Despite the general conception of brittleness, organic single crystals composed of various kinds of molecules can show ferroelasticity by mechanical twinning. This is attributed to flexibilities in molecular structures, e.g., conformation, and noncovalent bonds, e.g., length and angle. Herein, we find ferroelasticity by mechanical twinning mediated by water of crystallization in a single crystal of a zwitterion: sulfanilic acid monohydrate. Shaping of an organic single crystal is demonstrated ferroelastically from linear to bent shape and from contracted to elongated shape. Rotation of sulfonate anions along with recombination and changes in lengths and angles in flexible hydrogen bonds of small water molecules helps ferroelastic mechanical twinning. Our findings demonstrate designability of mechanically twinnable organic crystals from the viewpoints of organic chemistry and crystal engineering based on hydrogen bonds.

中文翻译：

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结晶水介导的铁弹性

尽管有脆性的一般概念，但由各种分子组成的有机单晶仍可以通过机械孪晶显示出铁弹性。这归因于分子结构的柔韧性，例如构象，以及非共价键，例如长度和角度。在本文中，我们发现两性离子：磺胺酸一水合物单晶中的结晶水介导的机械孪生引起的铁弹性。通过铁弹性从线性形状到弯曲形状以及从收缩形状到拉长形状证明了有机单晶的成形。磺酸根阴离子的旋转以及重组以及小水分子柔性氢键中长度和角度的变化有助于铁弹性机械孪生。