mnpbem-material 0.1.4

Material dielectric models for plasmonic electrodynamics in MNPBEM-Python.

mnpbem-material

mnpbem-material implements dielectric-function models used in plasmonic electrodynamics. The module provides analytical material models and tabulated optical constants for metals such as Au, Ag, and Al.

Features

• Constant dielectric model for homogeneous media.
• Drude dielectric model for free-electron metals.
• Tabulated (E, n, k) optical constants with wavelength-domain interpolation.
• Ready-to-use datasets for common plasmonic materials.

Implemented Formulations

1. Constant Dielectric Function

For wavelength-independent permittivity:

$$ \varepsilon(\lambda) = \varepsilon_0 $$

The wave number is:

$$ k(\lambda) = \frac{2\pi}{\lambda}\sqrt{\varepsilon} $$

where:

• $\varepsilon_0$ is the constant dielectric permittivity.
• $\lambda$ is the wavelength.

2. Drude Model

For free-electron metal response:

$$ \varepsilon(\omega) = \varepsilon_\infty - \frac{\omega_p^2}{\omega(\omega + i\gamma)} $$

where:

• $\varepsilon_\infty$ is the high-frequency dielectric constant.
• $\omega_p$ is the plasma frequency.
• $\gamma$ is the damping constant.
• $\omega$ is the angular frequency.

Energy-wavelength conversion used in the implementation (using the physical constant in eV*nm units):

$$ \omega_{\mathrm{eV}} = \frac{C_{\mathrm{eV\cdot nm}}}{\lambda_{\mathrm{nm}}}, \qquad C_{\mathrm{eV\cdot nm}} \approx 1239.841984 $$

Material parameters for Au, Ag, and Al are aligned with the established MNPBEM Drude-style parameterization.

3. Tabulated Material Model

Given tabulated optical constants $(E, n, k)$, the dielectric function is:

$$ \varepsilon = (n + i k)^2 $$

Interpolation is performed in the wavelength domain after converting tabulated energy values.

Implementation

• Core implementation: src/mnpbem_material/models.py
• Material datasets: src/mnpbem_material/data/*.dat

Dependencies

Runtime dependencies are installed automatically by pip:

• numpy>=1.24

Installation

pip install mnpbem-material

Example Usage

Runnable example:

• examples/basic_usage.py

Run:

python examples/basic_usage.py

Author

• GALIH RIDHO UTOMO
• [e-mail]