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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.
Öppna denna publikation i ny flik eller fönster >>A metadynamics study of the fcc-bcc phase transition in Xenon at high pressure and temperature
2015 (Engelska)Ingår i: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 107, s. 66-71, artikel-id 6523Artikel i tidskrift (Refereegranskat) 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.

Nyckelord
Buckingham potential, Dynamical stability, Metadynamics, Solid-solid phase transition
Nationell ämneskategori
Annan fysik
Identifikatorer
urn:nbn:se:kth:diva-170224 (URN)10.1016/j.commatsci.2015.04.055 (DOI)000356964900010 ()2-s2.0-84930945679 (Scopus ID)
Forskningsfinansiär
Vetenskapsrådet
Anmärkning

QC 20150630

Tillgänglig från: 2015-06-30 Skapad: 2015-06-29 Senast uppdaterad: 2019-09-20Bibliografiskt granskad
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.
Öppna denna publikation i ny flik eller fönster >>Synthesis of heavy hydrocarbons at the core-mantle boundary
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2015 (Engelska)Ingår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, artikel-id 18382Artikel i tidskrift (Refereegranskat) 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.

Ort, förlag, år, upplaga, sidor
Nature Publishing Group, 2015
Nationell ämneskategori
Mineral- och gruvteknik
Identifikatorer
urn:nbn:se:kth:diva-180487 (URN)10.1038/srep18382 (DOI)000366571400001 ()26675747 (PubMedID)2-s2.0-84950349897 (Scopus ID)
Anmärkning

QC 20160115

Tillgänglig från: 2016-01-15 Skapad: 2016-01-14 Senast uppdaterad: 2017-11-30Bibliografiskt granskad
Mancarella, F., Balatsky, A. V., Wallin, M. & Rosengren, A. (2013). Angular momentum blockade in nanoscale high-T-c superconducting grains. Superconductors Science and Technology, 26(12)
Öppna denna publikation i ny flik eller fönster >>Angular momentum blockade in nanoscale high-T-c superconducting grains
2013 (Engelska)Ingår i: Superconductors Science and Technology, ISSN 0953-2048, E-ISSN 1361-6668, Vol. 26, nr 12Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We discuss the angular momentum blockade in small d-wave superconducting grains in an external field. We find that abrupt changes in the angular momentum state of the condensate, angular momentum blockade, occur as a result of changes in the angular momentum of the condensate in an external magnetic field. The effect represents a direct analogy with the Coulomb blockade. We use the Ginzburg-Landau formalism to illustrate how a magnetic field induces a deviation from the d-wave symmetry which is described by a (d(x2-y2)+id(xy))-order parameter. We derive the behavior of the volume magnetic susceptibility as a function of the magnetic field, and corresponding magnetization jumps at critical values of the field that should be experimentally observable in superconducting grains.

Nyckelord
Angular momentum state, Critical value, External fields, External magnetic field, Ginzburg-Landau formalism, Magnetization jump, Order parameter, Superconducting grains
Nationell ämneskategori
Annan fysik
Identifikatorer
urn:nbn:se:kth:diva-138360 (URN)10.1088/0953-2048/26/12/125014 (DOI)000327447200017 ()2-s2.0-84888372894 (Scopus ID)
Forskningsfinansiär
Vetenskapsrådet, VR 621-2012-298 VR 621-2012-3984EU, Europeiska forskningsrådet
Anmärkning

QC 20140107

Tillgänglig från: 2014-01-07 Skapad: 2013-12-19 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
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
Öppna denna publikation i ny flik eller fönster >>Impact of crystal lattice defects on crystal melting: A molecular dynamics study
2013 (Engelska)Ingår i: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 79, s. 95-98Artikel i tidskrift (Refereegranskat) 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.

Nyckelord
Superheating, Overheating, Lennard-Jonesium, Melting
Nationell ämneskategori
Fysik
Identifikatorer
urn:nbn:se:kth:diva-132197 (URN)10.1016/j.commatsci.2013.06.026 (DOI)000324471100014 ()2-s2.0-84879937895 (Scopus ID)
Anmärkning

QC 20131024

Tillgänglig från: 2013-10-24 Skapad: 2013-10-24 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
Belonoshko, A. B., Lukinov, T., Burakovsky, L., Preston, D. L. & Rosengren, A. (2013). Melting of a polycrystalline material. The European Physical Journal Special Topics, 216(1), 199-204
Öppna denna publikation i ny flik eller fönster >>Melting of a polycrystalline material
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2013 (Engelska)Ingår i: The European Physical Journal Special Topics, ISSN 1951-6355, E-ISSN 1951-6401, Vol. 216, nr 1, s. 199-204Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Calculating the melting temperature of a solid with a known model of interaction between atoms is nowadays a comparatively simple task. However, when one simulates a single crystal by molecular dynamics method, it does not normally melt at the melting temperature. Instead, one has to significantly overheat it. Yet, a real material melts at the melting point. Here we investigate the impact of the defects and the grain boundaries on melting. We demonstrate that defects and grain boundaries have similar impact and make it possible to simulate melting in close vicinity of thermodynamic melting temperature. We also show that the Z method might be non-applicable in discriminating a stable submelting phase.

Nyckelord
Argon
Nationell ämneskategori
Fysik
Identifikatorer
urn:nbn:se:kth:diva-119060 (URN)10.1140/epjst/e2013-01743-1 (DOI)000314364300021 ()2-s2.0-84873507587 (Scopus ID)
Forskningsfinansiär
Vetenskapsrådet
Anmärkning

QC 20130306

Tillgänglig från: 2013-03-06 Skapad: 2013-03-05 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
Lundow, P. H. & Rosengren, A. (2013). The p,q-binomial distribution applied to the 5d Ising model. Philosophical Magazine, 93(14), 1755-1770
Öppna denna publikation i ny flik eller fönster >>The p,q-binomial distribution applied to the 5d Ising model
2013 (Engelska)Ingår i: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 93, nr 14, s. 1755-1770Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The leading order form of the magnetization distribution is well-known for the 5d Ising model close to . Its corrections-to-scaling are not known though. Since we have earlier established that this distribution is extremely well-fitted by a -binomial distribution, we report considerably longer series expansions for its moments in terms of three parameters, providing new details on the scaling behaviour of the Ising distribution and its moments near . As applications, we give for example the scaling formulas for the ratios , and the full distribution at .

Nyckelord
Ising model, magnetization distribution, q-binomial
Nationell ämneskategori
Den kondenserade materiens fysik
Identifikatorer
urn:nbn:se:kth:diva-124301 (URN)10.1080/14786435.2012.750770 (DOI)000319334800010 ()2-s2.0-84878728714 (Scopus ID)
Anmärkning

QC 20130701

Tillgänglig från: 2013-07-01 Skapad: 2013-06-28 Senast uppdaterad: 2020-05-11Bibliografiskt granskad
Belonoshko, A. B. & Rosengren, A. (2012). A possible mechanism of copper corrosion in anoxic water. Philosophical Magazine, 92(36), 4618-4627
Öppna denna publikation i ny flik eller fönster >>A possible mechanism of copper corrosion in anoxic water
2012 (Engelska)Ingår i: Philosophical Magazine, ISSN 1478-6435, E-ISSN 1478-6443, Vol. 92, nr 36, s. 4618-4627Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Recent experiments show that solid Cu reacts with anoxic water. The reaction is observed by measuring the hydrogen release. This release is continuous and stable over a period of months. We have since theoretically found that water adsorbs dissociatively at a copper surface. But this adsorption is not enough to explain the amount of hydrogen released in the experiment. This observation calls for the explanation of the removal of the reaction product from the surface to provide a clean Cu surface where the water dissociation takes place. In this paper we investigate, by first-principles calculations, two possible mechanisms for this removal: first the possibility of Cu-O-H nanoparticulate formation, and second the diffusion of the dissociation products into Cu. We show that while the formation of nanoparticulates is energetically unfavorable, the diffusion of OH along grain boundaries can be substantial. The OH being placed in a grain boundary of the Cu sample quickly dissociates and O and H atoms diffuse independently of each other. Such a diffusion is markedly larger than the diffusion in bulk Cu. Thus, grain boundary diffusion is a viable mechanism for providing a clean Cu surface for the dissociation of water at the Cu surface. An order-of-magnitude estimate of the amount of hydrogen released in this case agrees with experiment. But this mechanism is not enough to explain the result of the experiment. We propose the formation of nanocrystals of copper oxide as a second step. A decisive experiment is proposed. 

Nyckelord
ab initio, clusters, copper corrosion, diffusion, molecular dynamics, water
Nationell ämneskategori
Annan fysik
Identifikatorer
urn:nbn:se:kth:diva-116649 (URN)10.1080/14786435.2012.715251 (DOI)000313030900008 ()2-s2.0-84871292771 (Scopus ID)
Anmärkning

QC 20130124

Tillgänglig från: 2013-01-24 Skapad: 2013-01-22 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
Belonoshko, A. B. & Rosengren, A. (2012). High-pressure melting curve of platinum from ab initio Z method. Physical Review B. Condensed Matter and Materials Physics, 85(17), 174104
Öppna denna publikation i ny flik eller fönster >>High-pressure melting curve of platinum from ab initio Z method
2012 (Engelska)Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 85, nr 17, s. 174104-Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

Pt is widely used as a standard in high-pressure high-temperature experiments. The available experimental and theoretical data on Pt thermal stability is not consistent. We address the issue of high-pressure Pt melting by ab initio molecular dynamics. We demonstrate a remarkable consistency of our computed melting curve with the experimental data by N. R. Mitra, D. L. Decker, and H. B. Vanfleet [Phys. Rev. 161, 613 (1967)]. The extrapolation of their data, based on the Simon equation, nearly coincides with our ab initio computed melting curve. We propose the Pt melting curve in the form P-m(kbar) = 443.0[(T/T-m)(1.14) - 1].

Nyckelord
MOLECULAR-DYNAMICS SIMULATIONS, BRILLOUIN-ZONE INTEGRATIONS, TOTAL-ENERGY CALCULATIONS, AUGMENTED-WAVE METHOD, BASIS-SET, EQUATION, METALS, GRAPHITE, TEMPERATURE, STABILITY
Nationell ämneskategori
Den kondenserade materiens fysik
Identifikatorer
urn:nbn:se:kth:diva-96441 (URN)10.1103/PhysRevB.85.174104 (DOI)000303652700001 ()2-s2.0-84861163980 (Scopus ID)
Forskningsfinansiär
Vetenskapsrådet
Anmärkning
QC 20120605Tillgänglig från: 2012-06-05 Skapad: 2012-06-04 Senast uppdaterad: 2017-12-07Bibliografiskt granskad
Belonoshko, A., Koči, L. & Rosengren, A. (2012). Stability of the bcc phase of 4He close to the melting curve: A molecular dynamics study. Physical Review B. Condensed Matter and Materials Physics, 85(1), 012503
Öppna denna publikation i ny flik eller fönster >>Stability of the bcc phase of 4He close to the melting curve: A molecular dynamics study
2012 (Engelska)Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 85, nr 1, s. 012503-Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

We have investigated whether the Aziz et al. [J. Chem. Phys. 70, 4330 (1979)] model for (4)He renders the body-centered cubic phase more stable than the face-centered cubic phase in the proximity of the melting curve. Using molecular dynamics, we have simulated these solid phases in equilibrium with the liquid at a number of densities. In contrast to previous free energy molecular dynamics calculations, the model stabilizes the body-centered cubic phase. The stability field is just 5 degrees. wide below the melting curve at pressures around 140 Kbar and about 70 degrees wide at pressures around 750 Kbar. Considering that the body-centered cubic phase is dynamically unstable at low temperature, this result bears striking similarities to transition metal phase diagrams.

Nyckelord
CENTERED-CUBIC PHASE, EARTHS CORE, HELIUM, IRON, TRANSITIONS, DIAGRAM, EQUATION, STATE
Nationell ämneskategori
Den kondenserade materiens fysik
Identifikatorer
urn:nbn:se:kth:diva-61193 (URN)10.1103/PhysRevB.85.012503 (DOI)000299267200001 ()
Forskningsfinansiär
Vetenskapsrådet
Anmärkning
Updated from accepted to published. QC 20120403Tillgänglig från: 2012-01-16 Skapad: 2012-01-16 Senast uppdaterad: 2017-12-08Bibliografiskt granskad
Belonoshko, A., Arapan, S. & Rosengren, A. (2011). An ab initio molecular dynamics study of iron phases at high pressure and temperature. Journal of Physics: Condensed Matter, 23(48)
Öppna denna publikation i ny flik eller fönster >>An ab initio molecular dynamics study of iron phases at high pressure and temperature
2011 (Engelska)Ingår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 23, nr 48Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

The crystal structure of iron, the major component of the Earth's inner core (IC), is unknown for the IC high pressure (P; 3.3-3.6 Mbar) and temperature (T; 5000-7000 K). There is mounting evidence that the hexagonal close-packed (hcp) phase of iron, stable at the high P of the IC and a low T, might be unstable under the IC conditions due to the impact of high T and impurities. Experiments at the IC P and T are difficult and do not provide a conclusive answer as regards the iron stability at the pressure of the IC and temperatures close to the iron melting curve. Recent theory provides contradictory results regarding the nature of the stable Fe phase. We investigated the possibility of body-centered cubic (bcc) phase stabilization at the P and T in the vicinity of the Fe melting curve by using ab initio molecular dynamics. Thermodynamic calculations, relying on the model of uncorrelated harmonic oscillators, provide nearly identical free energies within the error bars of our calculations. However, direct simulation of iron crystallization demonstrates that liquid iron freezes in the bcc structure at the P of the IC and T = 6000 K. All attempts to grow the hcp phase from the liquid failed. The mechanism of bcc stabilization is explained. This resolves most of the earlier confusion.

Nationell ämneskategori
Den kondenserade materiens fysik
Identifikatorer
urn:nbn:se:kth:diva-61191 (URN)10.1088/0953-8984/23/48/485402 (DOI)000298141600016 ()2-s2.0-82455209440 (Scopus ID)
Forskningsfinansiär
Vetenskapsrådet
Anmärkning
QC 20120116Tillgänglig från: 2012-01-16 Skapad: 2012-01-16 Senast uppdaterad: 2017-12-08Bibliografiskt granskad
Organisationer
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0002-2076-5911

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