Multi-phase ELAStic Aggregates (MELASA) software tool for modeling anisotropic elastic properties of lamellar composites

We introduce a new web-based tool called MELASA (Multi-phase ELAStic Aggregates), open-access available at https://melasa.cerit-sc.cz, for computations and visualizations of anisotropic elastic properties of lamellar (nano-)composites. MELASA implements a linear-elasticity method by Grimsditch and Nizzoli (1986), originally developed for superlattices of any symmetry. Our tool may be used for computation of anisotropic elastic properties of a specific type of periodically separated lamellar (nano-)composites using matrices of elastic stiffnesses of co-existing phases as an input. Elastic properties are visualized in the form of directional dependencies of selected elastic characteristics (Young’s modulus and linear compressibility). MELASA further generalizes the Grimsditch–Nizzoli approach, which was originally formulated for only two phases, to multiple-phase composites. Additionally, our implementation allows for treating internal rotations of local coordination systems corresponding to the natural set of coordinates that match directional vectors of unit cell defining crystal lattice within the co-existing phases. Fe–Al-based superalloy nanocomposites are employed as a numerical example of superlattices with the input and output elastic stiffnesses determined by quantum-mechanical calculations. In particular, three different atomic configurations of interfaces in superlattices containing the ordered Fe_3 Al phase and a disordered Fe–Al phase with 18.75at.%Al (modeled by a special quasi-random structure, SQS) are considered. They differ by relative positions of sublattices in Fe_3 Al (an antiphase-like shift) and/or atomic planes in Fe-18.75at.%Al with respect to the interface (a circular/cyclic shift).本研究介绍一款全新的网页端工具MELASA（多相弹性聚集体，Multi-phase ELAStic Aggregates），其开放获取地址为https://melasa.cerit-sc.cz，可用于层状（纳米）复合材料各向异性弹性性质的计算与可视化。该工具实现了Grimsditch与Nizzoli于1986年提出的线弹性方法，该方法最初是为任意对称性超晶格开发的。本工具可通过输入共存相的弹性刚度矩阵，计算一类特定的周期性层状（纳米）复合材料的各向异性弹性性质。弹性性质将以选定弹性特征（杨氏模量与线性压缩率）的方向依赖性形式进行可视化展示。此外，MELASA将原本仅针对两相复合材料提出的Grimsditch-Nizzoli方法推广至多相复合材料场景。同时，本工具支持对共存相内与定义晶格的晶胞方向矢量匹配的自然坐标系所对应的局部配位系统进行内部旋转变换处理。本研究以铁铝基高温合金纳米复合材料作为超晶格的数值算例，其输入与输出弹性刚度均通过量子力学计算得到。具体而言，本研究针对包含有序Fe₃Al相与18.75at.%Al无序Fe-Al相（通过特殊准随机结构（SQS，special quasi-random structure）建模）的超晶格，分析了三种不同的界面原子构型。这三种构型的差异体现在Fe₃Al中亚晶格的相对位置（类反相位移）和/或Fe-18.75at.%Al中的原子平面相对于界面的位置（环形/循环位移）。