论文标题
纳米颗粒冻结中的均衡性多晶型物选择
Out-of-equilibrium Polymorph Selection in Nanoparticle Freezing
论文作者
论文摘要
设计不均衡的合成过程的能力开放了具有具有显着物理化学特性的纳米材料的可能性，从扩展系统中的平衡过程相比，可以从更丰富的原子体系结构调色板中进行选择。在这项工作中，我们采用原子模拟来演示如何通过纳米颗粒冻结期间的冷却速率来控制多晶型物，而Ni $ _3 $ al al，这是一种具有丰富的结构景观的材料。最新的自由能计算可以使复杂的成核过程合理化，发现两个动力学途径之间的切换，从而在室温下产生平衡结构，并在较高温度下的替代性稳态。我们的发现解决了纳米合金用于技术应用的主要挑战，即通过设计迫使该系统进入理想的亚稳态状态的治疗史，合理地利用动力学和热力学之间的竞争。
The ability to design synthesis processes that are out of equilibrium has opened the possibility of creating nanomaterials with remarkable physico-chemical properties, choosing from a much richer palette of possible atomic architectures compared to equilibrium processes in extended systems. In this work, we employ atomistic simulations to demonstrate how to control polymorph selection via cooling rate during nanoparticle freezing in the case of Ni$_3$Al, a material with a rich structural landscape. State-of-the-art free-energy calculations allow to rationalize the complex nucleation process, discovering a switch between two kinetic pathways, yielding the equilibrium structure at room temperature and an alternative metastable one at higher temperature. Our findings address the key challenge in the synthesis of nano-alloys for technological applications, i.e., rationally exploiting the competition between kinetics and thermodynamics by designing a treatment history that forces the system into desirable metastable states.
