Difusional

Difusional is an adjective relating to diffusion, the net movement of particles from regions of higher concentration to regions of lower concentration as a result of random thermal motion. In scientific contexts it describes transport processes driven primarily by concentration gradients rather than bulk flow or applied forces. Diffusional transport can occur in gases, liquids, and solids and is often described statistically by diffusion coefficients.

The fundamental description uses Fick's laws. Fick's first law states that the diffusive flux J is proportional to the negative gradient of concentration: J = -D ∇C, where D is the diffusion coefficient. Fick's second law, ∂C/∂t = D ∇^2 C (for isotropic media), governs how concentration changes in time due to diffusion. Diffusion coefficients depend on temperature, medium, and the diffusing species and can differ for self-diffusion, where molecules move within a pure substance, and mutual diffusion, where different species diffuse relative to each other.

In solids, difusional processes can be slow and are often anisotropic in crystalline materials, with pathways controlled by lattice defects, grain boundaries, or porosity. In liquids and gases, diffusion typically occurs more rapidly.

Applications span material science, chemistry, geology, and biology. Examples include diffusion of solutes in polymers, gas diffusion through membranes, nutrient transport in tissues, and diffusion-controlled reaction kinetics. Measurements commonly use tracer diffusion experiments, concentration profiling, and nuclear magnetic resonance techniques to determine diffusion coefficients and mechanisms.