Mechanical Anisotropy in Crystalline Saccharin: Nanoindentation Studies
Mechanical Anisotropy in Crystalline Saccharin: Nanoindentation Studies
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DOI：
10.1021/cg1009362
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发表时间：
2010-10-01
影响因子：
3.8
通讯作者：
Desiraju, Gautam R.
中科院分区：
文献类型：
--
作者：
Kiran, M. S. R. N.;Varughese, Sunil;Desiraju, Gautam R.
利用纳米压痕技术研究了糖精单晶的力学性能与其内部结构的关系。在（100）和（011）面上进行压痕以评估机械各向异性。载荷-位移（P-h）曲线表明两个面上塑性变形的性质存在显著差异。在（011）平面上得到的P-h曲线比较光滑，反映了均匀塑性。然而，在（100）平面上获得的P-h曲线中观察到位移爆发（pop-ins），表明离散变形机制。虽然糖精在很大程度上具有三维紧密堆积结构，但在两个面上的硬度和模量存在微小差异，这在一定程度上是合理的。从氢键网络的维数角度讨论了（100）和（011）两种不同形变机制的结构根源。在（100）平面下，糖精二聚体堆叠并通过主要在芳环之间的非特异性货车德旺相互作用而稳定。然而，在（011）平面下，分子被更定向和交联的C-H稳定。O氢键。晶体堆积和相互作用的这种各向异性反映在这些面上的机械行为中。与弹出相关的位移被发现是旧分子分离距离的整数倍。纳米压痕提供了一个机会，比较实验，并以定量的方式，各种分子间的相互作用，火灾目前在分子晶体。
The nanoindentation technique has been employed to relate the mechanical properties of saccharin single crystals with their internal structure. Indentations were performed on (100) and (011) faces to assess the mechanical anisotropy. The load-displacement (P-h) curves indicate significant differences in the nature of the plastic deformation on the two faces. The P-h curves obtained on the (011) plane are smooth, reflecting homogeneous plasticity. However, displacement bursts (pop-ins) are observed in the P-h curves obtained on the (100) plane suggesting a discrete deformation mechanism. Marginal differences exist in the hardness and modulus on the two faces that may, in part, be rationalized, although one notes that saccharin has a largely three-dimensional close-packed structure. The structural origins of the fundamentally different deformation mechanisms on (100) and (011) are discussed in terms of the dimensionality of the hydrogen bonding networks. Down the (100) planes, the saccharin dimers are stacked and are stabilized by nonspecific van der Wants interactions mostly between aromatic rings. However, down the (011) planes, the molecules are stabilized by more directional and cross-linked C-H ... O hydrogen bonds. This anisotropy in crystal packing and interactions is reflected in the mechanical behavior on these faces. The displacements associated with the pop-ins were found to he integral multiples oldie molecule separation distances. Nanoindentation offers an opportunity to compare experimentally, and in a quantitative way, the various intermolecular interactions that fire present in a molecular crystal.