离散偶极近似代码DDSCAT 7.2用户指南
User Guide for the Discrete Dipole Approximation Code DDSCAT 7.2
摘要：
DDSCAT 7.2是一个可免费获得的开源Fortran-90软件包，应用离散偶极子近似（DDA）计算具有任意几何形状和复折射率的目标对电磁波的散射和吸收。目标可以是孤立的实体（例如，灰尘颗粒），但也可以是“目标单元”的1-D或2-D周期性阵列，其可用于研究纳米结构阵列周围的吸收、散射和电场。DDA通过可极化点的阵列来近似目标。DDA的理论及其在DDSCAT中的实现在Draine（1988）和Draine & Flatau（1994）中给出，并且在Draine & Flatau（2008）中将其扩展到周期性结构。根据Flatau & Draine（2012），可以实现高效的近场计算。DDSCAT 7.2允许精确计算尺寸参数为2*pi*aeff/lambda < 25的目标的电磁散射，前提是折射率m与1相比不太大（|m-1| < 2）。DDSCAT 7.2支持MPI、OpenMP和英特尔数学内核库（MKL）。DDSCAT 7.2支持各种目标几何形状的计算（例如，椭圆体、正四面体、长方体、有限圆柱体、六棱柱等）。目标材料可以是不均匀的和各向异性的。用户可以直接将新的目标几何图形导入代码。DDSCAT 7.2计算吸收和散射的总截面，以及针对目标相对于入射波的指定方向和指定散射方向的Mueller散射强度矩阵的选定元素。DDSCAT 7.2计算包含目标的用户指定矩形体积中的E。发行版中包含一个Fortran-90代码READNF，用于从DDSCAT 7.2创建的文件中读取E和P。
英文摘要：
DDSCAT 7.2 is a freely available open-source Fortran-90 software package applying the discrete dipole approximation (DDA) to calculate scattering and absorption of electromagnetic waves by targets with arbitrary geometries and complex refractive index. The targets may be isolated entities (e.g., dust particles), but may also be 1-d or 2-d periodic arrays of "target unit cells", which can be used to study absorption, scattering, and electric fields around arrays of nanostructures. The DDA approximates the target by an array of polarizable points. The theory of the DDA and its implementation in DDSCAT is presented in Draine (1988) and Draine & Flatau (1994), and its extension to periodic structures in Draine & Flatau (2008). Efficient near-field calculations are enabled following Flatau & Draine (2012). DDSCAT 7.2 allows accurate calculations of electromagnetic scattering from targets with size parameters 2*pi*aeff/lambda < 25 provided the refractive index m is not large compared to unity (|m-1| < 2). DDSCAT 7.2 includes support for MPI, OpenMP, and the Intel Math Kernel Library (MKL). DDSCAT 7.2 supports calculations for a variety of target geometries (e.g., ellipsoids, regular tetrahedra, rectangular solids, finite cylinders, hexagonal prisms, etc.). Target materials may be both inhomogeneous and anisotropic. It is straightforward for the user to import new target geometries into the code. DDSCAT 7.2 calculates total cross sections for absorption and scattering and selected elements of the Mueller scattering intensity matrix for specified orientation of the target relative to the incident wave, and for specified scattering directions. DDSCAT 7.2 calculates E throughout a user-specified rectangular volume containing the target. A Fortran-90 code READNF to read E and P from files created by DDSCAT 7.2 is included in the distribution.
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