Shear viscosity and diffusion in liquid MgSiO3: Transport properties and implications for terrestrial planet magma oceans
نویسندگان
چکیده
Molecular dynamics simulations using a pair-wise additive potential are implemented to investigate self-diffusion (Mg, Si, and O) and shear viscosity of liquid MgSiO3 in the density-temperaturepressure range 2350–5300 kg/m3, 2500–5000 K, and 0–140 GPa, respectively. Self-diffusivity and shear viscosity are described by modified Arrhenian expressions, which feature a pressure-dependent activation volume. Activation energies for self-diffusion (Mg, Si, and O) and viscous flow are 99.6, 109.3, 97.4, and 95.3 kJ/mol, respectively; evidently oxygen mobility dominates liquid dynamics. Activation volumes for self-diffusion and shear viscosity at low (2–5 GPa) pressure are ~1 cm3/mol with self-diffusion decreasing and shear viscosity increasing as pressure increases although there is a small interval near zero pressure within which diffusivity increases slightly with increasing pressure. Shear viscosity increases by a factor of 75 along the 3000 K isotherm from the top of the mantle to the core-mantle boundary. Along the 3000 K isentrope relevant to terrestrial magma ocean convection, shear viscosity increases by about a factor of three. The equivalence conditions between the StokesEinstein and Eyring transport models are derived. The Eyring model provides information on the size of the activated complex associated with viscous flow across the range in pressures relevant to the Earth’s mantle and suggests that the number of atoms in the activated complex associated with shear flow decreases from ~8 atoms at low pressure to ~4 atoms at high pressure at 4500 K.
منابع مشابه
Shear viscosity and diffusion in liquid MgSiO 3 : Transport properties and implications for 2 terrestrial planet magma oceans 3
متن کامل
Structure, thermodynamic and transport properties of liquid MgSiO3: Comparison of molecular models and laboratory results
Liquid MgSiO3 is a model for the Earth’s magma ocean and of remnant melt present near the core–mantle boundary. Here, models for molten MgSiO3 are computed employing empirical potential molecular dynamics (EPMD) and results are compared to published results including two EPMD studies and three first-principles molecular dynamics (FPMD) models and to laboratory data. The EPMD results derived fro...
متن کاملPrediction of transport properties by molecular simulation: methanol and ethanol and their mixture.
Transport properties of liquid methanol and ethanol are predicted by molecular dynamics simulation. The molecular models for the alcohols are rigid, nonpolarizable, and of united-atom type. They were developed in preceding work using experimental vapor-liquid equilibrium data only. Self- and Maxwell-Stefan diffusion coefficients as well as the shear viscosity of methanol, ethanol, and their bin...
متن کاملSemi Empirical Calculation of Intermolecular Potentials and Transport Properties of Some Binary and Ternary Industrial Refrigerant Mixtures
In this study the intermolecular potential energies of some environment-friendly industrial HFC refrigerants were obtained through the inversion method which is based on the corresponding states principle. These potentials were later employed in calculation of transport properties (viscosity, diffusion, thermal conductivity and thermal diffusion factor) of some binary and ternary refrigerant mi...
متن کاملSome recent advances in understanding the mineralogy of Earth's deep mantle.
Understanding planetary structure and evolution requires a detailed knowledge of the properties of geological materials under the conditions of deep planetary interiors. Experiments under the extreme pressure-temperature conditions of the deep mantle are challenging, and many fundamental properties remain poorly constrained or are inferred only through uncertain extrapolations from lower pressu...
متن کامل