Related Experiment Video
Updated: Apr 16, 2026
06:37
Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package
Published on: September 17, 2021
5.3K
Diffusivity and short-time dynamics in two models of silica
Erik Lascaris1, Mahin Hemmati2, Sergey V Buldyrev3
1Center for Polymer Studies and Department of Physics, Boston University, Boston, Massachusetts 02215, USA.
The Journal of Chemical Physics
|March 16, 2015
Summary
The WAC silica model reveals that diffusivity indicates proximity to a liquid-liquid critical point (LLCP). Reduced pressure causes an abrupt transition from high- to low-density liquid states, explained by the Adam-Gibbs relation.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Computational Chemistry
Background:
- Silica models like BKS and WAC are used to study liquid dynamics.
- The WAC model is particularly relevant for studying liquid-liquid critical points (LLCPs).
Purpose of the Study:
- To investigate the dynamic behavior of silica using the BKS and WAC models.
- To explore the relationship between diffusivity and proximity to a LLCP in silica models.
Main Methods:
- Molecular dynamics simulations of silica models (BKS and WAC).
- Analysis of Si diffusivity as a function of pressure.
- Application of the Adam-Gibbs relation to interpret dynamic transitions.
Main Results:
- Diffusivity serves as a key indicator of a liquid's proximity to criticality.
- A significant 3-4 order of magnitude jump in Si diffusivity was observed upon pressure reduction.
- This abrupt transition from high- to low-density liquid states is consistent with the Adam-Gibbs relation.
Conclusions:
- The WAC silica model effectively captures dynamics near a liquid-liquid critical point.
- Diffusivity changes can signal transitions between liquid states.
- The Adam-Gibbs relation provides a framework for understanding these transitions and estimating configurational entropy.
Related Concept Videos
01:09Theories of Dissolution: The Danckwerts' Model and Interfacial Barrier Model
924
Various dissolution theories provide insight into the factors that influence the dissolution rate. Danckwerts' Model suggests that turbulence, rather than a stagnant layer, characterizes the dissolution medium at the solid-liquid interface. In this model, the agitated solvent contains macroscopic packets that move to the interface via eddy currents, facilitating the absorption and delivery of the drug to the bulk solution. The regular replenishment of solvent packets maintains the...
924
01:15Theories of Dissolution: Diffusion Layer Model
2.3K
Dissolution, the process by which drug particles dissolve in a solvent, is explained by the diffusion layer model, a theoretical framework that simulates the absorption of oral drugs and allows us to analyze experimental data.
This process starts with a thin layer, saturated with the drug, forming at the interface between the solid and liquid. The solute then diffuses from this layer into the main solution. The Noyes-Whitney equation suggests that the rate of dissolution relies on the diffusion...
This process starts with a thin layer, saturated with the drug, forming at the interface between the solid and liquid. The solute then diffuses from this layer into the main solution. The Noyes-Whitney equation suggests that the rate of dissolution relies on the diffusion...
2.3K
00:57Physiological Pharmacokinetic Models: Blood Flow-Limited Versus Diffusion-Limited Models
470
Physiological pharmacokinetic models, often called flow-limited or perfusion models, typically assume a swift drug distribution between tissue and venous blood, creating a rapid drug equilibrium. This premise is based on the idea that drug diffusion is extremely fast, and the cell membrane presents no barrier to drug permeation. In this scenario, where no drug binding occurs, the drug concentration in the tissue equals that of the venous blood leaving the tissue. This greatly simplifies the...
470
03:48Behavior of Gas Molecules: Molecular Diffusion, Mean Free Path, and Effusion
32.2K
Although gaseous molecules travel at tremendous speeds (hundreds of meters per second), they collide with other gaseous molecules and travel in many different directions before reaching the desired target. At room temperature, a gaseous molecule will experience billions of collisions per second. The mean free path is the average distance a molecule travels between collisions. The mean free path increases with decreasing pressure; in general, the mean free path for a gaseous molecule will be...
32.2K
01:17Passive Diffusion: Overview and Kinetics
1.9K
Passive diffusion is a critical process that allows small lipophilic drugs to cross the cell membrane along a concentration gradient. This mechanism's efficiency depends on four primary factors: the membrane's surface area, the drug's lipid-water partition coefficient, the concentration gradient, and the membrane's thickness.
When administered orally, drugs establish a substantial concentration gradient between the gastrointestinal (GI) lumen and the bloodstream, expediting...
When administered orally, drugs establish a substantial concentration gradient between the gastrointestinal (GI) lumen and the bloodstream, expediting...
1.9K
01:21Diffusion
7.4K
Diffusion is a type of passive transport. In passive transport, a substance tends to move from an area of high concentration to an area of low concentration until the concentration is equal across the space. For example, take the diffusion of substances through the air. When someone opens a perfume bottle in a room filled with people, the perfume is at its highest concentration in the bottle and is at its lowest at the edges of the room. The perfume vapor will diffuse, or spread away, from the...
7.4K