Nguyen Duong-Nguyen, Dao Duc-Anh, Miyake Takashi, Dam Hieu-Chi
Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa, 923-1292, Japan.
ESICMM, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, 305-0047, Japan.
J Chem Phys. 2020 Sep 21;153(11):114111. doi: 10.1063/5.0015977.
In this study, we investigate the structure-stability relationship of hypothetical Nd-Fe-B crystal structures using descriptor-relevance analysis and the t-SNE dimensionality reduction method. 149 hypothetical Nd-Fe-B crystal structures are generated from 5967 LA-T-X host structures in the Open Quantum Materials Database by using the elemental substitution method, with LA denoting lanthanides, T denoting transition metals, and X denoting light elements such as B, C, N, and O. By borrowing the skeletal structure of each of the host materials, a hypothetical crystal structure is created by substituting all lanthanide sites with Nd, all transition metal sites with Fe, and all light element sites with B. High-throughput first-principle calculations are applied to evaluate the phase stability of these structures. Twenty of them are found to be potentially formable. As the first investigative result, the descriptor-relevance analysis on the orbital field matrix (OFM) materials' descriptor reveals the average atomic coordination number as the essential factor in determining the structure stability of these substituted Nd-Fe-B crystal structures. 19 among 20 hypothetical structures that are found potentially formable have an average coordination number larger than 6.5. By applying the t-SNE dimensionality reduction method, all the local structures represented by the OFM descriptors are integrated into a visible space to study the detailed correlation between their characteristics and the stability of the crystal structure to which they belong. We discover that unstable substituted structures frequently carry Nd and Fe local structures with two prominent points: low average coordination numbers and fully occupied B neighboring atoms. Moreover, there are only three popular forms of B local structures appearing on all potentially formable substituted structures: cage networks, planar networks, and interstitial sites. The discovered relationships are promising to speed up the screening process for the new formable crystal structures.
在本研究中，我们使用描述符相关性分析和t-SNE降维方法研究了假设的钕铁硼晶体结构的结构-稳定性关系。通过元素替代法，从开放量子材料数据库中的5967个镧系-过渡金属-轻元素（LA-T-X）主体结构生成了149个假设的钕铁硼晶体结构，其中LA表示镧系元素，T表示过渡金属，X表示B、C、N和O等轻元素。通过借用每种主体材料的骨架结构，用Nd替代所有镧系元素位点，用Fe替代所有过渡金属位点，用B替代所有轻元素位点，创建了一个假设的晶体结构。应用高通量第一性原理计算来评估这些结构的相稳定性。发现其中20个可能可形成。作为第一个研究结果，对轨道场矩阵（OFM）材料描述符的描述符相关性分析揭示了平均原子配位数是决定这些替代钕铁硼晶体结构稳定性的关键因素。在发现可能可形成的20个假设结构中，有19个的平均配位数大于6.5。通过应用t-SNE降维方法，由OFM描述符表示的所有局部结构被整合到一个可见空间中，以研究它们的特征与所属晶体结构稳定性之间的详细相关性。我们发现不稳定的替代结构经常带有钕和铁的局部结构，有两个突出特点：平均配位数低且硼相邻原子被完全占据。此外，在所有可能可形成的替代结构上只出现了三种常见的硼局部结构形式：笼状网络、平面网络和间隙位点。所发现的关系有望加快新型可形成晶体结构的筛选过程。
