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SOLID DIFFUSION

WHAT IS IT?

Solid Diffusion in TerraMe

This model describes how diffusion occurs between two adjacent solids at it is based on NetLogo Solid Diffusion model http://ccl.northwestern.edu/netlogo/models/SolidDiffusion.

Solid diffusion is material transport by atomic motion, this phenomena is exhaustively studied in fields as materials science, physics, biology, geology, engineering and chemistry.

The main mechanisms for diffusion in solids are:

In this model we demonstrate that the Vacancy Diffusion Mechanism is caused by missing atoms in the metal crystal (Vacancies). These vacancies are occupied by atoms that move from areas of high concentration of “Atom of type B” (Figure 1) to areas with low concentration, until the concentration is equal throughtout the sample. 

                                               Figure 1. Material transport by atomic motion.

HOW IT WORKS

We define an initial state with two types of atoms, “Atoms of type A (green color)” and “Atoms of type B (blue color)”. In the initial state all green atoms are on the left and the blue atoms are on the right side. The vacancies (black color) are assigned to columns between the two materials, Figure 2.

As atoms move into vacancies, the vacancies disperse. In this model for simplification purposes, we assume that the materials have no vacancies in the beginning, and that all the vacancies start off in between the two materials. 

                                           Figure 2. Initial state with two types of atoms.

HOW TO USE IT

Parameters: 

                                     Figure 3. Simulation for two-dimensional diffusion between two solids.

THINGS TO NOTICE

This model is based on Vacancy Diffusion Mechanism, therefore the number of Atoms A and B, as the number of vacancies remains constant over the time. Materials have no vacancies at the beginning.

The model assume equal heat distribution through the metals.

Every particle has a random probability to move.

THINGS TO TRY

Some things to try with the model are:

EXTENDING THE MODEL

The model can be extended by considering other physical and chemical properties as:

TerraME FEATURES

This model used cellular space, observer, timer and legend.

More information on this model can be found at:

CREDITS AND REFERENCES