Molecular to atomic phase transition in hydrogen under high pressure
Jeremy McMinis1, Raymond C Clay1,2, Donghwa Lee1
1Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
Physical Review Letters
|March 28, 2015
Summary
Quantum Monte Carlo calculations reveal the molecular to atomic transition in hydrogen occurs at 447(3) GPa. This finding aligns with experimental data and clarifies the stability of hydrogen phases under extreme pressure.
Area of Science:
- High-pressure physics
- Condensed matter physics
- Quantum many-body physics
Background:
- The metallization of hydrogen under extreme pressure is a pivotal, debated topic in high-pressure physics.
- Conflicting experimental results from diamond-anvil cells challenge current understanding.
- Density functional theory (DFT), commonly used for theoretical calculations, has limitations in describing metal-insulator transitions and is sensitive to exchange-correlation functionals.
Purpose of the Study:
- To investigate the molecular to atomic transition in hydrogen using advanced quantum simulation methods.
- To resolve discrepancies in experimental observations and theoretical predictions regarding hydrogen's metallic state.
- To determine the precise transition pressure and phase stability of hydrogen under extreme conditions.
Main Methods:
- Utilized quantum Monte Carlo (QMC) calculations, a robust method for simulating quantum many-body systems.
- Studied the electronic correlation and phase transitions in hydrogen at pressures up to several hundred gigapascals.
- Calculated the transition pressure and analyzed the stability of different hydrogen crystal structures.
Main Results:
- Determined a transition pressure of 447(3) GPa for the molecular to atomic transition in hydrogen.
- Achieved excellent agreement with the experimental estimate of 450 GPa, derived from band gap extrapolation.
- Found the C2/c phase of hydrogen to be stable up to the transition pressure, contradicting some prior DFT predictions.
Conclusions:
- QMC calculations provide a reliable pathway for understanding hydrogen's behavior under extreme pressure.
- The study resolves long-standing debates by providing accurate transition pressure and phase stability data.
- Results challenge previous theoretical models that predicted extended stability for intermediate molecular phases.
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