Related Experiment Video
Updated: Jan 17, 2026
06:37
Analyzing Melts and Fluids from Ab Initio Molecular Dynamics Simulations with the UMD Package
Published on: September 17, 2021
5.0K
Dynamic correlations in a polar fluid: Confronting stochastic density functional theory to simulations.
Sleeba Varghese1, Pierre Illien1, Benjamin Rotenberg1,2
1Sorbonne Université, CNRS, Laboratoire PHENIX (Physicochimie des Electrolytes et Nanosystèmes Interfaciaux), 4 Place Jussieu, 75005 Paris, France.
The Journal of Chemical Physics
|September 22, 2025
Summary
We developed a stochastic density functional theory (SDFT) to model polar fluid dynamics. Modified SDFT accurately predicts polarization fluctuations in Stockmayer fluids, crucial for electrolytes and biological systems.
Area of Science:
- Physics
- Physical Chemistry
- Computational Science
Background:
- Polar fluids like electrolytes and biological media require accurate dynamic behavior models.
- The Stockmayer fluid, a model for dipolar liquids, is key to understanding these dynamics.
Purpose of the Study:
- To develop and apply a stochastic density functional theory (SDFT) framework for polarization dynamics in Stockmayer fluids.
- To analyze longitudinal and transverse polarization field components using linearized SDFT.
- To compare SDFT predictions with Brownian Dynamics simulations.
Main Methods:
- Derivation of analytical expressions for intermediate scattering functions and dynamic structure factors from Langevin dynamics.
- Application of linearized stochastic density functional theory (SDFT).
- Comparison with Brownian Dynamics simulations and incorporation of the Kirkwood factor.
Main Results:
- Linearized SDFT accurately describes longitudinal polarization fluctuations.
- Transverse fluctuations were initially underestimated due to neglected dipolar correlations.
- Modified SDFT incorporating the Kirkwood factor achieved quantitative agreement for both components.
Conclusions:
- SDFT provides a valuable coarse-grained model for polar fluid dynamics.
- Collective effects significantly influence polarization relaxation in dipolar liquids.
- The modified SDFT framework offers improved accuracy for modeling complex polar systems.
Related Concept Videos
01:15Dimensionless Groups in Fluid Mechanics
762
Dimensionless groups in fluid mechanics provide simplified ratios that help analyze fluid behavior without relying on specific units. The Reynolds number (Re), which represents the ratio of inertial to viscous forces, distinguishes between laminar and turbulent flows, making it essential in the design of pipelines and aerodynamic surfaces. The Froude number (Fr), the ratio of inertial to gravitational forces, is particularly useful in predicting wave formation and hydraulic jumps in...
762
01:18Newtonian Fluid: Problem Solving
885
Newtonian fluids exhibit a constant viscosity, meaning their shear stress and shear strain rate are directly proportional. This property ensures a predictable and stable response to applied forces, maintaining a linear relationship between force and flow. Examples include water, air, and light oils, consistently demonstrating this proportional behavior regardless of external conditions.
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
A velocity gradient forms within the fluid when a Newtonian fluid is placed between two parallel plates, with...
885
01:29Potential Due to a Polarized Object
726
A neutral atom consists of a positively charged nucleus surrounded by a negatively charged electron cloud. When placed in an external electric field, the external electric force pulls the electrons and nucleus apart, opposite to the intrinsic attraction between the nucleus and the electrons. The opposing forces balance each other with a slight shift between the center of masses of the nucleus and the electron cloud, resulting in a polarized atom. On the other hand, a few molecules, like water,...
726
01:11Pressure Variation in a Fluid at Rest
739
In a fluid at rest, the pressure at any point beneath the fluid surface depends solely on the depth, not on the container's shape or size. This principle, known as hydrostatic pressure, arises because, in stationary fluids, there is no acceleration, meaning the forces within the fluid balance out. Only vertical forces, caused by the weight of the fluid above, contribute to pressure changes with depth.
When measuring pressure at two different levels within the fluid, the difference in...
When measuring pressure at two different levels within the fluid, the difference in...
739
01:17Accelerating Fluids
2.2K
When a fluid is in constant acceleration, the pressure and buoyant force equations are modified. Suppose a beaker is placed in an elevator accelerating upward with a constant acceleration, a. In the beaker, assume there is a thin cylinder of height h with an infinitesimal cross-sectional area, ΔS.
The motion of the liquid within this infinitesimal cylinder is considered to obtain the pressure difference. Three vertical forces act on this liquid:
The motion of the liquid within this infinitesimal cylinder is considered to obtain the pressure difference. Three vertical forces act on this liquid:
2.2K
01:19Viscosity of Fluid
1.2K
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.
1.2K