95 research outputs found
Minimal quantum viscosity from fundamental physical constants
Viscosity of fluids is strongly system-dependent, varies across many orders
of magnitude and depends on molecular interactions and structure in a complex
way not amenable to first-principles theories. Despite the variations and
theoretical difficulties, we find a new quantity setting the minimal kinematic
viscosity of fluids: , where
and are electron and molecule masses. We subsequently introduce a new
property, the "elementary" viscosity with the lower bound set by
fundamental physical constants and notably involving the proton-to-electron
mass ratio:
, where
is the proton mass. We discuss the connection of our result to the bound
found by Kovtun, Son and Starinets in strongly-interacting field theories
Emergence and Evolution of the k Gap in Spectra of Liquid and Supercritical States
This research utilized Queen Mary’s MidPlus computational
facilities, supported by QMUL Research-IT and
funded by EPSRC Grant No. EP/K000128/1. We are grateful
to the Royal Society, the China Scholarship Council, and
V. V. B. to the RSF (for Grant No. 14-22-00093)
Solid-state diffusion in amorphous zirconolite
his research utilised Queen Mary's MidPlus computational facilities, supported by QMUL Research-IT and funded by EPSRC grant EP/K000128/1. We are grateful to E. Maddrell for discussions and to CSC for support
Dynamic transition in supercritical iron
Y. F. thanks the Russian Scientific Center at Kurchatov Institute and Joint Supercomputing Center of Russian Academy of Science for computational facilities. The work was supported in part by the Russian Science Foundation (Grant No 14-22-00093). Y. F. is grateful to the Ministry of Education and Science of Russian Federation (project MK-2099.2013.2) and to the grant of the Government of the Russian Federation 14.A12.31.0003 for the support
Universal interrelation between dynamics and thermodynamics and a dynamically driven “c” transition in fluids
Our very wide survey of the supercritical phase diagram and its key properties reveals a universal interrelation between dynamics and thermodynamics and an unambiguous transition between liquidlike and gaslike states. This is seen in the master plot showing a collapse of the data representing the dependence of specific heat on key dynamical parameters in the system for many different paths on the phase diagram. As a result, the observed transition is path independent. We call it a “c” transition due to the c-shaped curve parametrizing the dependence of the specific heat on key dynamical parameters. The c transition has a fixed inversion point and provides a new structure to the phase diagram, operating deep in the supercritical state (up to, at least, 2000 times the critical pressure and 50 times the critical temperature). The data collapse and path independence as well as the existence of a special inversion point on the phase diagram are indicative of either of a sharp crossover or a new phase transition in the deeply supercritical state
Direct Experimental Evidence of Longitudinal and Transverse Mode Hybridization and Anticrossing in Simple Model Fluids
Generic mechanism for generating a liquid-liquid phase transition
Recent experimental results indicate that phosphorus, a single-component
system, can have two liquid phases: a high-density liquid (HDL) and a
low-density liquid (LDL) phase. A first-order transition between two liquids of
different densities is consistent with experimental data for a variety of
materials, including single-component systems such as water, silica and carbon.
Molecular dynamics simulations of very specific models for supercooled water,
liquid carbon and supercooled silica, predict a LDL-HDL critical point, but a
coherent and general interpretation of the LDL-HDL transition is lacking. Here
we show that the presence of a LDL and a HDL can be directly related to an
interaction potential with an attractive part and two characteristic
short-range repulsive distances. This kind of interaction is common to other
single-component materials in the liquid state (in particular liquid metals),
and such potentials are often used to decribe systems that exhibit a density
anomaly. However, our results show that the LDL and HDL phases can occur in
systems with no density anomaly. Our results therefore present an experimental
challenge to uncover a liquid-liquid transition in systems like liquid metals,
regardless of the presence of the density anomaly.Comment: 5 pages, 3 ps Fig
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