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首页> 外文期刊>Acta Crystallographica, Section B. Structural Science >Predicting the Crystal Structure of Organic Molecular Materials
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Predicting the Crystal Structure of Organic Molecular Materials

机译：预测有机分子材料的晶体结构

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This paper describes a novel method for predicting the crystal structure of organic molecular materials which employs a series of successive approximations to focus on structures of high probability, without resorting to a brute force search and energy minimization of all possible structures. The problem of multiple local minima is overcome by assuming that the crystal structure is closely packed, thereby eliminating 217 of the 230 possible space groups. Configurations within the 13 remaining space groups are searched by rotating the reference molecule about Cartesian axes in rotational increments of 15°. Initial energy minimization is performed using (6-12) Lennard-Jones pair potentials to produce a set of closely packed structures. The structures are then refined with the introduction of a Coulombic potential calculated using molecular multi-pole moments. This method has successfully located local minima which correspond to the observed crystal structures of several saturated and unsaturated hydrocarbons with no a priori information provided. For large polycyclic aromatic hydrocarbons, additional refinements of the energy calculations are required to distinguish the experimental structure from a small number of closely packed structures. Our methodology for a priori crystal structure prediction represents the most efficient algorithm presented to date, in a field where the first successes have only been described within the past year and have been few and far between. Since our algorithm is capable of locating a large number of reasonable structures with similar energy in a short period of time, and is more likely to locate a minimum corresponding to the experimental structure, our program provides a superior framework to determine the level of theory required to calculate the intermolecular potential. For all but highly asymmetric hydrocarbons, however, distinguishing the observed structure from a large number of highly probable structures requires more rigorously calculated intermolecular interactions than pair potentials, plus an ad hoc electrostatic potential, and is thus beyond the scope of this paper. All calculations were performed on the Ohio Supercomputer Center's Cray Y-MP.
机译：本文介绍了一种预测有机分子材料晶体结构的新方法，该方法采用一系列连续逼近法来关注高概率结构，而无需借助蛮力搜索和所有可能结构的能量最小化。通过假设晶体结构紧密堆积，可以克服多个局部极小值的问题，从而消除了230个可能的空间群中的217个。通过使参考分子绕直角坐标轴以15°的旋转增量进行搜索，可以搜索13个剩余空间组中的构型。使用（6-12）Lennard-Jones对电位执行初始能量最小化，以产生一组紧密堆积的结构。然后通过引入使用分子多极矩计算的库仑势来精炼结构。该方法已经成功地定位了局部最小值，该局部最小值与所观察到的几种饱和和不饱和烃的晶体结构相对应，而没有提供先验信息。对于大型多环芳烃，需要对能量计算进行额外的细化，以将实验结构与少量紧密堆积的结构区分开。我们的先验晶体结构预测方法是迄今为止提出的最有效的算法，在该领域中，首次成功仅在过去一年内得到了描述，而很少成功。由于我们的算法能够在短时间内找到大量具有相似能量的合理结构，并且更有可能找到与实验结构相对应的最小值，因此我们的程序提供了一个高级框架来确定所需的理论水平计算分子间的潜力。但是，对于除高度不对称烃以外的所有烃，要从大量的高度可能的结构中区分观察到的结构，需要比对电势加上特设的静电势更严格地计算分子间相互作用，因此不在本文讨论范围之内。所有计算均在俄亥俄州超级计算机中心的Cray Y-MP上进行。

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