Quenching of bcc-Fe from high to room temperature at high-pressure conditions: a molecular dynamics simulation

Belonoshko, Anatoly B.; Derlet, P. M.; Mikhaylushkin, A. S.; Simak, Sergei I.; Hellman, Olle; Burakovsky, Leonid; Swift, Damian; Johansson, Börje

doi:10.1088/1367-2630/11/9/093039

Cited by 23 publications

(12 citation statements)

References 23 publications

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“…Here we review theoretical evidence pointing to bcc iron being unstable at 0.3-1.5TPa based on first-principles calculations, both for the static lattice and via molecular dynamics. The strongest arguments for high temperature stabilizing bcc Fe resulted from use of classical manybody potentials (Belonoshko et al, 2003(Belonoshko et al, , 2007(Belonoshko et al, , 2008(Belonoshko et al, , 2009, and misinterpretation of the requirements of mechanical stability in prior simulations (Vocadlo et al, 2003;Belonoshko et al, 2006 ;Bouchet et al, 2013). We show that these studies suffer from the use of approximate potentials, the accuracy of which is untested, and from focusing on the hydrostatic nature of the stresses for inferring mechanical stability.…”

Section: Introductionmentioning

confidence: 96%

“…There has been longstanding controversy about the stable crystalline phases of iron at pressures of 300-1500 GPa (0.3-1.5 TPa ≈ 3-15 Mbar), with claims that the body-centered cubic(bcc)structure may be stable at temperatures close to the melting point (Brown and McQueen, 1986;Boehler, 1993;Dubrowinsky et al, 2007;Ross et al, 19990 ;Vocadlo et al, 2003;Belonoshko et al, 2003;Vocadlo et al, 2008;Luo, et al, 2010;Kong et al, 2012 ;Belonoshko et al, 2006Belonoshko et al, , 2007Belonoshko et al, , 2008Belonoshko et al, , 2009Bouchetet al, 2013). The theoretical rationale is that entropy associated with atomic vibrations might stabilize the bcc relative to close-packed structures at combined high pressures and temperatures.…”

Section: Introductionmentioning

confidence: 99%

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Stability of iron crystal structures at 0.3–1.5 TPa

Godwal

González‐Cataldo

Verma

et al. 2015

Earth and Planetary Science Letters

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Ab initio molecular dynamics simulations carried out for tetragonal and orthorhombic distortions of iron closely follow the results of static-lattice electronic-structure calculations in revealing that the body-centered cubic (bcc) phase of Fe is mechanically unstable at pressures of 0.3-1.5 TPa and temperatures up to 7000 K. Crystal-structural instabilities originate in the static lattice for the bcc configuration, and are consistent with recent results from both static and dynamic highpressure experiments. Both theory and experiment thus show that it is the close-packed (hexagonal, hcp and face-centered cubic, fcc) crystal structures of iron that are relevant to the cores of Earth-like planets.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Stability of iron crystal structures at 0.3–1.5 TPa

Godwal

González‐Cataldo

Verma

et al. 2015

Earth and Planetary Science Letters

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“…In fact, the use of EAM-type potentials is still a mainstay for detailed atomistic simulations in a variety of practical contexts (e.g. [22,23,[36][37][38]), but systematic examination of the model potentials are hardly carried out beyond zero temperature. Müller et al [24] indeed pursued a conventional fitting-based approach to model the temperature dependence of the phase stability of iron, employing an Abell-Tersoff-Brenner (ATB)-type bond-order potential with angular dependences [39][40][41][42], which falls into an equivalent class of the second-moment description of EAM.…”

Section: Introductionmentioning

confidence: 99%

Atomistic modeling of thermodynamic equilibrium and polymorphism of iron

Lee

Baskes

Valone

et al. 2012

J. Phys.: Condens. Matter

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We develop two new modified embedded-atom method (MEAM) potentials for elemental iron, intended to reproduce the experimental phase stability with respect to both temperature and pressure. These simple interatomic potentials are fitted to a wide variety of material properties of bcc iron in close agreement with experiments. Numerous defect properties of bcc iron and bulk properties of the two close-packed structures calculated with these models are in reasonable agreement with the available first-principles calculations and experiments. Performance at finite temperatures of these models has also been examined using Monte Carlo simulations. We attempt to reproduce the experimental iron polymorphism at finite temperature by means of free energy computations, similar to the procedure previously pursued by Müller et al (2007 J. Phys.: Condens. Matter 19 326220), and re-examine the adequacy of the conclusion drawn in the study by addressing two critical aspects missing in their analysis: (i) the stability of the hcp structure relative to the bcc and fcc structures and (ii) the compatibility between the temperature and pressure dependences of the phase stability. Using two MEAM potentials, we are able to represent all of the observed structural phase transitions in iron. We discuss that the correct reproductions of the phase stability among three crystal structures of iron with respect to both temperature and pressure are incompatible with each other due to the lack of magnetic effects in this class of empirical interatomic potential models. The MEAM potentials developed in this study correctly predict, in the bcc structure, the self-interstitial in the (110) orientation to be the most stable configuration, and the screw dislocation to have a non-degenerate core structure, in contrast to many embedded-atom method potentials for bcc iron in the literature.

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“…[7]. It was attempted to explain this behavior by a temperature induced solid-solid transition (Fe [8], Mo [9], Ta [10], Xe [11]). The stable phase of Xe at normal conditions is the face centered cubic (fcc) lattice.…”

Section: Introductionmentioning

confidence: 99%