He Xing, Gupta Mayanak K, Abernathy Douglas L, Granroth Garrett E, Ye Feng, Winn Barry L, Boatner Lynn, Delaire Olivier
Department of Mechanical Engineering and Materials Science, Duke University, Durham, NC 27708.
Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
Proc Natl Acad Sci U S A. 2025 Feb 18;122(7):e2419159122. doi: 10.1073/pnas.2419159122. Epub 2025 Feb 10.
Understanding the complex temporal and spatial correlations of ions in disordered perovskite oxides is critical to rationalize their functional properties. Here, we provide insights into the longstanding controversy regarding the off-centering of transition metal (TM) ions in the archetypal ferroelectric alloy KTa[Formula: see text]Nb[Formula: see text]O[Formula: see text] (KTN). By mapping the full energy ([Formula: see text]) and wavevector ([Formula: see text]) dependence of the dynamical structure factor [Formula: see text] using neutron scattering, and rationalizing our observations with atomistic simulations leveraging machine learning, we fully resolve the static s dynamic nature of diffuse scattering sheets, as well as their composition ([Formula: see text]) and temperature dependence. Our first-principles simulations, extended with machine-learning molecular dynamics, reproduce both inelastic neutron spectra and diffuse features, and establish how dynamically correlated TM off-centerings couple to phonons, unifying local and collective viewpoints. This study sheds light into an exemplary ferroelectric system and shows the importance of mapping the full [Formula: see text] to reveal critical spatiotemporal correlations of atomic disorder from which functional properties emerge.
理解无序钙钛矿氧化物中离子复杂的时空相关性对于阐明其功能特性至关重要。在此，我们深入探讨了关于典型铁电合金KTa[化学式：见原文]Nb[化学式：见原文]O[化学式：见原文]（KTN）中过渡金属（TM）离子偏离中心的长期争议。通过利用中子散射绘制动态结构因子[公式：见原文]的全能量（[公式：见原文]）和波矢（[公式：见原文]）依赖性，并借助机器学习的原子模拟对我们的观察结果进行合理化分析，我们全面解析了漫散射片的静态和动态性质，以及它们的组成（[公式：见原文]）和温度依赖性。我们基于第一性原理的模拟通过机器学习分子动力学进行扩展，再现了非弹性中子光谱和漫射特征，并确定了动态相关的TM离子偏离中心如何与声子耦合，将局部和集体观点统一起来。这项研究为一个典型的铁电系统提供了见解，并表明绘制完整的[公式：见原文]以揭示原子无序的关键时空相关性（功能特性由此产生）的重要性。
