RandSpg: an open-source program for generating atomistic crystal structures with specific spacegroups

A new algorithm, RandSpg, that can be used to generate trial crystal structures with specific space groups and compositions is described. The program has been designed for systems where the atoms are independent of one another, and it is therefore primarily suited towards inorganic systems. The structures that are generated adhere to user-defined constraints such as: the lattice shape and size, stoichiometry, set of space groups to be generated, and factors that influence the minimum interatomic separations. In addition, the user can optionally specify if the most general Wyckoff position is to be occupied or constrain select atoms to specific Wyckoff positions. Extensive testing indicates that the algorithm is efficient and reliable. The library is lightweight, portable, dependency-free and is published under a license recognized by the Open Source Initiative. A web interface for the algorithm is publicly accessible at http://xtalopt.openmolecules.net/randSpg/randSpg.html. RandSpg has also been interfaced with the XtalOpt evolutionary algorithm for crystal structure prediction, and it is illustrated that the use of symmetric lattices in the first generation of randomly created individuals decreases the number of structures that need to be optimized to find the global energy minimum.本文介绍了一种名为RandSpg的新型算法，可用于生成具有特定空间群（space group）与化学组成的试探晶体结构。该算法专为原子间相互独立的体系设计，因此主要适用于无机体系。所生成的晶体结构需遵循用户自定义的约束条件，包括晶格形状与尺寸、化学计量比、待生成的空间群集合，以及影响最小原子间距的相关参数。此外，用户可选择性指定是否占据最通用的威科夫位置（Wyckoff position），或将指定原子约束至特定威科夫位置。大量测试表明，该算法高效且可靠。该程序库轻量便携、无依赖，并采用获得开放源代码倡议（Open Source Initiative）认可的开源许可证发布。该算法的网页界面已公开上线，访问地址为http://xtalopt.openmolecules.net/randSpg/randSpg.html。RandSpg还已与用于晶体结构预测的XtalOpt进化算法实现对接，实验表明，在随机生成的初代种群个体中使用对称晶格，可减少寻找全局能量极小值所需优化的晶体结构数量。