903 research outputs found
Percolation line of stable clusters in supercritical fluids
We predict that self-bound clusters of particles exist in the supercritical
phase of simple fluids. These clusters, whose internal temperature is lower
than the global temperature of the system, define a percolation line that
starts at the critical point. This line should be physically observable.
Possible experiments showing the validity of these predictions are discussed.Comment: 5 pages, 3 figures, corrected some typo
Analyzing Fragmentation of Simple Fluids with Percolation Theory
We show that the size distributions of fragments created by high energy
nuclear collisions are remarkably well reproduced within the framework of a
parameter free percolation model. We discuss two possible scenarios to explain
this agreement and suggest that percolation could be an universal mechanism to
explain the fragmentation of simple fluids.Comment: 12 pages, 11 figure
Partial energies fluctuations and negative heat capacities
We proceed to a critical examination of the method used in nuclear
fragmentation to exhibit signals of negative heat capacity. We show that this
method leads to unsatisfactory results when applied to a simple and well
controlled model. Discrepancies are due to incomplete evaluation of potential
energies.Comment: Modified figures 3 and
A model for liquid-striped liquid phase separation in liquids of anisotropic polarons
The phase separation between a striped polaron liquid at the particular
density and a high density polaron liquid is described by a modified Van der
Waals scheme. The striped polaron liquid represents the pseudo gap matter or
Wigner-like polaron phase at 1/8 doping in cuprate superconductors. The model
includes the tendency of pseudo- Jahn-Teller polarons to form anisotropic
directional bonds at a preferential volume with the formation of different
liquid phases. The model gives the coexistence of a first low density polaron
striped liquid and a second high density liquid that appears in cuprate
superconductors for doping larger than 1/8. We discuss how the strength of
anisotropic bonds controls the variation the phase separation scenarios for
complex systems in the presence of a quantum critical point where the phase
separation vanishes.Comment: 10 pages, 3 figure
Experimental Signals of Phase Transition
The connection between the thermodynamics of charged finite nuclear systems
and the asymptotically measured partitions is presented. Some open questions,
concerning in particular equilibrium partitions are discussed. We show a
detailed comparison of the decay patterns in Au+ C,Cu,Au central collisions and
in Au quasi-projectile events. Observation of abnormally large fluctuations in
carefully selected samples of data is reported as an indication of a first
order phase transition (negative heat capacity) in the nuclear equation of
state.Comment: 8 pages, 8th International Conference on Nucleus-Nucleus Collisions,
Moscow 200
A Little Big Bang scenario of fragmentation
We suggest a multifragmentation scenario in which fragments are produced at an early, high temperature and high density, stage of the reaction. In this scenario, self-bound clusters of particles in the hot and dense fluid are the precursors of the observed fragments. This solves a number of recurrent problems concerning the kinetic energies and the temperature of the fragments, encountered with the standard low density fragmentation picture. The possibility to recover the initial thermodynamic parameters from the inspection of the asymptotic fragment size and kinetic energy distributions is discussed
Expansion of the Materials Cloud 2D Database
Two-dimensional (2D) materials are among the most promising candidates for beyond-silicon electronic, optoelectronic, and quantum computing applications. Recently, their recognized importance sparked a push to discover and characterize novel 2D materials. Within a few years, the number of experimentally exfoliated or synthesized 2D materials went from a few to more than a hundred, with the number of theoretically predicted compounds reaching a few thousand. In 2018 we first contributed to this effort with the identification of 1825 compounds that are either easily (1036) or potentially (789) exfoliable from experimentally known 3D compounds. Here, we report on a major expansion of this 2D portfolio thanks to the extension of the screening protocol to an additional experimental database (MPDS) as well as the updated versions of the two databases (ICSD and COD) used in our previous work. This expansion leads to the discovery of an additional 1252 monolayers, bringing the total to 3077 compounds and, notably, almost doubling the number of easily exfoliable materials to 2004. We optimize the structural properties of all these monolayers and explore their electronic structure with a particular emphasis on those rare large-bandgap 2D materials that could be precious in isolating 2D field-effect-transistor channels. Finally, for each material containing up to 6 atoms per unit cell, we identify the best candidates to form commensurate heterostructures, balancing requirements on supercell size and minimal strain
A "Little Big Bang" Scenario of Multifragmentation
We suggest a multifragmentation scenario in which fragments are produced at
an early, high temperature and high density, stage of the reaction. In this
scenario, self-bound clusters of particles in the hot and dense fluid are the
precursors of the observed fragments. This solves a number of recurrent
problems concerning the kinetic energies and the temperature of the fragments,
encountered with the standard low density fragmentation picture. The
possibility to recover the initial thermodynamic parameters from the inspection
of the asymptotic fragment size and kinetic energy distributions is discussed.Comment: 15 pages, 12 figure
Nanoscale phase separation in the iron chalcogenide superconductor K0.8Fe1.6Se2 as seen via scanning nanofocused x-ray diffraction
Advanced synchrotron radiation focusing down to a size of 300 nm has been
used to visualize nanoscale phase separation in the K0.8Fe1.6Se2
superconducting system using scanning nanofocus single-crystal X-ray
diffraction. The results show an intrinsic phase separation in K0.8Fe1.6Se2
single crystals at T< 520 K, revealing coexistence of i) a magnetic phase
characterized by an expanded lattice with superstructures due to Fe vacancy
ordering and ii) a non-magnetic phase with an in-plane compressed lattice. The
spatial distribution of the two phases at 300 K shows a frustrated or arrested
nature of the phase separation. The space-resolved imaging of the phase
separation permitted us to provide a direct evidence of nanophase domains
smaller than 300 nm and different micrometer-sized regions with percolating
magnetic or nonmagnetic domains forming a multiscale complex network of the two
phases.Comment: 5 pages, 4 figure
Direct observation of nanoscale interface phase in the superconducting chalcogenide KFeSe with intrinsic phase separation
We have used scanning micro x-ray diffraction to characterize different
phases in superconducting KFeSe as a function of temperature,
unveiling the thermal evolution across the superconducting transition
temperature (T32 K), phase separation temperature (T520 K)
and iron-vacancy order temperature (T580 K). In addition to the
iron-vacancy ordered tetragonal magnetic phase and orthorhombic metallic
minority filamentary phase, we have found a clear evidence of the interface
phase with tetragonal symmetry. The metallic phase is surrounded by this
interface phase below 300 K, and is embedded in the insulating texture.
The spatial distribution of coexisting phases as a function of temperature
provides a clear evidence of the formation of protected metallic percolative
paths in the majority texture with large magnetic moment, required for the
electronic coherence for the superconductivity. Furthermore, a clear
reorganization of iron-vacancy order around the T and T is found
with the interface phase being mostly associated with a different iron-vacancy
configuration, that may be important for protecting the percolative
superconductivity in KFeSe.Comment: 6 pages, 4 figure
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