A5055320146- High-pressure geophysics and materials
- Geological and Geochemical Analysis
- earthquake and tectonic studies
- Crystal Structures and Properties
- Astro and Planetary Science
- Geomagnetism and Paleomagnetism Studies
- Glass properties and applications
- Zeolite Catalysis and Synthesis
- Seismic Imaging and Inversion Techniques
- Methane Hydrates and Related Phenomena
- Material Dynamics and Properties
- Planetary Science and Exploration
- Advanced Condensed Matter Physics
- Hydrocarbon exploration and reservoir analysis
- Boron and Carbon Nanomaterials Research
- Advanced ceramic materials synthesis
- Phase Equilibria and Thermodynamics
- Clay minerals and soil interactions
- Metallurgical Processes and Thermodynamics
- Iron oxide chemistry and applications
- Geochemistry and Geologic Mapping
- Earthquake Detection and Analysis
- Seismic Waves and Analysis
- Geology and Paleoclimatology Research
- X-ray Diffraction in Crystallography
Planetary Science Institute
2005-2025
University of California, Los Angeles
2019-2025
University College London
2012-2022
University of Houston
2022
UCL Australia
2018
Institute of Seismology
2017
University of California, Berkeley
1988-2011
Carnegie Institution for Science
1992-2011
Geophysical Laboratory
1992-2011
University of Milano-Bicocca
2011
We complete the development and description of a thermodynamic method for computation phase equilibria physical properties multiphase mantle assemblages. Our previous paper focused on properties. In this paper, our focus shifts to equilibria. further develop theory specify ideal excess contributions solution derive discuss global inversion strategy determining values free parameters in compare inverted parameter with expectations based scaling arguments. Comparisons between experimental data...
We present a theory for the computation of phase equilibria and physical properties multicomponent assemblages relevant to mantle Earth. The differs from previous treatments in being thermodynamically self-consistent: is based on concept fundamental thermodynamic relations appropriately generalized anisotropic strain encompassing elasticity addition usual isotropic properties. In this first paper, we development theory, discuss its scope, focus application phases at elevated pressure...
The structural and elastic properties of MgO periclase were studied up to 150 GPa with the first-principles pseudopotential method within local density approximation. calculated lattice constant B1 phase over pressure range is 1% experimental values. observed was found be stable 450 GPa, precluding B1-B2 transition lower mantle. less than one-half previous prediction but very close linearized augmented plane-wave result. All three independent constants, c(11), c(12), c(44) for are from...
We compare the predictions of compositional models mantle transition zone to observed seismic properties by constructing phase diagrams in MgO‐FeO‐CaO‐Al 2 O 3 ‐SiO system and estimating elasticity relevant minerals. Mie‐Grüneisen Birch‐Murnaghan finite strain theory are combined with ideal solution extrapolate experimental measurements thermal elastic high pressures temperatures. The resulting thermodynamic potentials estimated predict density, parameter, adiabats for a given model. find...
The elastic constant tensors for the hcp phases of three transition metals (Co, Re, and Fe) are computed as functions pressure using Linearized Augmented Plane Wave method with both local density generalized gradient approximations. Spin-polarized states found to be stable Co (ferromagnetic) Fe (antiferromagnetic at low pressure). constants Re compared experimental measurements near ambient conditions excellent agreement is found. Recent lattice strain in high experiments when interpreted...
Terapascal iron-melting temperature The pressure and conditions at which iron melts are important for terrestrial planets because they determine the size of liquid metal core, an factor understanding potential generating a radiation-shielding magnetic field. Kraus et al . used laser-driven shock to iron-melt curve up 1000 gigapascals (see Perspective by Zhang Lin). This value is about three times that Earth’s inner core boundary. authors found lasted longest Earth-like four six larger in...
We use a new method to construct an upper mantle model based on self‐consistent computation of phase equilibria and physical properties. Computation the isotropic elastic wave velocities pyrolytic bulk composition in thermodynamic equilibrium shows distinct low‐velocity zone with minimum velocity V S = 4.47 km s −1 along 100 Ma geotherm. In vicinity this null hypothesis is approximated oceanic geotherms by 4.77 + 0.0380( P , z /29.80) − 0.000378( T 300), pressure GPa, depth km, temperature...
First-principles molecular-dynamics simulations show that over the pressure regime of Earth's mantle mean silicon-oxygen coordination number magnesium metasilicate liquid changes nearly linearly from 4 to 6. The density contrast between and crystal decreases by a factor 5 is 4% at core-mantle boundary. ab initio melting curve, obtained integration Clausius-Clapeyron equation, yields temperature boundary 5400 +/- 600 kelvins.
The elasticity of materials is important for our understanding processes ranging from brittle failure, to flexure, the propagation elastic waves. Seismologically revealed structure Earth's mantle, including radial (one‐dimensional) profile, lateral heterogeneity, and anisotropy are determined largely by that make up this region. Despite its importance geophysics, knowledge potentially relevant mineral phases at conditions typical mantle still limited: Measuring constants elevated...
A first principles theoretical approach shows that, at the density of inner core, both hexagonal [hexagonal close-packed (hcp)] and cubic [face-centered-cubic (fcc)] phases iron are substantially elastically anisotropic. forward model core based on predicted elastic constants assumption that consists a nearly perfectly aligned aggregate hcp crystals good agreement with seismic travel time anomalies have been attributed to anisotropy. cylindrically averaged fcc disagrees observations.
General potential linearized-augmented-plane-wave computations using the generalized-gradient approximation (GGA) of Perdew and Wang (PW-II) show excellent agreement with measured equations state bcc hcp phases to over 300 GPa, phase transition pressure, magnetic moment. The results are a significant improvement local-spin-density earlier PW-I GGA functional. is mechanically unstable at high pressure respect tetragonal strain, thus unlikely exist in earth's inner core.
We have carried out first-principles molecular dynamics simulations of silica liquid over a wide range pressure (from $0\phantom{\rule{0.3em}{0ex}}\text{to}\phantom{\rule{0.3em}{0ex}}\ensuremath{\sim}150\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$) and temperature $(3000--6000\phantom{\rule{0.3em}{0ex}}\mathrm{K})$ within density functional theory the pseudopotential approximation. Our results show that structure is highly sensitive to compression: average Si-O coordination number increases from...
Chemical heterogeneity, produced by the near-surface rock cycle and dominated volumetrically subducted oceanic crust its depleted residue, is continuously into mantle. This lithologic-scale chemical heterogeneity may survive in mantle for as long age of Earth because diffusion inefficient. Estimates rates subduction processing over geologic history indicate that most or all be composed lithologically heterogeneous material. Mineralogical models show many decades length scale detectable...
We combine first-principles calculations of forces with the direct nonequilibrium molecular dynamics method to determine lattice thermal conductivity $k$ periclase (MgO) up conditions representative Earth's core-mantle boundary (136 GPa, 4100 K). predict logarithmic density derivative $a=(\ensuremath{\partial}\mathrm{ln}k/\ensuremath{\partial}\mathrm{ln}\ensuremath{\rho}{)}_{T}=4.6\ifmmode\pm\else\textpm\fi{}1.2$ and that $k=20\ifmmode\pm\else\textpm\fi{}5\text{ }\text{...
We develop a self-consistent thermodynamic description of silicate liquids applicable across the entire mantle pressure and temperature regime. The combines finite strain free energy expansion with an account dependence liquid properties into single fundamental relation, while honouring expected limiting behaviour at large volume high temperature. find that relation describes well previous experimental theoretical results for MgO, MgSiO3, Mg2SiO4 SiO2. apply to calculate melting curves...
Understanding the chemical and thermal evolution of Earth requires knowledge transport properties silicate melts at high pressure temperature. Here, first-principles molecular dynamics simulations show that viscosity MgSiO3 liquid varies by two orders magnitude over mantle regime. Addition water systematically lowers viscosity, consistent with enhanced structural depolymerization. The combined effects temperature along model geotherms lead to a 10-fold increase in depth from surface base...
SUMMARY We derive exact expressions for the thermal expansivity, heat capacity and bulk modulus assemblages with arbitrarily large numbers of components phases, including influence phase transformations chemical exchange. illustrate results in simple two-component, two-phase systems, Mg–Fe olivine-wadsleyite Ca–Mg clinopyroxene-orthopyroxene a multicompontent model mantle composition form pyrolite. For latter we show expansivity over entire pressure–temperature regime to 40 GPa, or depth...
We investigate the thermoelastic properties of close-packed phases iron at pressures up to 400 GPa and temperature 6000 K using a tight-binding total-energy method cell model vibrational partition function. The calculated are in good agreement with available static shock-wave experimental measurements. compressional behavior number parameters is found resemble that prototypical oxide (MgO) supporting some aspects universal high compression: product thermal expansivity \ensuremath{\alpha}...
Analyses of x-ray-diffraction measurements on (Mg,Fe)SiO(3) perovskite and (Mg,Fe)O magnesiowüstite at simultaneous high temperature pressure are used to determine pressure-volume-temperature equations state thermoelastic properties these lower mantle minerals. Detailed comparison with the seismically observed density bulk sound velocity profiles does not support models this region that assume compositions identical upper mantle. The data consistent consisting nearly pure (>85 percent),...