in the solid pack closely together, generally in a pattern. The particles vibrate about their fixed positions but do not move or squeeze past their neighbors. In liquids, although the particles are closely spaced, they are randomly arranged. The position of the particles are not fixed—that is, they are free to move past their neighbors to occupy...