Goodwin Andrew L, Calleja Mark, Conterio Michael J, Dove Martin T, Evans John S O, Keen David A, Peters Lars, Tucker Matthew G
Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UK.
Science. 2008 Feb 8;319(5864):794-7. doi: 10.1126/science.1151442.
We show that silver(I) hexacyanocobaltate(III), Ag3[Co(CN)6], exhibits positive and negative thermal expansion an order of magnitude greater than that seen in other crystalline materials. This framework material expands along one set of directions at a rate comparable to the most weakly bound solids known. By flexing like lattice fencing, the framework couples this to a contraction along a perpendicular direction. This gives negative thermal expansion that is 14 times larger than in ZrW2O8. Density functional theory calculations quantify both the low energy associated with this flexibility and the role of argentophilic (Ag+...Ag+) interactions. This study illustrates how the mechanical properties of a van der Waals solid might be engineered into a rigid, useable framework.
我们发现六氰合钴(III)酸银(I)，即Ag3[Co(CN)6]，呈现出正热膨胀和负热膨胀，其程度比其他晶体材料高出一个数量级。这种骨架材料沿一组方向的膨胀速率与已知最弱键合的固体相当。通过像晶格围栏一样弯曲，该骨架将这种膨胀与沿垂直方向的收缩耦合起来。这产生的负热膨胀比ZrW2O8中的负热膨胀大14倍。密度泛函理论计算量化了与这种柔韧性相关的低能量以及亲银（Ag+...Ag+）相互作用的作用。这项研究说明了如何将范德华固体的力学性能设计到一个刚性的、可用的骨架中。
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