长 τQTM 和高 Ueff 并存作为良好单分子磁体的简明标准：方形反棱镜镝单离子磁体的理论案例研究,Physical Chemistry Chemical Physics

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长 τQTM 和高 Ueff 并存作为良好单分子磁体的简明标准：方形反棱镜镝单离子磁体的理论案例研究
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2022-04-14 , DOI: 10.1039/d2cp00776b
Hong Liu ₁ , Jin-Feng Li ₂ , Bing Yin ₁

Affiliation

对一组16个方形反棱镜镝单离子磁体进行了系统的理论研究。基于从头算计算，理论上预测了磁化（QTM）时间的量子隧穿，即τ QTM_和磁反转的有效势垒U _{eff 。}理论上的τ _QTM能够识别具有最长 QTM 时间且数值偏差较小的那些。U _eff也出现类似的结果。这里拥有最佳单分子磁体 (SMM) 特性的系统正是同时具有最长τ _QTM和最高U的系统_eff，来自实验或理论。因此，我们的结果表明长τ _QTM和高U _eff的共存是高性能 SMM 的标准。尽管有其自身的局限性，但该准则很容易在大量系统中应用，因为τ _QTM和U _eff都可以通过理论预测，具有令人满意的效率和可靠性。因此，这个简洁的标准可以快速为高性能 SMM 提供筛选候选者，从而减轻进一步探索以提高精度为目标的负担。这种筛选很重要，因为进一步的探索很容易需要数十甚至数百个从头开始单个 SMM 的计算。进行半定量晶体场 (CF) 分析，并在此处显示能够以更直观的化学方式指示总体趋势。该分析有助于确定对角线和非对角线 CF 组件最重要的配位原子。因此，它可以为改善 SMM 特性提供一些直接的线索：减少轴向原子到中心离子的距离、旋转轴向原子更靠近易轴或增加其负电荷量。相应地，对赤道原子的相反操作可以得到相同的结果。

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The coexistence of long τQTM and high Ueff as a concise criterion for a good single-molecule magnet: a theoretical case study of square antiprism dysprosium single-ion magnets

A systematic theoretical study is performed on a group of 16 square antiprism dysprosium single-ion magnets. Based on ab initio calculations, the quantum tunneling of magnetization (QTM) time, i.e., τ_QTM, and effective barrier of magnetic reversal, U_eff, are theoretically predicted. The theoretical τ_QTM is able to identify the ones with the longest QTM time with small numerical deviations. Similar results occur with respect to U_eff too. The systems possessing the best single-molecule magnet (SMM) properties here are just the ones having both the longest τ_QTM and the highest U_eff, from either experiment or theory. Thus, our results suggest the coexistence of long τ_QTM and high U_eff to be a criterion for high-performance SMMs. Although having its own limits, this criterion is easy to be applied in a large number of systems since both τ_QTM and U_eff could be predicted by theory with satisfactory efficiency and reliability. Therefore, this concise criterion could provide screened candidates for high-performance SMMs quickly and, hence, ease the burden of further exploration aiming for a higher degree of precision. This screening is important since the further exploration could easily demand tens or even hundreds of ab initio calculations for a single SMM. A semi-quantitative crystal field (CF) analysis is performed and shown here to be capable of indicating the general trends in a more chemically intuitive way. This analysis could help to identify the most important coordinating atoms for both diagonal and non-diagonal CF components. Thus, it could give some direct clues for improving the SMM properties: reducing the distance of the axial atom to the central ion, rotating the axial atom closer to the easy axis or increasing the amount of its negative charge. Correspondingly, opposite operations on the equatorial atom could give the same result.

更新日期：2022-04-14

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