Related Experiment Video
Updated: Jun 3, 2026
11:03
An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Computing the viscosity of supercooled liquids: Markov Network model
Ju Li1, Akihiro Kushima, Jacob Eapen
1Department of Materials Science and Engineering, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America.
Plos One
|April 6, 2011
Summary
This study models the glass transition in supercooled liquids using a Markovian Network model. It reveals that a temperature-dependent energy landscape explains the dramatic viscosity changes observed during vitrification.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Computational Chemistry
Background:
- The glass transition, a phenomenon where liquid viscosity increases dramatically, lacks a clear first-principles explanation.
- Understanding the microscopic origins of this transition is crucial for materials science and condensed matter physics.
Purpose of the Study:
- To develop and implement a Markovian Network model for calculating shear viscosity in supercooled liquids.
- To elucidate the microscopic factors governing the glass transition by analyzing the atomistic energy landscape.
Main Methods:
- Numerical sampling of an atomistic energy landscape using a metadynamics-based algorithm.
- Calculation of shear stress relaxation via a master-equation description of hopping among local energy minima.
- Development of a Markovian Network model to simulate transition-state pathway trajectories.
Main Results:
- Established a quantitative link between temperature-dependent viscosity and the underlying potential energy and stress landscape.
- Demonstrated that different landscape topographies are required for high- and low-temperature viscosity regimes.
- Observed a crossover from Arrhenius to super-Arrhenius (fragile) behavior in viscosity for a binary liquid model.
Conclusions:
- A temperature-dependent energy landscape "terrain" is sufficient to explain the signature behavior of vitrification.
- Quantified the concept of a temperature-dependent effective activation barrier.
- Provided insights into the fundamental origin of the viscosity crossover observed in atomic dynamics during the glass transition.
Related Concept Videos
01:19Viscosity of Fluid
Viscosity measures the resistance a fluid offers to flow and deformation. It results from internal friction between layers of fluid moving relative to one another. Dynamic viscosity, denoted by the Greek letter mu (μ), quantifies the force needed to move one fluid layer over another. For Newtonian fluids like water and air, the relationship between the shearing stress and the rate of shearing strain is linear, meaning their viscosity remains constant regardless of the applied stress.
01:34Fluid Mosaic Model
The fluid mosaic model was first proposed as a visual representation of research observations. The model comprises the composition and dynamics of membranes and serves as a foundation for future membrane-related studies. The model depicts the structure of the plasma membrane with a variety of components, which include phospholipids, proteins, and carbohydrates. These integral molecules are loosely bound, defining the cell’s border and providing fluidity for optimal function.LipidsThe most...
01:19Fluid Mosaic Model
Scientists identified the plasma membrane in the 1890s and its principal chemical components (lipids and proteins) by 1915. The model for plasma membrane structure, proposed in 1935 by Hugh Davson and James Danielli, was the first model to be widely accepted in the scientific community. The model was based on the plasma membrane's "railroad track" appearance in early electron micrographs. Davson and Danielli theorized that the plasma membrane's structure resembled a sandwich with the analogy of...
02:39Phase Transitions: Vaporization and Condensation
The physical form of a substance changes on changing its temperature. For example, raising the temperature of a liquid causes the liquid to vaporize (convert into vapor). The process is called vaporization—a surface phenomenon. Vaporization occurs when the thermal motion of the molecules overcome the intermolecular forces, and the molecules (at the surface) escape into the gaseous state. When a liquid vaporizes in a closed container, gas molecules cannot escape. As these gas phase molecules...
02:39Phase Transitions: Melting and Freezing
Heating a crystalline solid increases the average energy of its atoms, molecules, or ions, and the solid gets hotter. At some point, the added energy becomes large enough to partially overcome the forces holding the molecules or ions of the solid in their fixed positions, and the solid begins the process of transitioning to the liquid state or melting. At this point, the temperature of the solid stops rising, despite the continual input of heat, and it remains constant until all of the solid is...
02:57Surface Tension, Capillary Action, and Viscosity
Surface Tension
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...