npj: 晶體的維度—如何正確計算？

近年來，二維材料的研究非常熱門。製備二維材料可以用剝離法，即從塊體的層狀材料中剝離出單層二維材料，比如從石墨中剝離出石墨烯。為了獲得更多的新型二維材料，可以利用高通量計算從材料資料庫中篩選出容易剝離的層狀材料。層狀結構篩選中的一個關鍵步驟是判斷材料中是否存在二維結構，因此需要高效準確的維度判斷算法。目前常用的維度判斷算法在處理某些複雜結構時會得到錯誤的結果。例如對於自穿插結構，已有的算法會低估它們的維度。

南京大學物理學院孫建教授團隊系統地闡述了如何利用晶體商圖這一理論工具分析晶體網絡、計算其維度。他們發現通過晶體商圖，還可以計算晶體網絡穿插多重度。作者比較了不同的晶體維度判斷算法，分析了自穿插結構對維度判斷結果的影響，解釋了穿插多重度計算方法的原理。他們用基於商圖的方法在大型材料資料庫中篩選出了數百個具有不同維度和多重度的複雜結構，發現最複雜的結構的多重度高達11。並進一步研究了篩選出來的結構的性質，發現其中一些自穿插結構具有較高氣體吸附能力和多樣的電子結構，可能在氣體存儲、選擇性催化或光催化等領域有潛在應用價值。該研究有助於更全面、準確地運用高通量方法，篩選包括低維材料在內的特定晶體結構材料。

該文近期發表於npj Computational Materials 6: 143 (2020)，英文標題與摘要如下，點擊https://www.nature.com/articles/s41524-020-00409-0可以自由獲取論文PDF。

Determining dimensionalities and multiplicities of crystal nets

Hao Gao, Junjie Wang, Zhaopeng Guo & Jian Sun

Low-dimensional materials have attracted significant attentions over the past decade. To discover new low-dimensional materials, high-throughput screening methods for structures with target dimensionality have been applied in different materials databases. For this purpose, the reliability of dimensionality identification is therefore highly important. In this work, we find that the existence of self-penetrating nets may lead to incorrect results by previous methods. In stead of this, we use the quotient graph to analyse the topologies of structures and compute their dimensionalities. Based on the quotient graph, we can calculate not only the dimensionality but also the multiplicity of self-penetrating structures. As a demonstration, we screened the Crystallography Open Database using the method and find hundreds of structures with different dimensionalities and high multiplicities up to eleven. Some of the self-penetrating materials may have application values in gas storage, selective catalysis or photocatalysis because of their high gas sorption capacities and various electronic structures.