In order to study the performance of interatomic potentials and their reliability at higher pressures, the phase diagrams of two different embedded-atom-type potential models (EAMs) and a modified embedded-atom model (MEAM) of lithium are compared. The calculations were performed by using the nested sampling technique in the pressure range 0.01-20 GPa, in order to determine the liquid-vapor critical point, the melting curve, and the different stable solid phases of the compared models. The low-pressure stable structure below the melting line is found to be the body-centered-cubic (bcc) structure in all cases, but the higher pressure phases and the ground-state structures show a great variation, being face-centered cubic (fcc), hexagonal close-packed (hcp), a range of different close-packed stacking variants, and highly symmetric open structures are observed as well. A notable behavior of the EAM of Nichol and Ackland ( , , 184101) is observed, that the model displays a maximum temperature in the melting line, similarly to experimental results.
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http://dx.doi.org/10.1021/acs.jpcb.0c03882 | DOI Listing |
Inorg Chem
January 2025
Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States.
A recent article ( 2024, 146, 7506-7514) details a pressure-temperature (-) phase diagram for the Ruddlesden-Popper bilayer nickelate LaNiO (LNO-2222) using synchrotron X-ray diffraction. This study identifies a phase transition from (#63) to (#69) within the temperature range of 104-120 K under initial pressure and attributes the 4/ (#139) space group to the structure responsible for the superconductivity of LNO-2222. Herein, we examine the temperature-dependent structural evolution of LNO-2222 single crystals at ambient pressure.
View Article and Find Full Text PDFMacromolecules
December 2024
Department οf Physics, University οf Ioannina, Ioannina 45110, Greece.
We report the pressure-temperature (-) phase diagram, the origin of the subglass dynamics, and the crystallization kinetics of the biobased polyester poly(ethylene 2,5-furanoate) (PEF), through dielectric spectroscopy (DS) measurements performed as a function of temperature and pressure. The phase diagram comprises four different "phases"; glass, quenched melt, crystalline, and normal melt. The cold crystallization temperature, , increases linearly with pressure (according to the Clausius-Clapeyron equation) as / ∼ 240 K·GPa and is accompanied by a small change in specific volume (Δ = 0.
View Article and Find Full Text PDFJ Phys Chem Lett
January 2025
Materials Physics Center, CSIC-UPV/EHU, Paseo de Manuel Lardizabal, 5, 20018 Donostia - San Sebastian, Spain.
Hybrid perovskites exhibit complex structures and phase behavior under different thermodynamic conditions and chemical environments, the understanding of which continues to be pivotally important for tailoring their properties toward improved operational stability. To this end, we present for the first time a comprehensive neutron and synchrotron diffraction investigation over the pressure-temperature phase diagram of the paradigmatic hybrid organic-inorganic perovskite methylammonium lead iodide (MAPbI). This ambitious experimental campaign down to cryogenic temperatures and tens of kilobars was supported by extensive molecular dynamics simulations validated by the experimental data, to track the structural evolution of MAPbI under external physical stimuli at the atomic and molecular levels.
View Article and Find Full Text PDFProc Natl Acad Sci U S A
December 2024
Department of Earth and Planetary Science, University of California, Berkeley, CA 94720.
The Voyager spacecraft discovered that the ice giants Uranus and Neptune have nondipolar magnetic fields, defying expectations that a thick interior layer of planetary ices would generate strong dipolar fields. Stanley and Bloxham showed that nondipolar fields emerge if the magnetic field is only generated in a thin outer layer. However, the origin and composition of this dynamo active layer has so far remained elusive.
View Article and Find Full Text PDFNatl Sci Rev
December 2024
State Key Laboratory of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China.
Hydride superconductors continue to fascinate the communities of condensed matter physics and material scientists because they host the promising near room-temperature superconductivity. Current research has concentrated on the new hydride superconductors with the enhancement of the superconducting transition temperature ( ). The multiple extreme conditions (high pressure/temperature and magnetic field) will introduce new insights into hydride superconductors.
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