We investigate the effect of crystal growth within a magnetic field for three polymorphic pharmaceuticals, using an experiment where the magnetic field can be varied in strength without altering other crystallization conditions. In the case of carbamazepine, fields above 0.6 T produce metastable form I, and for flufenamic acid, there is an increased propensity to crystallize metastable form I around 1 T. In contrast, the magnetic field has no effect on the crystallization of mefenamic acid, a closely related molecule. The growth of the metastable β polymorph of coronene within a magnetic field at ambient temperature is difficult to reproduce but has been seen as a minor component, consistent with this transformation to the more stable form being facile, depending on the particle size. Calculations of the diamagnetic susceptibility tensors of the polymorphs and their morphologies provide semiquantitative estimates of how the diamagnetic susceptibilities of crystallites differ between polymorphs and explain why mefenamic acid crystallization is unaffected. As the onset of crystallization of carbamazepine and coronene, as defined by changes in turbidity, occur at lower temperatures and hence greater supersaturations in certain ranges of magnetic field strength, this suggests that the field causes precipitation of the metastable form through Ostwald’s rule of stages.

中文翻译：

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强磁场在有机晶体生长过程中的应用

我们研究了在磁场中晶体生长对三种多晶型药物的影响，通过实验可以改变磁场强度而不改变其他结晶条件。在卡马西平的情况下，高于 0.6 T 的磁场会产生亚稳型 I，而对于氟芬那酸，在 1 T 左右结晶亚稳型 I 的倾向增加。 相反，磁场对甲芬那酸的结晶没有影响，密切相关的分子。在环境温度下，在磁场中晕晕亚稳态 β 多晶型物的生长难以重现，但已被视为次要成分，这与这种向更稳定形式的转变很容易（取决于粒径）一致。多晶型物的抗磁性磁化率张量及其形态的计算提供了多晶型物之间微晶的抗磁化率如何不同的半定量估计，并解释了为什么甲芬那酸结晶不受影响。由于由浊度变化定义的卡马西平和晕苯的结晶开始发生在较低温度下，因此在某些磁场强度范围内会出现更大的过饱和，这表明该场通过奥斯特瓦尔德阶段规则导致亚稳态沉淀。