Commercial software such as COMSOL Multiphysics® uses the bulk
conductivity of a material as an approximation for metallic response when using the RF package. It is important to consider the boundaries set by this assumption as we simulate a wide range of devices and materials for opticalto-microwave regimes. We separated the bound and free charges previously; however, we never looked at their resultant combination in metamaterials. Making a slight notation change when compared to Eq. (2.13), and introducing a dimensionless weighting factor fi, the free electron or conduction electron effects are summarized using the Drude model.
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