Natt Nadeem, Powell Benjamin J
School of Mathematics and Physics, The University of Queensland Brisbane Queensland 4072 Australia
Chem Sci. 2024 Oct 2;15(43):17862-72. doi: 10.1039/d4sc04225e.
A diverse range of relaxation dynamics of trapped spin-states are observed in spin crossover (SCO) materials, including exponential, sigmoidal, stretched exponential, multi-step, and mixed kinetics. We reproduce and explain this full range of relaxation behaviours using a semi-empirical, semi-classical model that combines crystal field theory with elastic inter-molecular interactions. We show that frustrated intermolecular interactions, which are responsible for multistep thermal transitions, also lead to multiple energetically competitive ordered phases, even in systems that contain only one crystallographically distinct SCO site. This rugged free energy landscape leads to dynamic disorder and thence the complex dynamics widely observed in SCO materials. Similar mechanisms are vital for understanding dynamics of more complex materials from proteins to quantum materials.
在自旋交叉（SCO）材料中观察到了捕获自旋态的多种弛豫动力学，包括指数、S形、拉伸指数、多步和混合动力学。我们使用一种半经验、半经典模型来重现和解释这一整套弛豫行为，该模型将晶体场理论与弹性分子间相互作用相结合。我们表明，导致多步热转变的受阻分子间相互作用，即使在仅包含一个晶体学上不同的SCO位点的系统中，也会导致多个能量上相互竞争的有序相。这种崎岖的自由能景观导致动态无序，从而在SCO材料中广泛观察到复杂的动力学。类似的机制对于理解从蛋白质到量子材料等更复杂材料的动力学至关重要。
