Department of Earth Sciences, University College London (UCL), Gower Street, London WC1E 6BT, UK.
Science. 2011 Feb 11;331(6018):742-6. doi: 10.1126/science.1198640.
The vast majority of materials shrink in all directions when hydrostatically compressed; exceptions include certain metallic or polymer foam structures, which may exhibit negative linear compressibility (NLC) (that is, they expand in one or more directions under hydrostatic compression). Materials that exhibit this property at the molecular level--crystalline solids with intrinsic NLC--are extremely uncommon. With the use of neutron powder diffraction, we have discovered and characterized both NLC and extremely anisotropic thermal expansion, including negative thermal expansion (NTE) along the NLC axis, in a simple molecular crystal (the deuterated 1:1 compound of methanol and water). Apically linked rhombuses, which are formed by the bridging of hydroxyl-water chains with methyl groups, extend along the axis of NLC/NTE and lead to the observed behavior.
绝大多数材料在静水压力下会向各个方向收缩；例外的包括某些金属或聚合物泡沫结构，它们可能表现出负线性压缩性（NLC）（即，它们在静水压缩下在一个或多个方向上膨胀）。在分子水平上表现出这种特性的材料——具有固有 NLC 的晶态固体——极为罕见。通过使用中子粉末衍射，我们已经在一个简单的分子晶体（甲醇和水的氘代 1:1 化合物）中发现并表征了 NLC 和极其各向异性的热膨胀，包括 NLC 轴上的负热膨胀（NTE）。由羟基-水链与甲基桥接形成的顶点连接的菱形沿 NLC/NTE 轴延伸，并导致观察到的行为。
