英国曼彻斯特大学Nicholas F. Chilton团队报道了单分子磁体高温磁弛豫速率的从头算预测方法。 相关研究成果于2021年4月6日发表在国际顶尖学术期刊《美国化学会杂志》。

以[Dy（CpR）2]+阳离子（CpR是取代的环戊二烯基阴离子）为基础的有机金属分子已经成为寻找高温单分子磁体的明显领跑者。在该结构相似的分子家族中，它们的磁性发生了显著的变化，这说明了理解磁结构关系对于开发更有效的设计策略的重要性。

该文中，研究人员发展了一个从头算自旋动力学方法，并表明它能够定量预测Orbach区域的相对弛豫速率。将其应用于所有报道的[Dy（CpR）2]+阳离子，可以让研究人员了解它们弛豫动力学的差异，强调主要的判别标准是晶体场分裂的大小，而不是自旋-振动耦合的差异。

随后，研究人员利用该方法预测了一系列假设的有机金属三明治化合物的弛豫速率，揭示了现有化合物已达到的2100–2200 K左右的有效磁弛豫势垒上限。结果表明，单金属单分子磁体的进一步改进需要利用电子激发将振动模式脱离共振。

附：英文原文

Title: Ab Initio Prediction of High-Temperature Magnetic Relaxation Rates in Single-Molecule Magnets

Author: Daniel Reta, Jon G. C. Kragskow, Nicholas F. Chilton

Issue&Volume: April 6, 2021

Abstract: Organometallic molecules based on [Dy(CpR)2]+ cations (where CpR is a substituted cyclopentadienyl anion) have emerged as clear front-runners in the search for high-temperature single-molecule magnets. Within this family of structurally similar molecules, significant variations in their magnetic properties are seen, demonstrating the importance of understanding magneto-structural relationships to develop more efficient design strategies. Here we develop an ab initio spin dynamics methodology and show that it is capable of quantitative prediction of relative relaxation rates in the Orbach region. Applying it to all reported [Dy(CpR)2]+ cations allows us understand differences in their relaxation dynamics, highlighting that the main discriminant is the magnitude of the crystal field splitting, rather than differences in spin-vibrational coupling. We subsequently employ the method to predict relaxation rates for a series of hypothetical organometallic sandwich compounds, revealing an upper limit to the effective barrier to magnetic relaxation of around 2100–2200 K, which has been reached by existing compounds. Our conclusion is that further improvements to monometallic single-molecule magnets require moving vibrational modes off-resonance with electronic excitations.

DOI: 10.1021/jacs.1c01410

Source: https://pubs.acs.org/doi/10.1021/jacs.1c01410