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Title: Liquid–liquid phase transition in hydrogen by coupled electron–ion Monte Carlo simulations

The phase diagram of high-pressure hydrogen is of great interest for fundamental research, planetary physics, and energy applications. A first-order phase transition in the fluid phase between a molecular insulating fluid and a monoatomic metallic fluid has been predicted. The existence and precise location of the transition line is relevant for planetary models. Recent experiments reported contrasting results about the location of the transition. Theoretical results based on density functional theory are also very scattered. We report highly accurate coupled electron-ion Monte Carlo calculations of this transition, finding results that lie between the two experimental predictions, close to that measured in diamond anvil cell experiments but at 25-30 GPa higher pressure. Here, the transition along an isotherm is signaled by a discontinuity in the specific volume, a sudden dissociation of the molecules, a jump in electrical conductivity, and loss of electron localization.
Authors:
ORCiD logo [1] ;  [2] ;  [3] ;  [4] ;  [5]
  1. Univ. of L'Aquila, L'Aquila (Italy)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. Sapienza Univ. of Rome, Rome (Italy)
  4. CNRS and Univ. Grenoble Alpes, Grenoble (France)
  5. Univ. of Illinois Urbana-Champaign, Champaign, IL (United States)
Publication Date:
Grant/Contract Number:
NA0002911; AC52-07NA27344; NA0001789
Type:
Published Article
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 113; Journal Issue: 18; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Univ. of Illinois Urbana-Champaign, Champaign, IL (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 97 MATHEMATICS AND COMPUTING; high pressure; phase transitions; quantum Monte Carlo; hydrogen metallization; molecular dissociation
OSTI Identifier:
1248409
Alternate Identifier(s):
OSTI ID: 1335030; OSTI ID: 1358614