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. 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.
Department of Physical and Chemical Sciences, University of L'Aquila, Via Vetoio 10, I-67010 L'Aquila, Italy; carlo.pierleoni@aquila.infn.it ceperley@uiuc.edu.
Carlo
0000-0001-9188-3846
C
Pierleoni
Physics Division, Lawrence Livermore National Laboratory, Livermore, CA 94550;
Miguel A
MA
Morales
Department of Physics, Sapienza University of Rome, 00185 Rome, Italy;
Giovanni
G
Rillo
Laboratoire de Physique et Modélisation des Milieux Condensés, CNRS and Université Grenoble Alpes, F-38000 Grenoble, France;
Markus
M
Holzmann
Department of Physics, University of Illinois at Urbana-Champaign, Champaign, IL 61801 carlo.pierleoni@aquila.infn.it ceperley@uiuc.edu.
David M
DM
Ceperley
high pressure; hydrogen metallization; molecular dissociation; phase transitions; quantum Monte Carlo