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Mattesini, M., Belonoshko, A. & Tkalcic, H. (2018). Polymorphic Nature of Iron and Degree of Lattice Preferred Orientation Beneath the Earth's Inner Core Boundary. Geochemistry Geophysics Geosystems, 19(1), 292-304
Open this publication in new window or tab >>Polymorphic Nature of Iron and Degree of Lattice Preferred Orientation Beneath the Earth's Inner Core Boundary
2018 (English)In: Geochemistry Geophysics Geosystems, ISSN 1525-2027, E-ISSN 1525-2027, Vol. 19, no 1, p. 292-304Article in journal (Refereed) Published
Abstract [en]

Deciphering the polymorphic nature and the degree of iron lattice-preferred orientation in the Earth's inner core holds a key to understanding the present status and evolution of the inner core. A multiphase lattice-preferred orientation pattern is obtained for the top 350 km of the inner core by means of the ab initio based Candy Wrapper Velocity Model coupled to a Monte Carlo phase discrimination scheme. The achieved geographic distribution of lattice alignment is characterized by two regions of freezing, namely within South America and the Western Central Pacific, that exhibit an uncommon high degree of lattice orientation. In contrast, widespread regions of melting of relatively weak lattice ordering permeate the rest of the inner core. The obtained multiphase lattice-preferred orientation pattern is in line with mantle-constrained geodynamo simulations and allows to setup an ad hoc mineral physics scenario for the complex Earth's inner core. It is found that the cubic phase of iron is the dominating iron polymorph in the outermost part of the inner core.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION, 2018
Keywords
earth's inner core, lattice-preferred orientation, iron polymorphs
National Category
Geophysics
Identifiers
urn:nbn:se:kth:diva-224071 (URN)10.1002/2017GC007285 (DOI)000425633500016 ()2-s2.0-85041060388 (Scopus ID)
Note

QC 20180314

Available from: 2018-03-14 Created: 2018-03-14 Last updated: 2018-03-14Bibliographically approved
Fu, J., Zhao, J., Plyasunov, A. V. & Belonoshko, A. (2017). Ab initio molecular dynamics study of fluid H2O-CO2 mixture in broad pressure-temperature range. AIP Advances, 7(11), Article ID 115217.
Open this publication in new window or tab >>Ab initio molecular dynamics study of fluid H2O-CO2 mixture in broad pressure-temperature range
2017 (English)In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 7, no 11, article id 115217Article in journal (Refereed) Published
Abstract [en]

Properties of H2O and CO2 fluid and their mixtures under extreme pressures and temperatures are poorly known yet critically important in a number of applications. Several hundreds of first-principles molecular dynamics (FPMD) runs have been performed to obtain the pressure-volume-temperature (P-V-T) data on supercritical H2O, CO2, and H2O-CO2 mixtures. The pressure-temperature (P-T) range are from 0.5 GPa to 104 GPa (48.5 GPa for CO2) and from 600 K to 4000 K. Based on these data, we evaluate several existing equations of state (EOS) for the fluid H2O, CO2, and H2O-CO2 mixture. The results show that the EOS for H2O from Belonoshko et al. [Geochim. Cosmochim. Acta 55, 381-387; Geochim. Cosmochim. Acta 55, 3191-3208; Geochim. Cosmochim. Acta 56, 3611-3626; Comput. Geosci. 18, 1267-1269] not only can be used in the studied P-T range but also is accurate enough to be used for prediction of P-V-T data. In addition, IAPWS-95 EOS for H2O shows excellent extrapolation behavior beyond 1.0 GPa and 1273 K. However, for the case of CO2, none of the existing EOS produces data in agreement with the FPMD results. We created new EOS for CO2. The precision of the new EOS is tested by comparison to the calculated P-V-T data, fugacity coefficient of the CO2 fluid derived from high P-T experimental data as well as to the (very scarce) experimental volumetric data in the high P-T range. On the basis of our FPMD data we created a new EOS for H2O-CO2 mixture. The new EOS for the mixture is in reasonable agreement with experimental data.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-220283 (URN)10.1063/1.5006131 (DOI)000416825700067 ()2-s2.0-85035030472 (Scopus ID)
Note

QC 20171222

Available from: 2017-12-22 Created: 2017-12-22 Last updated: 2017-12-22Bibliographically approved
Gavryushkin, P. N., Popov, Z. I., Litasov, K. D., Belonoshko, A. & Gavryushkin, A. (2016). Stability of B2-type FeS at Earth's inner core pressures. Geophysical Research Letters, 43(16), 8435-8440
Open this publication in new window or tab >>Stability of B2-type FeS at Earth's inner core pressures
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2016 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 16, p. 8435-8440Article in journal (Refereed) Published
Abstract [en]

Using density functional theory, we investigated how substituting sulfur atoms for iron atoms affects the structure and energy of the body centered cubic and hexagonal close-packed iron phases at 350 GPa and at 0 K. We conclude that formation of random (Fe,S) solid solutions is energetically favorable in all intermediate compositions, although the random low-symmetry substitutions cause structural distortion. The (Fe,S) solid solution is nearly as favorable as the mechanical mixture of Fe-hcp and FeS-B2. This finding, in combination with dynamical stability, defines the B2 structure as a strong candidate for the sulfur-bearing phase of the Earth's inner core.

Place, publisher, year, edition, pages
Blackwell Publishing, 2016
Keywords
density functional theory, Earth's inner core, FeS, iron, sulfur, Crystal structure, Solid solutions, Stability, B2 structures, Body-centered cubic, Dynamical stability, Earth's inner cores, Hexagonal close-packed irons, Mechanical mixtures, Structural distortions, Sulfur atoms, Density functional theory
National Category
Geophysics
Identifiers
urn:nbn:se:kth:diva-194927 (URN)10.1002/2016GL069374 (DOI)000384443800013 ()2-s2.0-84983315352 (Scopus ID)
Note

QC 20161129

Available from: 2016-11-29 Created: 2016-11-01 Last updated: 2017-11-29Bibliographically approved
Lukinov, T., Rosengren, A., Martoňák, R. & Belonoshko, A. B. (2015). A metadynamics study of the fcc-bcc phase transition in Xenon at high pressure and temperature. Computational materials science, 107, 66-71, Article ID 6523.
Open this publication in new window or tab >>A metadynamics study of the fcc-bcc phase transition in Xenon at high pressure and temperature
2015 (English)In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 107, p. 66-71, article id 6523Article in journal (Refereed) Published
Abstract [en]

Abstract To theoretically find a stable solid phase is not a trivial task even at 0 K. The difficulties multiply at high temperature (T) because even more elaborate crystal structure prediction methods fail in the vicinity of the melting transition. Moreover, if the submelting phase is dynamically unstable at low T some methods cannot be applied at all. The method of metadynamics allows finding local minima of Gibbs free energy without additional simplifications. However, so far this method has been mainly used for study of pressure-induced solid-solid phase transitions and not in searching for T-induced ones. Here we study the applicability of the technique to the latter class of problems as well as to the approximate determination of the transition temperature. We apply the metadynamics method to study the solid-solid phase transition in Xe described by the Buckingham potential at high temperature and observe the fcc-bcc phase transition in a pressure-temperature range consistent with earlier results.

Keywords
Buckingham potential, Dynamical stability, Metadynamics, Solid-solid phase transition
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-170224 (URN)10.1016/j.commatsci.2015.04.055 (DOI)2-s2.0-84930945679 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20150630

Available from: 2015-06-30 Created: 2015-06-29 Last updated: 2017-12-04Bibliographically approved
Lukinov, T., Simak, S. I. & Belonoshko, A. B. (2015). Sound velocity in shock compressed molybdenum obtained by ab initio molecular dynamics. Physical Review B. Condensed Matter and Materials Physics, 92(6), Article ID 060101.
Open this publication in new window or tab >>Sound velocity in shock compressed molybdenum obtained by ab initio molecular dynamics
2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 6, article id 060101Article in journal (Refereed) Published
Abstract [en]

The sound velocity of Mo along the Hugoniot adiabat is calculated from first principles using density-functional theory based molecular dynamics. These data are compared to the sound velocity as measured in recent experiments. The theoretical and experimental Hugoniot and sound velocities are in very good agreement up to pressures of 210 GPa and temperatures of 3700 K on the Hugoniot. However, above that point the experiment and theory diverge. This implies that Mo undergoes a phase transition at about the same point. Considering that the melting point of Mo is likely much higher at that pressure, the related change in the sound velocity in experiment can be ascribed to a solid-solid transition.

National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-175935 (URN)10.1103/PhysRevB.92.060101 (DOI)000362212200001 ()2-s2.0-84941102577 (Scopus ID)
Funder
Swedish Research Council, 2013-5767Swedish Research Council, 2014-4750
Note

QC 20151103

Available from: 2015-11-03 Created: 2015-10-26 Last updated: 2017-12-01Bibliographically approved
Belonoshko, A. B., Lukinov, T., Rosengren, A., Bryk, T. & Litasov, K. D. (2015). Synthesis of heavy hydrocarbons at the core-mantle boundary. Scientific Reports, 5, Article ID 18382.
Open this publication in new window or tab >>Synthesis of heavy hydrocarbons at the core-mantle boundary
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2015 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, article id 18382Article in journal (Refereed) Published
Abstract [en]

The synthesis of complex organic molecules with C-C bonds is possible under conditions of reduced activity of oxygen. We have found performing ab initio molecular dynamics simulations of the C-O-H- Fe system that such conditions exist at the core-mantle boundary (CMB). H2O and CO2 delivered to the CMB by subducting slabs provide a source for hydrogen and carbon. The mixture of H2O and CO2 subjected to high pressure (130 GPa) and temperature (4000 to 4500 K) does not lead to synthesis of complex hydrocarbons. However, when Fe is added to the system, C-C bonds emerge. It means that oil might be a more abundant mineral than previously thought.

Place, publisher, year, edition, pages
Nature Publishing Group, 2015
National Category
Mineral and Mine Engineering
Identifiers
urn:nbn:se:kth:diva-180487 (URN)10.1038/srep18382 (DOI)000366571400001 ()26675747 (PubMedID)2-s2.0-84950349897 (Scopus ID)
Note

QC 20160115

Available from: 2016-01-15 Created: 2016-01-14 Last updated: 2017-11-30Bibliographically approved
Belonoshko, A. B., Ramzan, M., Mao, H.-k. & Ahuja, R. (2013). Atomic Diffusion in Solid Molecular Hydrogen. Scientific Reports, 3, 2340
Open this publication in new window or tab >>Atomic Diffusion in Solid Molecular Hydrogen
2013 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 3, p. 2340-Article in journal (Refereed) Published
Abstract [en]

We performed ab initio molecular dynamics simulations of the C2c and Cmca-12 phases of hydrogen at pressures from 210 to 350 GPa. These phases were predicted to be stable at 0 K and pressures above 200 GPa. However, systematic studies of temperature impact on properties of these phases have not been performed so far. Filling this gap, we observed that on temperature increase diffusion sets in the Cmca-12 phase, being absent in C2c. We explored the mechanism of diffusion and computed melting curve of hydrogen at extreme pressures. The results suggest that the recent experiments claiming conductive hydrogen at the pressure around 260 GPa and ambient temperature might be explained by the diffusion. The diffusion might also be the reason for the difference in Raman spectra obtained in recent experiments.

Keywords
Augmented-Wave Method, Dense Hydrogen, Charge-Transfer, Melting Curves, Gpa
National Category
Engineering and Technology
Identifiers
urn:nbn:se:kth:diva-127497 (URN)10.1038/srep02340 (DOI)000322565300003 ()2-s2.0-84881332739 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20130902

Available from: 2013-09-02 Created: 2013-08-30 Last updated: 2017-12-06Bibliographically approved
Benazzouz, B. K., Zaoui, A. & Belonoshko, A. B. (2013). Determination of the melting temperature of kaolinite by means of the Z-method. American Mineralogist, 98(10), 1881-1885
Open this publication in new window or tab >>Determination of the melting temperature of kaolinite by means of the Z-method
2013 (English)In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 98, no 10, p. 1881-1885Article in journal (Refereed) Published
Abstract [en]

The melting temperature of materials is an important thermodynamic property. Despite the importance of kaolinite, one of the most common clay minerals on the Earth's surface, its thermal and melting behavior is poorly understood. We apply here the Z-method to determine the melting temperature (T-m) and the limit of superheating (T-LS) of kaolinite. The T-m is found at 1818 K (8.85 GPa), and T-LS at 1971 K (6.8 GPa). The diffusion coefficient for all atoms has been calculated in a broad temperature range. The calculated characteristics and, in particular, their dependence on temperature have confirmed the solid-liquid transition and strongly support the calculated melting point. In addition, some computed quantities, such as the radial distribution function, coordination numbers and mean-square displacement, were used to confirm the liquid state of kaolinite from the melting temperature as well as at other temperatures in the liquid branch. The diffusion coefficient for different atoms has been calculated throughout the isochore. These quantities and in particular their evolution under temperature have confirmed the solid-liquid states of kaolinite and the presence of the melting point. The latter quantity constitutes the first ever melting simulation of a clay mineral with close agreement to the experimental one.

Keywords
Kaolinite, melting, molecular dynamics, Z-method
National Category
Geophysics
Identifiers
urn:nbn:se:kth:diva-134743 (URN)10.2138/am.2013.4379 (DOI)000326357400025 ()2-s2.0-84885055993 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20131203

Available from: 2013-12-03 Created: 2013-11-28 Last updated: 2017-12-06Bibliographically approved
Lukinov, T., Rosengren, A. & Belonoshko, A. B. (2013). Impact of crystal lattice defects on crystal melting: A molecular dynamics study. Computational materials science, 79, 95-98
Open this publication in new window or tab >>Impact of crystal lattice defects on crystal melting: A molecular dynamics study
2013 (English)In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 79, p. 95-98Article in journal (Refereed) Published
Abstract [en]

An ideal infinite lattice, when subjected to heating does not melt at the thermodynamic melting temperature. Instead, it remains solid metastably up to considerably higher temperatures. This effect is called superheating. We performed a molecular dynamics simulation of Xenon using Lennard-Jonesium potential with several types of defects. We observed a superheating effect on the chosen model for several pressures and found that the presence of grain inclusion or grain interface eliminates the superheating effect.

Keywords
Superheating, Overheating, Lennard-Jonesium, Melting
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-132197 (URN)10.1016/j.commatsci.2013.06.026 (DOI)000324471100014 ()2-s2.0-84879937895 (Scopus ID)
Note

QC 20131024

Available from: 2013-10-24 Created: 2013-10-24 Last updated: 2017-12-06Bibliographically approved
Ruban, A. V., Belonoshko, A. B. & Skorodumova, N. V. (2013). Impact of magnetism on Fe under Earth's core conditions. Physical Review B. Condensed Matter and Materials Physics, 87(1), 014405
Open this publication in new window or tab >>Impact of magnetism on Fe under Earth's core conditions
2013 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, no 1, p. 014405-Article in journal (Refereed) Published
Abstract [en]

Using a microscopic phenomenological model for longitudinal spin fluctuations (LSFs) based on density functional theory calculations, we demonstrate that under the Earth's core conditions (P approximate to 360 GPa, T approximate to 6000 K), Fe acquires substantial local magnetic moment, up to 1.3 mu(B), for different crystal structure modifications. We demonstrate that the LSFs produce a substantial effect on the magnetic and thermodynamic properties of iron, in particular, its equilibrium volume under solid Earth's core conditions.

Keywords
Inner-Core, 1st-Principles Theory, Potential Model, High-Pressures, Electron-Gas, Iron, Alloys, Phase, Approximation, Temperatures
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-117636 (URN)10.1103/PhysRevB.87.014405 (DOI)000313029600004 ()2-s2.0-84872223269 (Scopus ID)
Funder
Swedish Research Council, 2009-3619 2010-3187VinnovaEU, European Research Council, 228074
Note

QC 20130201

Available from: 2013-02-01 Created: 2013-02-01 Last updated: 2017-12-06Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-7531-3210

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