Soft Matter II, PB
editDiffusion
editParticle flux
editConcentration gradients cause fluxes
editDiffusion from a point source
editRMS displacements
editMicroscopic dynamics of single particles
editBrownian motion
edit- Brownian motion
- A single diffusing particle can be modelled by a 3D random walk model
Comparison of random walk with bulk diffusion
edit- Particles flow from higher to lower concentrations only because of probabilities
- Distance travelled depends on √t rather than just t because of this stochastic nature
- Particles ultimately move in the direction that has fewer collisions
Microscopic expressions for the diffusion constant, D
editFriction in fluids
editEffect of shape on friction coefficients
editEinstein-Smoluchowski equation
editDiffusion constants
editCharacteristic time for diffusion
editDiffusion on macroscopic scales is very slow
editDynamic light scattering
editFormation of a speckle pattern
editTwinkling
editInstrumentation
editIntensity autocorrelation function
edit- The IACF is quite complicated
- It compares scattered light or X-ray intensity at time t with that at time t + τ
- If τ is short enough, the two intensities will be correlated (i.e. similar)
- The normalised IACF is