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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >The lines-of-force landscape of interactions between molecules in crystals; Cohesive versus tolerant and collateral damage contact
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The lines-of-force landscape of interactions between molecules in crystals; Cohesive versus tolerant and collateral damage contact

机译：晶体中分子之间相互作用的力线图;内聚性，耐受性和附带损害接触

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摘要

A quantitative analysis of relative stabilities in organic crystal structures is possible by means of reliable calculations of interaction energies between pairs of molecules. Such calculations have been performed by the PIXEL method for 1108 non-ionic and 98 ionic organic crystals, yielding total energies and separate Coulombic polarization and dispersive contributions. A classification of molecule-molecule interactions emerges based on pair energy and its first derivative, the interaction force, which is estimated here explicitly along an approximate stretching path. When molecular separation is not at the minimum-energy value, as frequently happens, forces may be attractive or repulsive. This information provides a fine structural fingerprint and may be relevant to the mechanical properties of materials. The calculations show that the first coordination shell includes destabilizing contacts in 9% of crystal structures for compounds with highly polar chemical groups (e.g. CN, NO_2, SO_2). Calculations also show many pair contacts with weakly stabilizing (neutral) energies; such fine modulation is presumably what makes crystal structure prediction so difficult. Ionic organic salts or zwitterions, including small peptides, show a Madelung-mode pairing of opposite ions where the total lattice energy is stabilized from sums of strongly repulsive and strongly attractive interactions. No obvious relationships between atom-atom distances and interaction energies emerge, so analyses of crystal packing in terms of geometrical parameters alone should be conducted with due care.
机译：借助可靠的分子对之间相互作用能的可靠计算，可以对有机晶体结构中的相对稳定性进行定量分析。已经通过PIXEL方法对1108个非离子和98个离子有机晶体进行了此类计算，从而产生了总能量以及库仑极化和色散贡献。基于对能量及其一阶导数，即相互作用力，出现了分子-分子相互作用的分类，此处明确地沿近似拉伸路径对其进行了估算。当分子分离未达到最小能量值时（如经常发生的那样），力可能具有吸引力或排斥力。该信息提供了良好的结构指纹，并且可能与材料的机械性能有关。计算表明，对于具有高极性化学基团（例如CN，NO_2，SO_2）的化合物，第一配位壳包含9％的晶体结构中的不稳定接触。计算还表明，许多对触点具有弱稳定的（中性）能量。这种精细的调制可能使晶体结构的预测变得如此困难。离子有机盐或两性离子，包括小肽，表现出相反离子的马德隆模式配对，其中总的晶格能量由强烈排斥和强烈吸引的相互作用的总和稳定。原子与原子之间的距离与相互作用能之间没有明显的联系，因此仅在进行几何参数分析时应格外小心。

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