Physics of iron at Earth's core conditions

The bulk properties of iron at the pressure and temperature conditions of Earth's core were determined by a method that combines first-principles and classical molecular dynamic simulations. The theory indicates that (i) the iron melting temperature at inner-core boundary (ICB) pressure (330 gigapascals) is 5400 (+/-400) kelvin; (ii) liquid iron at ICB conditions is about 6% denser than Earth's outer core; and (iii) the shear modulus of solid iron close to its melting line is 140 gigapascals, consistent with the seismic value for the inner core. These results reconcile melting temperature estimates based on sound velocity shock wave data with those based on diamond anvil cell experiments.

[1]  R. Ahuja,et al.  Embedded-atom molecular dynamic study of iron melting , 1997 .

[2]  O. Anderson,et al.  The case for a body-centered cubic phase (α′) for iron at inner core conditions , 1997 .

[3]  R. Jeanloz,et al.  The Melting Curve of Iron to 250 Gigapascals: A Constraint on the Temperature at Earth's Center , 1987, Science.

[4]  H. Mao,et al.  Melting and crystal structure of iron at high pressures and temperatures , 1998 .

[5]  Role of layering oscillations at liquid metal surfaces in bulk recrystallization and surface melting. , 1995, Physical review letters.

[6]  J. Poirier.  Light elements in the Earth's outer core: A critical review , 1994 .

[7]  R. Boehler.  Melting of mantle and core materials at very high pressures , 1996, Philosophical Transactions of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[8]  H. Mao,et al.  Static compression of iron to 300 GPa and Fe(0.8)Ni(0.2) alloy to 260 GPa - Implications for composition of the core , 1990 .

[9]  Ross,et al.  Shock temperatures and melting of iron at Earth core conditions. , 1993, Physical review letters.

[10]  Wills,et al.  First-principles theory of iron up to earth-core pressures: Structural, vibrational, and elastic properties. , 1996, Physical review. B, Condensed matter.

[11]  Jeroen Tromp,et al.  Support for anisotropy of the Earth's inner core from free oscillations , 1993, Nature.

[12]  A. Becke,et al.  Density-functional exchange-energy approximation with correct asymptotic behavior. , 1988, Physical review. A, General physics.

[13]  J. Poirier,et al.  Dislocation melting of iron and the temperature of the inner core boundary, revisited , 1993 .

[14]  H. Mao,et al.  Elasticity and rheology of iron above 220 GPa and the nature of the Earth's inner core , 1998, Nature.

[15]  M. Parrinello,et al.  Strain fluctuations and elastic constants , 1982 .

[16]  M. Gillan,et al.  The melting curve of iron at the pressures of the Earth's core from ab initio calculations , 1999, Nature.

[17]  M. Baskes,et al.  Modified embedded-atom potentials for cubic materials and impurities. , 1992, Physical review. B, Condensed matter.

[18]  A. Dziewoński,et al.  Solidity of the Inner Core of the Earth inferred from Normal Mode Observations , 1971, Nature.

[19]  J. Perdew,et al.  Density-functional approximation for the correlation energy of the inhomogeneous electron gas. , 1986, Physical review. B, Condensed matter.

[20]  J. Tallon.  The volume dependence of elastic moduli and the Born-Durand melting hypothesis , 1979 .

[21]  A. Belonoshko.  Atomistic Simulation of Shock Wave-Induced Melting in Argon , 1997, Science.

[22]  P. Olson,et al.  Is the inner core of the Earth pure iron? , 1987, Nature.

[23]  H. Mao,et al.  Correction: Elasticity and rheology of iron above 220 GPa and the nature of the Earth's inner core , 1998, Nature.

[24]  M. Gillan,et al.  First-order phase transitions by first-principles free-energy calculations: the melting of Al , 1998 .

[25]  D. L. Anderson,et al.  Preliminary reference earth model , 1981 .

[26]  R. Cohen,et al.  High-Pressure Elasticity of Iron and Anisotropy of Earth's Inner Core , 1995, Science.

[27]  J. Cannon.  Behavior of the Elements at High Pressures , 1974 .

[28]  G. Shen,et al.  Temperatures in Earth's Core Based on Melting and Phase Transformation Experiments on Iron , 1994, Science.

[29]  M. Gillan,et al.  The viscosity of liquid iron at the physical conditions of the Earth's core , 1998, Nature.

[30]  R. Boehler.  Temperatures in the Earth's core from melting-point measurements of iron at high static pressures , 1993, Nature.

[31]  R. Jeanloz.  The nature of the earth's core , 1990 .

[32]  N. Mermin.  Thermal Properties of the Inhomogeneous Electron Gas , 1965 .

[33]  O. Anderson,et al.  Experimental melting curve of iron revisited , 1997 .

[34]  G. Steinle-Neumann,et al.  First-principles elastic constants for the hcp transition metals Fe, Co, and Re at high pressure (vol 60, pg 791, 1999) , 1999 .

[35]  W. Bassett.  What Is in the Earth's Core Besides Iron? , 1994, Science.

[36]  J. Brown,et al.  The electronic band structures of iron, sulfur, and oxygen at high pressures and the Earth's core , 1990 .

[37]  R. Cohen,et al.  Composition and temperature of Earth's inner core , 1997 .

[38]  R. Mcqueen,et al.  Phase transitions, Grüneisen parameter, and elasticity for shocked iron between 77 GPa and 400 GPa , 1986 .