Molecular dynamics studies of CaAl2Si2O8 liquid. Part II: Equation of state and a thermodynamic model

Structure, thermodynamics, and diffusion in CaAl2Si2O8 liquid from first-principles molecular dynamics

“…This is in contrast to the shock wave data interpretation of Asimow and Ahrens (in press), which is compounded by the behavior of shot #672, and also to the findings of Ghiorso et al (2009) (Stixrude and Karki, 2005;de Koker et al, 2008;de Koker and Stixrude, 2009), and the 5th order expansion necessary to represent pure SiO 2 liquid (Karki et al, 2007;de Koker and Stixrude, 2009), consistent with both ring statistics as well as coordination changes play a role in compression at low pressure.…”

“…Most notable is the agreement we find with the Hugoniot data at P > 80 GPa. These data are poorly modeled by the classical molecular dynamics study of Ghiorso et al (2009) where an ab initio parameterized potential set is used to represent bonding. The insufficient liquid compressibility responsible for the high-P disagreement found in that study also accounts for the larger self-diffusion activation volumes in the study of Spera et al (2009) which uses the same set of simulation results.…”

“…Previous theoretical studies used parameterized potential simulations, and revealed a number of interesting phenomena (e.g. Angell et al, 1982;Nevins and Spera, 1998;Ghiorso et al, 2009;Spera et al, 2009). However, the reliability of these results is difficult to judge, owing to the simplicity of the bonding representation used.…”

Interstitial voids in silica melts and implication for argon solubility under high pressures

“…They also reported that the concentration of V T maximizes around 5 GPa. Recently, Spera et al (2009) and Ghiorso et al (2009) infer that there is a phase transition-like behavior in the liquid CaAl 2 Si 2 O 8 in the range of 15-20 GPa. These discontinuities are not found in our simulation of liquid Fig.…”

Structure, thermodynamic and transport properties of CaAl2Si2O8 liquid. Part I: Molecular dynamics simulations

“…Construction of an EOS requires approximately 75-100 state points more or less evenly distributed over the appropriate P-T region; a few P-T points on a few compositions are woefully insufficient. In this study (Part I) and its companion (Part II, Ghiorso et al, 2009) molten CaAl 2-Si 2 O 8 is studied in detail. In Part I (this study) details on the MD simulations, retrieved thermodynamic and transport properties and melt structures are provided and compared with available laboratory information.…”