Related papers: Ab initio Simulations of Superionic H2O, H2O2, and…
Water is abundant in natural environments but the form it resides in planetary interiors remains uncertain. We report combined synchrotron X-ray diffraction and optical spectroscopy measurements of H2O in the laser-heated diamond anvil cell…
Water and hydrogen at high pressure make up a substantial fraction of the interiors of giant planets. Using ab initio random structure search methods we investigate the ground-state crystal structures of water, hydrogen, and hydrogen-oxygen…
Most water in the universe may be superionic, and its thermodynamic and transport properties are crucial for planetary science but difficult to probe experimentally or theoretically. We use machine learning and free energy methods to…
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…
A large number of water models exists for molecular simulations. They differ in the ability to reproduce specific features of real water instead of others, like the correct temperature for the density maximum or the diffusion coefficient.…
High pressure behaviour of liquid GeO2 is investigated by means of molecular dynamics simulations in the pressure range 0-20 GPa and at various temperatures. In agreement with the recent experiments (PRL, 92, 155506, 2004), Ge-O…
Gas hydrates are systems of prime importance. In particular, hydrogen hydrates are potential materials of icy satellites and comets, and may be used for hydrogen storage. We explore the H2O-H2 system at pressures in the range 0-100 GPa with…
Silica, water and hydrogen are known to be the major components of celestial bodies, and have significant influence on the formation and evolution of giant planets, such as Uranus and Neptune. Thus, it is of fundamental importance to…
Using density functional molecular dynamics free energy calculations, we show that the body-centered-cubic phase of superionic ice previously believed to be the only phase is in fact thermodynamically unstable compared to a novel phase with…
Knowing the phase transformations in dense water ice is key to unraveling the peculiar geophysical properties of Uranus and Neptune, whose stratified interior models predict a thick ice layer beneath a convective ionic fluid layer. In the…
Water shows anomalous properties that are enhanced upon supercooling. The unusual behavior is observed in both H$_2$O and D$_2$O, however with different temperature dependences for the two isotopes. It is often noted that comparing the…
Hydrogen-sulfide (H2S) was studied by x-ray synchrotron diffraction (XRD) and Raman spectroscopy up to 150 GPa at 180-295 K and by quantum-mechanical variable-composition evolutionary simulations. The experiments show that H2S becomes…
The superionic state is a phase of matter in which liquid-like ionic mobility coexists with a solid crystalline lattice. Recently identified in Earth's inner core (IC), this state has attracted considerable attention for its unique kinetic…
\textit{Ab initio} random structure searching based on density functional theory is used to determine the ground-state structures of ice at high pressures. Including estimates of lattice zero-point energies, ice is found to adopt three…
We propose three new phases of H2O under ultrahigh pressure. Our structural search was performed using an adaptive genetic algorithm which allows an extensive exploration of crystal structure. The new sequence of pressure-induced…
Density Functional Theory calculations using the quasi-harmonic approximation have been used to calculate the solid Hugoniot of two polytypes of boron carbide up to 100 GPa. Under the assumption that segregation into the elemental phases…
Computational searches for stable and metastable structures of water ice and other H:O compositions at TPa pressures have led us to predict that H$_2$O decomposes into H$_2$O$_2$ and a hydrogen-rich phase at pressures of a little over 5…
Hydrogen sulfide (H2S) is a prototype molecular system and a sister molecule of water. The phase diagram of solid H2S at high pressures remains largely unexplored arising from the challenges in dealing with the looser S-H bond and larger…
Superionic ice, where water molecules dissociate into a lattice of oxygen ions and a rapidly diffusing 'gas' of protons, represents an exotic state of matter with broad implications for planetary interiors and energy applications. Recently,…
We use molecular simulation to compute the thermodynamic properties of 7 rigid models for water (SPC/E, TIP3P, TIP4P, TIP4P/2005, TIP4P/Ew, TIP5P, OPC) over a wide range of temperature and pressure. Carrying out Expanded Wang-Landau…