Structural and optical properties of liquid CO2 for pressures up to 1 TPa

Abstract

We report on the use of first-principles molecular dynamics calculations to examine properties of liquid carbon dioxide in the pressure-temperature range of 0-1 TPa and 200-100 000 K. The computed equations of state points are used to predict a series of shock Hugoniots with initial starting conditions that are relevant to existing and ongoing shock-wave experiments. A comparison with published measurements up to 70 GPa shows excellent agreement. We find that the liquid undergoes a gradual phase transition along the Hugoniot and have characterized this transition based on changes in bonding and structural properties as well as the conductivity and reflectivity of the fluid.

Ab initio simulations of liquid carbon monoxide at high pressure

“…The trajectory for each of these simulations was used to determine the atomic coordination of C atoms. Here we use the terminology employed in previous studies [23,24] to define the carbon coordination as the number of oxygen and carbon atoms within a specified radial cut-off distance of a given carbon atom. The cut-off distance used for coordination determination was the first minimum of the C O pair correlation function, see for example Boates et al [23].…”

“…All simulations were performed with periodic boundary conditions and temperatures were kept constant by a Nosé-Hoover thermostat [21,22] are converged with 32 molecules (96 atoms) in the simulation cell [23,24]. Hence we used a 3 × 3 × 3 body centered cubic supercell of 54 CO molecules (108 atoms) to mitigate finite size effects.…”

Stability and properties of liquid CO2 at high pressure and high temperature: Implications for electrical conductivities in Earth's lower mantle

“…In the theoretical study of Boates et al [2011], solid CO 2 was found to transform from an insulator to a metallic phase at the liquid-liquid transition at 42.2 GPa and 4000 K. It was suggested that metallization is related to the dissociation of CO 2 molecules and the formation of C-C bonds. This hypothesis arose from the observation that there is an apparent correlation between increasing DC conductivity and the number of the C-C species.…”

“…These extreme conditions are significant obstacles that challenge both experimental and theoretical investigations. From first-principles molecular dynamics (MD) calculations, Boates et al [2011] found a liquid-liquid phase transition at 42.2 GPa and 4000 K with the dissociation of carbon dioxide molecules into a variety of molecular species including polymer structures C-C, C-O, and molecular O 2 . A potentially important prediction from that study is that the conductivity of the dissociated liquid is similar to a metal.…”

“…Thus, the study of materials as a function of pressure and temperature almost always lead to the formation of new materials. Carbon dioxide (CO 2 ), one of the most important planetary materials, has been extensively studied in many perspectives not only related to Earth and planetary sciences but also in climate change and materials research [Kelemen and Matter, 2008;Lal, 2009;Litasov et al, 2011;Boates et al, 2011Boates et al, , 2012Yoo et al, 2011;Yoo, 2013;Teweldebrhan et al, 2013;Ague and Nicolescu, 2014]. CO 2 is a molecular gas at ambient conditions.…”