Review of Charge Relaxation
Starting from the Charge Relaxation Theory, it is crucial to consider two distinct time scales when modeling charge dynamics. These time scales are:
1
The intrinsic charge relaxation time τ, which is a characteristic time scale for the redistribution of charges within a material.
2
The external time scale t, which corresponds to the duration over which a device is energized or the observation period.
By comparing these two time scales, we can define the behavior of materials as follows:
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Insulator: if τ >> t, charges do not have sufficient time to redistribute significantly. This scenario is typically modeled using the Electrostatics interface, where Poisson’s equation is solved.
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Conductor: τ << t, charges have ample time to redistribute. This is usually modeled using the Electric Currents interface, which solves the current conservation equation.
In more complex cases where charge dynamics cannot be easily prescribed, a separate charge transport formulation is required. Various specialized modules are available for different types of problems:
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The Plasma Module focuses on modeling low-pressure plasma reactors in gases.
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The Electrochemistry Module is designed for modeling interactions between chemical and electrical energy in liquid electrolytes.
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The Semiconductor Module is primarily used for modeling crystalline solids based on band-gap theory.
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The Electric Discharge Module addresses modeling electric discharges and breakdowns in gases, liquids, and solids.
These add-on products offer tailored solutions for specific charge transport challenges across different environments.