Model system used to illustrate phase transition of a mixture of active and passive particles
Systems containing self-propelling particles, such as bacteria or artificial colloidal particles, are always out of equilibrium but may show interesting transitions between different states, reminiscent of phase transitions in Systems containing self-propelling particles, such as bacteria or artificial colloidal particles, are always out of equilibrium but may show interesting transitions between different states, reminiscent of phase transitions in equilibrium.
Snapshots from a molecular dynamics simulation with 547 colloids and 1,781 polymers in an elongated simulation box. The upper image shows an equilibrium configuration of the passive system which did not phase-separate. The lower image is the corresponding active system in its steady state which is clearly phase-separated. In both pictures, colloids are shown in yellow and polymers in black. (ill./©: Peter Virnau, JGU)
However, application of analytical and computational methodologies from equilibrium statistical mechanics is questionable to study properties of such active systems. An international team of researchers – including Dr. Peter Virnau and Professor Kurt Binder of Johannes Gutenberg University Mainz (JGU), Benjamin Trefz of the JGU Graduate School of Excellence "Materials Science in Mainz" (MAINZ), and scientists from India and the U.S. – has studied the phase separation of a mixture of active and passive particles via molecular dynamics simulations and integral equation theoretical calculations. The distinctive feature of the model used is that the "activity" of the particles is tunable, containing passive particles as a limiting case for which already phase separation occurs.
"Our research results demonstrate that the introduction of activity may not only hamper phase separation as shown previously, but can enhance it as well, based on the coordination among the active particles," explained Dr. Peter Virnau of the Institute of Physics at Mainz University. Moreover, the researchers provided an approximate mapping of the phase behavior and structural properties of this nonequilibrium problem onto an equilibrium problem. A general validity of this mapping is subject to further careful testing. The confirmation of such validity would be an important step forward in understanding properties of active matter.
Subir K. Das et al.
Phase Behavior of Active Swimmers in Depletants: Molecular Dynamics and Integral Equation Theory
Physical Review Letters, 15 May 2014
Dr. Peter Virnau
Condensed Matter Theory Group (KOMET)
Institute of Physics
Johannes Gutenberg University Mainz (JGU)
D 55099 Mainz, GERMANY
phone +49 6131 39-20493
fax +49 6131 39-20496
Petra Giegerich | idw - Informationsdienst Wissenschaft
Further Improvement of Qubit Lifetime for Quantum Computers
09.12.2016 | Forschungszentrum Jülich
Electron highway inside crystal
09.12.2016 | Julius-Maximilians-Universität Würzburg
Physicists of the University of Würzburg have made an astonishing discovery in a specific type of topological insulators. The effect is due to the structure of the materials used. The researchers have now published their work in the journal Science.
Topological insulators are currently the hot topic in physics according to the newspaper Neue Zürcher Zeitung. Only a few weeks ago, their importance was...
In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.
Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...
Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...
A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.
Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...
In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.
“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...
16.11.2016 | Event News
01.11.2016 | Event News
14.10.2016 | Event News
09.12.2016 | Life Sciences
09.12.2016 | Ecology, The Environment and Conservation
09.12.2016 | Health and Medicine