AI 中文总结
该研究提出 QENS-IFWS 全局拟合方法，结合新戊二醇及其衍生物，揭示羟甲基旋转活化能与氢键网络稳定性的关联，为 barocaloric 分子晶体设计提供通用工具。
AI 中文摘要
barocaloric（BC）分子晶体具有有序-无序相变，为固态加热和冷却提供了有前景的基础。然而，合理设计这些下一代材料需要对驱动转变熵变的分子动力学有微观层面的理解。准弹性中子散射（QENS）技术，包括非弹性固定窗口扫描（IFWSs），能够直接探测热力学相变过程中的这类分子运动。本文提出一种 QENS-IFWS 全局拟合方法，用于系统研究支撑分子晶体 BC 性能的分子动力学。我们在新戊二醇（NPG）及三种衍生物上验证了该方法，这些衍生物通过不同化学途径实现了动力学扰动。通过固定所有样品的尝试频率，我们观察到羟甲基旋转和全分子旋转的相对活化能与可动分数存在可测量差异，其中羟甲基旋转活化能的变化最为显著，与氢键网络稳定性密切相关，衍生物相较于纯 NPG 的变化范围为 -3.6% 至 +11.1%。这种全局拟合策略提取分子旋转细微变化的能力，凸显了 QENS 作为指导 BC 分子晶体设计的通用工具的价值。
英文摘要
Barocaloric (BC) molecular crystals exhibit order-disorder phase transitions that o9er a promising basis for solid-state heating and cooling. However, rational design of these next-generation materials requires microscopic understanding of the molecular dynamics that drive the transitional entropy change. Quasi-elastic neutron scattering (QENS) techniques including inelastic fixed-window scans (IFWSs) enable the direct probing of such molecular motions throughout thermodynamic phase transitions. Here we present a QENS-IFWS global fitting methodology for systematically investigating the molecular dynamics underpinning BC performance in molecular crystals. We demonstrate this methodology on neopentyl glycol (NPG) and three derivatives spanning chemically distinct routes to dynamical perturbation. By fixing attempt frequencies across samples, we observe measurable differences in the relative activation energies and mobile fractions of hydroxymethyl and full-molecular rotations. The largest observed e9ect is on the hydroxymethyl rotation activation energies, which is closely related to hydrogen bond network stability, ranging from -3.6% to +11.1% in the derivatives compared to pure NPG. The capability of this global fitting strategy to extract subtle variations in molecular rotations highlights QENS as a versatile design tool for guiding BC molecular crystal design.
CommentsMain manuscript (19 pages 5 figures) followed by supplementary information (15 pages 19 figures)
