Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QR, UK.
J Am Chem Soc. 2012 Mar 14;134(10):4454-6. doi: 10.1021/ja204908m. Epub 2011 Jul 27.
We show that KMnAg(CN)(2) exhibits the strongest negative linear compressibility (NLC) effect over the largest pressure range yet observed. Variable pressure neutron powder diffraction measurements reveal that its crystal lattice expands along the c axis of its trigonal cell under increasing hydrostatic pressure, while contracting along the a axis. This corresponds to a "wine-rack"-like mechanism for NLC that we find also results in anisotropic negative thermal expansion (NTE) in the same material. Inclusion of extra-framework K(+) counterions has minimal effect on framework flexibility (and hence the magnitude of NTE/NLC) but selectively frustrates the soft phonon modes responsible for destroying NLC in the related material Ag(3)[Co(CN)(6)].
我们证明 KMnAg(CN)(2) 在迄今为止观察到的最大压力范围内表现出最强的负线性压缩性（NLC）效应。变压中子粉末衍射测量表明，在静水压力下，其三方晶胞的晶格沿 c 轴膨胀，而沿 a 轴收缩。这对应于 NLC 的“酒架”样机制，我们还发现这也导致了同一种材料的各向异性负热膨胀（NTE）。额外框架的 K(+)抗衡离子的包含对框架的灵活性（因此对 NTE/NLC 的幅度）的影响最小，但选择性地阻碍了导致相关材料 Ag(3)[Co(CN)(6)]中 NLC 破坏的软声子模式。
