The optical properties of non-spherical particles have been studied for decades and there are a number of solution techniques to model distinct geometries. Of these methods, the Discrete Dipole Approximation (DDA) is known to compute electromagnetic scattering from irregularly shaped, heterogeneous particles. DDSCAT, which is the numerical implementation of DDA, is identified as a potential solver for electrically charged particles; however, there is a set of limitations and shortcomings to be addressed. The main concern is the conductivity, which introduces an infinitesimally thin charged monolayer on the particle surface. The side effect of this concept is a steep increase of refractive index and impedance. The DDSCAT can have trouble converging to a solution when the thin shell at the particle surface produces large losses due to having electromagnetic properties significantly different from the media on either side of the particle interface.

In this paper we introduce a method to calculate the optical response of charged particles at wavelengths where charge-induced resonances typically occur. The method takes advantage of the interfaces to DDSCAT, while the conductive shell is simulated by a multi-level material distribution. The discretization involves both the 3D model of the particle and the charge distribution. The latter is determined numerically by solving the Laplace equation. The surface- and volume-averaging parameter is used to avoid large refractive indices, but the results are still accurate within a few percent. The method is validated for sensitivity and specificity in modeling optical resonances that are analytically retrievable for ideal spheres. The applicability to an irregularly shaped particle is demonstrated consequently. Implementation algorithms and numerical solvers are made publicly available, which allows light-scattering modelers to study particles in different media under different conditions.

对非球形粒子的光学特性已经进行了数十年的研究，并且有许多解决方案技术可以对不同的几何形状进行建模。在这些方法中，已知离散偶极近似（DDA）用于从形状不规则的异质粒子计算电磁散射。DDSCAT是DDA的数字实现，被确定为带电粒子的电势求解器。但是，存在一系列要解决的局限和缺点。主要关注的是电导率，它在粒子表面引入了无限薄的带电单层。这个概念的副作用是折射率和阻抗的急剧增加。

在本文中，我们介绍了一种计算带电粒子在通常发生电荷感应共振的波长处的光学响应的​​方法。该方法利用了与DDSCAT的接口，同时通过多层材料分布来模拟导电外壳。离散化涉及粒子的3D模型和电荷分布。后者是通过求解拉普拉斯方程数值确定的。表面和体积平均参数用于避免较大的折射率，但是结果仍在百分之几以内。该方法在对光学共振进行建模的敏感性和特异性方面经过验证，该光学共振可通过分析检索出理想球体。因此证明了对不规则形状的颗粒的适用性。