The symmetries of a crystal are notoriously uncorrelated to those of its constituent molecules. This symmetry breaking is typically thought to occur during crystallization. Here we demonstrate that one of the two symmetry elements of olanzapine crystals, an inversion centre, emerges in solute dimers extant in solution prior to crystallization. We combine time-resolved in situ scanning probe microscopy to monitor the crystal growth processes with all-atom molecular dynamics simulations. We show that crystals grow non-classically, predominantly by incorporation of centrosymmetric dimers. The growth rate of crystal layers exhibits a quadratic dependence on the solute concentration, characteristic of the second-order kinetics of the incorporation of dimers, which exist in equilibrium with a majority of monomers. We show that growth by dimers is preferred due to overwhelming accumulation of adsorbed dimers on the crystal surface, where it is complemented by dimerization and expedites dimer incorporation into growth sites.

众所周知，晶体的对称性与其组成分子的对称性不相关。通常认为这种对称破坏发生在结晶过程中。在这里，我们证明了奥氮平晶体的两个对称元素之一，一个反转中心，在结晶之前存在于溶液中的溶质二聚体中出现。我们结合时间分辨的原位扫描探针显微镜，以全原子分子动力学模拟监测晶体生长过程。我们显示出晶体非经典地生长，主要是通过向心对称二聚体的结合。晶体层的生长速率表现出对溶质浓度的二次依赖性，溶质浓度是二聚体掺入的二级动力学特征，二聚体与大多数单体平衡存在。