Bi Tiange, Eggers Bryce T, Cohen R E, Campbell Branton J, Strobel Timothy
Earth and Planets Laboratory, Carnegie Institution for Science, 5241 Broad Branch Road, Northwest, Washington, D.C., Washington 20015, United States.
Department of Physics and Astronomy, Brigham Young University, Provo, Utah 84602, United States.
J Am Chem Soc. 2024 Mar 27;146(12):7985-7997. doi: 10.1021/jacs.3c08362. Epub 2023 Dec 5.
Boron substitution represents a promising approach to stabilize carbon clathrate structures, but no thermodynamically stable substitution schemes have been identified for frameworks other than the type-VII (sodalite) structure type. To investigate the possibility for additional tetrahedral carbon-based clathrate networks, more than 5000 unique boron decoration schemes were investigated computationally for type-I and type-II carbon clathrates with a range of guest elements including Li, Na, K, Rb, Cs, Mg, Ca, Sr, and Ba. Density functional theory calculations were performed at 10 and 50 GPa, and the stability and impact of boron substitution were evaluated. The results indicate that the boron-substituted carbon clathrates are stabilized under high-pressure conditions. Full cage occupancies of intermediate-sized guest atoms (e.g., Na, Ca, and Sr) are the most favorable energetically. Clathrate stability is maximized when the boron atoms are substituted within the hexagonal rings of the large [56]/[56] cages. Several structures with favorable formation enthalpies <-200 meV/atom were predicted, and type-I CaBC is on the convex hull at 50 GPa. This structure represents the first thermodynamically stable type-I clathrate identified and suggests that boron-substituted carbon clathrates may represent a large family of diamond-like framework materials with a range of structure types and guest/framework substitutions.
硼取代是稳定碳笼状结构的一种有前景的方法，但除了VII型（方钠石）结构类型外，尚未确定其他框架的热力学稳定取代方案。为了研究额外的四面体碳基笼状网络的可能性，通过计算研究了5000多种独特的硼修饰方案，用于I型和II型碳笼合物，其中包含一系列客体元素，如Li、Na、K、Rb、Cs、Mg、Ca、Sr和Ba。在10 GPa和50 GPa下进行了密度泛函理论计算，并评估了硼取代的稳定性和影响。结果表明，硼取代的碳笼合物在高压条件下得以稳定。中等尺寸客体原子（如Na、Ca和Sr）的完全笼占据在能量上是最有利的。当硼原子取代大[56]/[56]笼的六元环内的原子时，笼合物的稳定性最大化。预测了几种形成焓<-200 meV/原子的有利结构，并且I型CaBC在50 GPa下处于凸包上。这种结构代表了首次确定的热力学稳定的I型笼合物，并表明硼取代的碳笼合物可能代表一大类具有一系列结构类型和客体/框架取代的类金刚石骨架材料。
