The fate of carbon dioxide in water-rich fluids at extreme conditions

Measuring the thermal conductivity ($\kappa$) of water at extreme conditions is a challenging task and few experimental data are available. We predict $\kappa$ for temperatures and pressures relevant to the conditions of the Earth mantle, between 1,000 and 2,000 K and up to 22 GPa. We employ close to equilibrium molecular dynamics simulations and a deep neural network potential fitted to density functional theory data. We then interpret our results by computing the equation o...

Quantum molecular dynamic simulations are introduced to study the dynamical, electrical, and optical properties of carbon dioxide under dynamic compressions. The principal Hugoniot derived from the calculated equation of states is demonstrated to be well accordant with experimental results. Molecular dissociation and recombination are investigated through pair correlation functions, and decomposition of carbon dioxide is found to be between 40 and 50 GPa along the Hugoniot, w...

Molecular dynamics simulations using classical force fields were carried out to study energetic and structural properties of rotationally disordered clay mineral-water-CO2 systems at pressure and temperature relevant to geological carbon storage. The simulations show that turbostratic stacking of hydrated Na- and Ca-montmorillonite and hydrated montmorillonite with intercalated carbon dioxide is an energetically demanding process accompanied by an increase in the interlayer s...

CO2 has attracted considerable attention in the recent years due to its role in the greenhouse effect and environmental management. While its reaction with water has been studied extensively, the same cannot be said for reactivity in supercritical CO2 phase, where the conjugate acid/base equilibria proceed through different mechanisms and activation barriers. In spite of the apparent simplicity of the CO2 + H2O reaction, the collective effect of different environments has dra...

We present a first principles molecular dynamics (FPMD) study of the interaction of low energy, positively charged, carbon (C+) projectiles with amorphous solid water clusters at 30 K. Reactions involving the carbon ion at an initial energy of 11 eV and 1.7 eV with 30-molecule clusters have been investigated. Simulations indicate that the neutral isoformyl radical, COH, and carbon monoxide, CO, are the dominant products of these reactions. All these reactions are accompanied ...

In the course of our investigations of the adsorption of ions to the air-water interface, we previously reported the surprising result that doubly-charged carbonate anions exhibit a stronger surface affinity than do singly-charged bicarbonate anions. In contrast to monovalent, weakly hydrated anions, which generally show enhanced concentrations in the interfacial region, multivalent (and strongly hydrated) anions are expected to show much weaker surface propensity. In the pre...

Water is an important component of exoplanets, with its distribution, i.e., whether at the surface or deep inside, fundamentally influencing the planetary properties. The distribution of water in most exoplanets is determined by yet-unknown partitioning coefficients at extreme conditions. Our new first-principles molecular dynamics simulations reveal that water strongly partitions into iron over silicate at high pressures and thus would preferentially stay in a planet's core....

Using quantum molecular dynamic simulations, we have studied the thermophysical properties of warm dense carbon monoxide under extreme conditions. The principal Hugoniot, which is derived from the equation of state, shows excellent agreement with available experimental data up to 67 GPa. The chemical decomposition of carbon monoxide has been predicted at 8 GPa by means of pair correlation function. Based on Kubo-Greenwood formula, the dc electrical conductivity and the optica...

Pools of carbon dioxide are found in natural geological accumulations and in engineered storage in saline aquifers. It has been thought that once this CO2 dissolves in the formation water, making it denser, convection streams will transport it efficiently to depth, but this may not be so. Here, we assess theoretically and experimentally the impact of natural chemical reactions between the dissolved CO2 and the rock formation on the convection streams in the subsurface. We sho...

Carbon, the fourth most abundant element in the Universe forms a metallic fluid with transient covalent bonds on melting. Its liquid-liquid phase transitions, intensely sought using simulations had been elusive. Here we use density functional theory (DFT) simulations with up to 108 atoms using molecular dynamics, as well as one-atom DFT as implemented in the neutral pseudo-atom method where multi-atom effects are treated by ion-ion correlation functionals. Both methods use el...