Faculty of Chemistry, Adam Mickiewicz University, Umultowska 89b, Poznań 61-614, Poland.
Nat Commun. 2014 Jul 4;5:4337. doi: 10.1038/ncomms5337.
Materials with negative linear compressibility are sought for various technological applications. Such effects were reported mainly in framework materials. When heated, they typically contract in the same direction of negative linear compression. Here we show that this common inverse relationship rule does not apply to a three-dimensional metal-organic framework crystal, [Ag(ethylenediamine)]NO3. In this material, the direction of the largest intrinsic negative linear compression yet observed in metal-organic frameworks coincides with the strongest positive thermal expansion. In the perpendicular direction, the large linear negative thermal expansion and the strongest crystal compressibility are collinear. This seemingly irrational positive relationship of temperature and pressure effects is explained and the mechanism of coupling of compressibility with expansivity is presented. The positive coupling between compression and thermal expansion in this material enhances its piezo-mechanical response in adiabatic process, which may be used for designing new artificial composites and ultrasensitive measuring devices.
人们一直在寻找具有负线性压缩率的材料，以应用于各种技术领域。此类效应主要在骨架材料中被报道。当它们被加热时，通常会沿着负线性压缩的同一方向收缩。在这里，我们展示了这一常见的反相关规律并不适用于一种三维金属有机骨架晶体[Ag(乙二胺)]NO3。在该材料中，人们观察到金属有机骨架中迄今为止最大的固有负线性压缩方向与最强的正热膨胀方向一致。在垂直方向上，大的线性负热膨胀和最强的晶体压缩率是共线的。这种温度和压力效应之间看似不合理的正相关关系得到了解释，并提出了压缩率与膨胀率耦合的机制。在这种材料中，压缩和热膨胀之间的正耦合增强了其在绝热过程中的压电力响应，这可能用于设计新型人工复合材料和超灵敏测量设备。
