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Nguyen-Cong, K., Willman, J. T., Gonzalez, J. M., Williams, A. S., Belonoshko, A., Moore, S. G., . . . Oleynik, I. I. (2024). Extreme Metastability of Diamond and its Transformation to the BC8 Post-Diamond Phase of Carbon. The Journal of Physical Chemistry Letters, 15(4), 1152-1160
Open this publication in new window or tab >>Extreme Metastability of Diamond and its Transformation to the BC8 Post-Diamond Phase of Carbon
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2024 (English)In: The Journal of Physical Chemistry Letters, E-ISSN 1948-7185, Vol. 15, no 4, p. 1152-1160Article in journal (Refereed) Published
Abstract [en]

Diamond possesses exceptional physical properties due to its remarkably strong carbon-carbon bonding, leading to significant resilience to structural transformations at very high pressures and temperatures. Despite several experimental attempts, synthesis and recovery of the theoretically predicted post-diamond BC8 phase remains elusive. Through quantum-accurate multimillion atom molecular dynamics (MD) simulations, we have uncovered the extreme metastability of diamond at very high pressures, significantly exceeding its range of thermodynamic stability. We predict the post-diamond BC8 phase to be experimentally accessible only within a narrow high pressure-temperature region of the carbon phase diagram. The diamond to BC8 transformation proceeds through premelting followed by BC8 nucleation and growth in the metastable carbon liquid. We propose a double-shock compression pathway for BC8 synthesis, which is currently being explored in experiments at the National Ignition Facility.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2024
National Category
Inorganic Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-343466 (URN)10.1021/acs.jpclett.3c03044 (DOI)001156044600001 ()38269426 (PubMedID)2-s2.0-85184145622 (Scopus ID)
Note

QC 20240216

Available from: 2024-02-15 Created: 2024-02-15 Last updated: 2024-07-04Bibliographically approved
Belonoshko, A. & Smirnov, G. S. S. (2023). A Comparison of Experimental and Ab Initio Structural Data on Fe under Extreme Conditions. Metals, 13(6), Article ID 1096.
Open this publication in new window or tab >>A Comparison of Experimental and Ab Initio Structural Data on Fe under Extreme Conditions
2023 (English)In: Metals, ISSN 2075-4701, Vol. 13, no 6, article id 1096Article in journal (Refereed) Published
Abstract [en]

Iron is the major element of the Earth's core and the cores of Earth-like exoplanets. The crystal structure of iron, the major component of the Earth's solid inner core (IC), is unknown under the high pressures (P) (3.3-3.6 Mbar) and temperatures (T) (5000-7000 K) and conditions of the IC and exoplanetary cores. Experimental and theoretical data on the phase diagram of iron at these extreme PT conditions are contradictory. Though some of the large-scale ab initio molecular dynamics (AIMD) simulations point to the stability of the body-centered cubic (bcc) phase, the latest experimental data are often interpreted as evidence for the stability of the hexagonal close-packed (hcp) phase. Applying large-scale AIMD, we computed the properties of iron phases at the experimental pressures and temperatures reported in the experimental papers. The use of large-scale AIMD is critical since the use of small bcc computational cells (less than approximately 1000 atoms) leads to the collapse of the bcc structure. Large-scale AIMD allowed us to compare the measured and computed coordination numbers as well as the measured and computed structural factors. This comparison, in turn, allowed us to suggest that the computed density, coordination number, and structural factors of the bcc phase are in agreement with those observed in experiments, which were previously assigned either to the liquid or hcp phase.

Place, publisher, year, edition, pages
MDPI AG, 2023
Keywords
iron, molecular dynamics, ab initio
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-331825 (URN)10.3390/met13061096 (DOI)001014948600001 ()
Note

QC 20230714

Available from: 2023-07-14 Created: 2023-07-14 Last updated: 2023-07-14Bibliographically approved
Yin, K., Belonoshko, A., Li, Y. & Lu, X. (2023). Davemaoite as the mantle mineral with the highest melting temperature. Science Advances, 9(49), Article ID eadj2660.
Open this publication in new window or tab >>Davemaoite as the mantle mineral with the highest melting temperature
2023 (English)In: Science Advances, E-ISSN 2375-2548, Vol. 9, no 49, article id eadj2660Article in journal (Refereed) Published
Abstract [en]

Knowledge of high-pressure melting curves of silicate minerals is critical for modeling the thermal-chemical evolution of rocky planets. However, the melting temperature of davemaoite, the third most abundant mineral in Earth's lower mantle, is still controversial. Here, we investigate the melting curves of two minerals, MgSiO3 bridgmanite and CaSiO3 davemaoite, under their stability field in the mantle by performing first-principles molecular dynamics simulations based on the density functional theory. The melting curve of bridgmanite is in excellent agreement with previous studies, confirming a general consensus on its melting temperature. However, we predict a much higher melting curve of davemaoite than almost all previous estimates. Melting temperature of davemaoite at the pressure of core-mantle boundary (similar to 136 gigapascals) is about 7700(150) K, which is approximately 2000 K higher than that of bridgmanite. The ultrarefractory nature of davemaoite is critical to reconsider many models in the deep planetary interior, for instance, solidification of early magma ocean and geodynamical behavior of mantle rocks.

Place, publisher, year, edition, pages
American Association for the Advancement of Science (AAAS), 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-342330 (URN)10.1126/sciadv.adj2660 (DOI)001116516600012 ()38055828 (PubMedID)2-s2.0-85179017150 (Scopus ID)
Note

QC 20240116

Available from: 2024-01-16 Created: 2024-01-16 Last updated: 2024-01-16Bibliographically approved
Belonoshko, A., Simak, S. I., Olovsson, W. & Vekilova, O. Y. (2022). Elastic properties of body-centered cubic iron in Earth's inner core. Physical Review B, 105(18), Article ID L180102.
Open this publication in new window or tab >>Elastic properties of body-centered cubic iron in Earth's inner core
2022 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 105, no 18, article id L180102Article in journal (Refereed) Published
Abstract [en]

The solid Earth's inner core (IC) is a sphere with a radius of about 1300 km in the center of the Earth. The information about the IC comes mainly from seismic studies. The composition of the IC is obtained by matching the seismic data and properties of candidate phases subjected to high pressure (P) and temperature (T). The close match between the density of the IC and iron suggests that the main constituent of the IC is iron. However, the stable phase of iron is still a subject of debate. One such iron phase, the body-centered cubic phase (bcc), is dynamically unstable at pressures of the IC (330-364 GPa) and low T but gets stabilized at high T characteristic of the IC (5000-7000 K). So far, ab initio molecular dynamics (AIMD) studies attempted to compute the bcc elastic properties for a small (order of 102) number of atoms. The mechanism of the bcc stabilization cannot be enabled in such cells and that has led to erroneous results. Here we apply AIMD to compute elastic moduli and sound velocities of the Fe bcc phase for a 2000 Fe atom computational cell, which is a cell of unprecedented size for ab initio calculations of iron. Unlike in previous ab initio calculations, both the longitudinal and the shear sound velocities of the Fe bcc phase closely match the properties of the IC material at P = 360 GPa and T = 6600 K, likely the PT conditions in the IC. The calculated density of the bcc iron at these PT conditions is just 3% higher than the density of the IC material according to the Preliminary Earth Model. This suggests that the widely assumed amount of light elements in the IC may need a reconsideration. The anisotropy of the bcc phase is an exact match to the most recent seismic studies. 

Place, publisher, year, edition, pages
American Physical Society (APS), 2022
Keywords
Acoustic wave velocity, Atoms, Calculations, Elasticity, Integrated circuits, Molecular dynamics, Seismology, Shear flow, Ab initio calculations, Ab initio molecular dynamics, Body-centered-cubic phase, Condition, Core material, Earth inner core, Elastic properties, Inner core, Property, Seismic studies, Iron
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-324372 (URN)10.1103/PhysRevB.105.L180102 (DOI)000808325000002 ()2-s2.0-85131356321 (Scopus ID)
Note

QC 20230228

Available from: 2023-02-28 Created: 2023-02-28 Last updated: 2023-02-28Bibliographically approved
Willman, J. T., Nguyen-Cong, K., Williams, A. S., Belonoshko, A., Moore, S. G., Thompson, A. P., . . . Oleynik, I. I. (2022). Machine learning interatomic potential for simulations of carbon at extreme conditions. Physical Review B, 106(18), Article ID L180101.
Open this publication in new window or tab >>Machine learning interatomic potential for simulations of carbon at extreme conditions
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2022 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 106, no 18, article id L180101Article in journal (Refereed) Published
Abstract [en]

A spectral neighbor analysis (SNAP) machine learning interatomic potential (MLIP) has been developed for simulations of carbon at extreme pressures (up to 5 TPa) and temperatures (up to 20 000 K). This was achieved using a large database of experimentally relevant quantum molecular dynamics (QMD) data, training the SNAP potential using a robust machine learning methodology, and performing extensive validation against QMD and experimental data. The resultant carbon MLIP demonstrates unprecedented accuracy and transferability in predicting the carbon phase diagram, melting curves of crystalline phases, and the shock Hugoniot, all within 3% of QMD. By achieving quantum accuracy and efficient implementation on leadership-class high-performance computing systems, SNAP advances frontiers of classical MD simulations by enabling atomic-scale insights at experimental time and length scales.

Place, publisher, year, edition, pages
American Physical Society (APS), 2022
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-323593 (URN)10.1103/PhysRevB.106.L180101 (DOI)000908068300002 ()2-s2.0-85143815449 (Scopus ID)
Note

QC 20230208

Available from: 2023-02-08 Created: 2023-02-08 Last updated: 2023-02-08Bibliographically approved
Nguyen-Cong, K., Willman, J. T., Moore, S. G., Belonoshko, A., Gayatri, R., Weinberg, E., . . . Oleynik, I. I. (2021). Billion atom molecular dynamics simulations of carbon at extreme conditions and experimental time and length scales. In: SC '21: Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis: . Paper presented at 33rd International Conference for High Performance Computing, Networking, Storage and Analysis: Science and Beyond, SC 2021, 14 November 2021 through 19 November 2021. Association for Computing Machinery (ACM)
Open this publication in new window or tab >>Billion atom molecular dynamics simulations of carbon at extreme conditions and experimental time and length scales
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2021 (English)In: SC '21: Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis, Association for Computing Machinery (ACM) , 2021Conference paper, Published paper (Refereed)
Abstract [en]

Billion atom molecular dynamics (MD) using quantum-Accurate machine-learning Spectral Neighbor Analysis Potential (SNAP) observed long-sought high pressure BC8 phase of carbon at extreme pressure (12 Mbar) and temperature (5,000 K). 24-hour, 4650 node production simulation on OLCF Summit demonstrated an unprecedented scaling and unmatched real-world performance of SNAP MD while sampling 1 nanosecond of physical time. Efficient implementation of SNAP force kernel in LAMMPS using the Kokkos CUDA backend on NVIDIA GPUs combined with excellent strong scaling (better than 97% parallel efficiency) enabled a peak computing rate of 50.0 PFLOPs (24.9% of theoretical peak) for a 20 billion atom MD simulation on the full Summit machine (27,900 GPUs). The peak MD performance of 6.21 Matom-steps/node-s is 22.9 times greater than a previous record for quantum-Accurate MD. Near perfect weak scaling of SNAP MD highlights its excellent potential to advance the frontier of quantum-Accurate MD to trillion atom simulations on upcoming exascale platforms.

Place, publisher, year, edition, pages
Association for Computing Machinery (ACM), 2021
Series
International Conference for High Performance Computing, Networking, Storage and Analysis, SC, ISSN 2167-4329
Keywords
carbon, extreme conditions, machine-learning interatomic potentials, molecular dynamics
National Category
Software Engineering
Identifiers
urn:nbn:se:kth:diva-312842 (URN)10.1145/3458817.3487400 (DOI)000946520100095 ()2-s2.0-85117901197 (Scopus ID)
Conference
33rd International Conference for High Performance Computing, Networking, Storage and Analysis: Science and Beyond, SC 2021, 14 November 2021 through 19 November 2021
Note

QC 20220602

Part of proceedings: ISBN 978-145038442-1

Available from: 2022-06-02 Created: 2022-06-02 Last updated: 2023-09-21Bibliographically approved
Belonoshko, A., Fu, J. & Smirnov, G. (2021). Free energies of iron phases at high pressure and temperature: Molecular dynamics study. Physical Review B, 104(10), Article ID 104103.
Open this publication in new window or tab >>Free energies of iron phases at high pressure and temperature: Molecular dynamics study
2021 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 104, no 10, article id 104103Article in journal (Refereed) Published
Abstract [en]

The crystal structure of iron, the major component of the Earth's inner core (IC), is unknown under the IC high pressure (P) (3.3-3.6 Mbar) and temperature (T) (5000-7000 K). Experimental and theoretical data on the phase diagram of iron at these extreme PT conditions are contradictory. Applying quasi-ab initio and ab initio molecular dynamics we computed free energies of the body-centered cubic (bcc), hexagonal close-packed (hcp), and liquid phases. The ionic free energies, computed for the embedded-atom model, were corrected for electronic entropy. Such correction brings the melting temperatures of the hcp iron in very good agreement with previous ab initio data. This validates the calculation of the bcc phase, where fully ab initio treatment is not technically possible due to large sizes required for convergence. The resulting phase diagram shows stabilization of the bcc phase prior to melting in the pressure range of the IC. The melting temperature of the bcc phase is equal to 7190 K at the pressure 360 GPa.

Place, publisher, year, edition, pages
American Physical Society (APS), 2021
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-302596 (URN)10.1103/PhysRevB.104.104103 (DOI)000696017900001 ()2-s2.0-85114858326 (Scopus ID)
Note

QC 20211027

Available from: 2021-10-27 Created: 2021-10-27 Last updated: 2022-06-25Bibliographically approved
Gavryushkin, P. N., Belonoshko, A., Sagatov, N., Sagatova, D., Zhitova, E., Krzhizhanovskaya, M. G., . . . Litasov, K. D. (2021). Metastable structures of CaCO3 and their role in transformation of calcite to aragonite and postaragonite. Crystal Growth & Design, 21(1), 65-74
Open this publication in new window or tab >>Metastable structures of CaCO3 and their role in transformation of calcite to aragonite and postaragonite
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2021 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 21, no 1, p. 65-74Article in journal (Refereed) Published
Abstract [en]

Using molecular dynamics simulation and evolutionary metadynamic calculations, a series of structures were revealed that possessed enthalpies and Gibbs energies lower than those of aragonite but higher than those of calcite. The structures are polytypes of calcite, differing in the stacking sequence of close packed (cp) Ca layers. The two- and six-layered polytypes have hexagonal symmetry P6(3)22 and were named hexarag and hexite, respectively. Hexarag is similar to aragonite, but with all the triangles placed on the middle distance between the cp layers. On the basis of the structures found, a two-step mechanism for the transformation of aragonite to calcite is suggested. In the first step, CO3 triangles migrate to halfway between the Ca layers with the formation of hexarag. In the second step, the two-layered cp (hcp) hexarag structure transforms into three-layered cp (fcc) calcite through a series of many-layered polytypes. The topotactic character of the transformation of aragonite to calcite, with [001] of aragonite being parallel to [0001] of calcite, is consistent with the suggested mechanism. High-temperature X-ray powder diffraction experiments did not reveal hexarag reflections. To assess the possibility of the formation of the polytypes found in nature or experiments, a TEM analysis of ground aragonite was performed. A grain was found that had six superstructure reflections in a direction perpendicular to the plane of the cp layer. This grain is believed to correspond to one of the predicted polytypes, with the diffuse character of the diffraction spots indicating a partial disordering of the cp layer stacking. A topological analysis was also performed, along with energy calculations, of the metastable high-pressure polymorphs CaCO3-II, -III, -Mb, and -VI. The similarity of CaCO3-II, -II, and -Mb to the calcite structure and the small energy difference explain the metastable formation of these polymorphs during the cold compression of calcite. On the basis of the performed analysis, the evolution of the CaCO3 cation array at calcite to a post-aragonite transformation is described.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2021
National Category
Earth and Related Environmental Sciences
Identifiers
urn:nbn:se:kth:diva-291079 (URN)10.1021/acs.cgd.0c00589 (DOI)000607623900010 ()2-s2.0-85098763726 (Scopus ID)
Note

QC 20210301

Available from: 2021-03-01 Created: 2021-03-01 Last updated: 2022-06-25Bibliographically approved
Fu, J., Cao, L., Duan, X. & Belonoshko, A. B. (2020). Density and sound velocity of liquid Fe-S alloys at Earth's outer core P-T conditions. American Mineralogist, 105(9), 1349-1354
Open this publication in new window or tab >>Density and sound velocity of liquid Fe-S alloys at Earth's outer core P-T conditions
2020 (English)In: American Mineralogist, ISSN 0003-004X, E-ISSN 1945-3027, Vol. 105, no 9, p. 1349-1354Article in journal (Refereed) Published
Abstract [en]

Pressure-temperature-volume (P-T-V) data on liquid iron-sulfur (Fe-S) alloys at the Earth's outer core conditions (similar to 136 to 330 GPa, similar to 4000 to 7000 K) have been obtained by first-principles molecular dynamics simulations. We developed a thermal equation of state (EoS) composed of Murnaghan and Mie-Gruneisen-Debye expressions for liquid Fe-S alloys. The density and sound velocity are calculated and compared with Preliminary Reference Earth Model (PREM) to constrain the S concentration in the outer core. Since the temperature at the inner core boundary (TICB) has not been measured precisely (4850 similar to 7100 K), we deduce that the S concentration ranges from 10 similar to 14 wt% assuming S is the only light element. Our results also show that Fe-S alloys cannot satisfy the seismological density and sound velocity simultaneously and thus S element is not the only light element. Considering the geophysical and geochemical constraints, we propose that the outer core contains no more than 3.5 wt%S, 2.5 wt%O, or 3.8 wt% Si. In addition, the developed thermal EoS can be utilized to calculate the thermal properties of liquid Fe-S alloys, which may serve as the fundamental parameters to model the Earth's outer core.

Place, publisher, year, edition, pages
MINERALOGICAL SOC AMER, 2020
Keywords
Earth's outer core, liquid Fe-S alloy, first-principles molecular dynamics, sound velocity, equation of state
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-284284 (URN)10.2138/am-2020-7349 (DOI)000573885100007 ()2-s2.0-85093098532 (Scopus ID)
Note

QC 20201026

Available from: 2020-10-26 Created: 2020-10-26 Last updated: 2024-03-15Bibliographically approved
Gavryushkin, P. N., Sagatov, N., Belonoshko, A., Banaev, M. V. & Litasov, K. D. (2020). Disordered Aragonite: The New High-Pressure, High-Temperature Phase of CaCO3. The Journal of Physical Chemistry C, 124(48), 26467-26473
Open this publication in new window or tab >>Disordered Aragonite: The New High-Pressure, High-Temperature Phase of CaCO3
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2020 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 124, no 48, p. 26467-26473Article in journal (Refereed) Published
Abstract [en]

Phases of CaCO3 stabilized at high pressures and temperatures are the potential agents of the global carbon cycle, transferring oxidized carbon in deep Earth's interiors and thus are of special interest for the Earth sciences. Here, we report finding of the new phase, named disarag, which is dynamically disordered aragonite with freely rotating CO3 groups, similar to that in the CaCO3-V phase with a calcite-like structure. Disarag has a stability field expanding from 3 to 10 GPa and from 1600 to 2000 K. Consideration of twinned structure enlarges this field, decreasing the transition temperature from aragonite to disarag at 100-300 K. At P-T parameters corresponding to the transition from aragonite to disarag, the marked disappearance of the diffraction peaks is observed in in situ experiments. We show that, among known phases of CaCO3, disarag is the best candidate for the explanation of this reconstruction of diffraction pattern. Also, for the first time, using ab initio molecular dynamics technique, we determine equilibrium curves between calcite and its disordered phases CaCO3-IV and CaCO3-V. We show that the transitions of alkaline-earth carbonates CaCO3, SrCO3, and BaCO3 to the disordered states start when the critical angle of librations of the CO3 group about the axis perpendicular to the molecular three-fold axis exceeds 45 degrees. The calcite-like structure of CaCO3 is characterized by more intense librations than the aragonite-like structure of this compound and reaches the critical angle at lower temperatures. As a result, calcite transforms into the disordered state at lower temperatures than aragonite.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2020
National Category
Geochemistry
Identifiers
urn:nbn:se:kth:diva-300671 (URN)10.1021/acs.jpcc.0c08309 (DOI)000598118800040 ()2-s2.0-85097867913 (Scopus ID)
Note

QC 20210924

Available from: 2021-09-24 Created: 2021-09-24 Last updated: 2022-06-25Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-7531-3210

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