Related papers: Anomalous melting behavior of solid hydrogen at hi…
We introduce an efficient scheme for the molecular dynamics of electronic systems by means of quantum Monte Carlo. The evaluation of the (Born-Oppenheimer) forces acting on the ionic positions is achieved by two main ingredients: i) the…
Hydrogen exhibits unusual behaviors at megabar pressures, with consequences for planetary science, condensed matter physics and materials science. Experiments at such extreme conditions are challenging, often resulting in hard-to-interpret…
The study of the high pressure phase diagram of hydrogen has continued with renewed effort for about one century as it remains a fundamental challenge for experimental and theoretical techniques. Here we employ an efficient molecular…
In the quest to make metallic hydrogen at low temperatures a rich number of new phases have been found and the highest pressure ones have somewhat flat phase lines, around room temperature. We have studied hydrogen to static pressures of…
We have studied dense hydrogen and deuterium experimentally up to 320 GPa and using ab initio molecular dynamic (MD) simulations up to 370 GPa between 250 and 300 K. Raman and optical absorption spectra show significant anharmonic and…
Understanding the behavior of molecular systems under pressure is a fundamental problem in condensed matter physics. In the case of nitrogen, the determination of the phase diagram and in particular of the melting line, are largely open…
We perform molecular dynamics simulations driven by accurate Quantum Monte Carlo forces on dense liquid hydrogen. Recently it has been reported a complete atomization transition between a mixed-atomic liquid and a completely dissociated…
In recent years there has been intense experimental activity to observe solid metallic hydrogen. Wigner and Huntington predicted that under extreme pressures insulating molecular hydrogen would dissociate and transition to atomic metallic…
A torsional oscillator study of solid para-hydrogen has been carried out down to 20 mK in search for evidence of superfluidity. This work was inspired by the observation of the supersolid phase in solid He-4. We found evidence of a possible…
The properties of liquid helium have always been a fascinating subject to scientists. The phonon theory of liquids taking into account liquid non-static shear rigidity is employed here for studying internal energy and heat capacity of…
The pressure-temperature phase diagram of a one-component system, with particles interacting through a spherically symmetric pair potential in two dimensions is studied. The interaction consists of a hard core plus an additional repulsion…
The electrical resistivity of liquid hydrogen has been measured at the high dynamic pressures, densities and temperatures that can be achieved with a reverberating shock wave. The resulting data are most naturally interpreted in terms of a…
We describe experiments where 2D atomic hydrogen gas is compressed thermally at a small "cold spot" on the surface of superfluid helium and detected directly with electron-spin resonance. We reach surface densities up to 5e12 1/cm^2 at…
The equation of state of liquid metallic hydrogen is solved numerically. Investigations are carried out at temperatures, which correspond both to the experimental conditions under which metallic hydrogen is produced on earth and the…
We have studied solid hydrogen under pressure at low temperatures. With increasing pressure we observe changes in the sample, going from transparent, to black, to a reflective metal, the latter studied at a pressure of 495 GPa. We have…
Liquid-liquid phase transition of hydrogen is at the center of hydrogen phase diagram as a promising route towards emergent properties such as the Wigner-Huntington metallization, superconductivity, and superfluidity. Here we report a study…
Quantum effects in condensed matter normally only occur at low temperatures. Here we show a large quantum effect in high-pressure liquid hydrogen at thousands of Kelvins. We show that the metallization transition in hydrogen is subject to a…
Fluid polyamorphism, the existence of multiple amorphous fluid states in a single-component system, has been observed or predicted in a variety of substances. A remarkable example of this phenomenon is the fluid-fluid phase transition in…
Polyhydrides have been shown to form novel structures at high pressure, which may be found in the interiors of giant planets. With density functional molecular dynamics simulations we studied the behavior of ammonium polyhydride compounds…
The high-pressure II-III phase transition in solid hydrogen is investigated using the random phase approximation and diffusion Monte Carlo. Good agreement between the methods is found confirming that an accurate treatment of exchange and…