KNiCl3高温相中的非谐波声子。

IF 2.3 2区物理与天体物理 Q3 CHEMISTRY, PHYSICAL

Structural Dynamics-Us Pub Date : 2025-10-21 eCollection Date: 2025-09-01 DOI:10.1063/4.0000786

M J Gutmann, Kang Wang, Sun-Woo Kim, Bartomeu Monserrat, G L Pascut

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引用次数: 0

摘要

在633 K（360℃）下，利用飞行时间单晶中子衍射研究了六方卤化物钙钛矿KNiCl3的高温相。声子通过热扩散散射捕获，在能量中集成，但在动量中分解。基于密度泛函理论的谐波声子计算产生该相位的虚声子频率，表明在该理论水平上存在结构不稳定性。结果表明，包含非谐波声子-声子相互作用消除了这些不稳定性，导致与实验扩散散射良好的定性一致。这些结果表明KNiCl3的高温相是由非谐波声子-声子相互作用稳定的。

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Anharmonic phonons in the high-temperature phase of KNiCl₃.

The high-temperature phase of the hexagonal halide perovskite KNiCl₃ is investigated using time-of-flight single crystal neutron diffraction at 633 K (360 °C). Phonons are captured through thermal diffuse scattering, integrated in energy but resolved in momentum. Harmonic phonon calculations based on density functional theory yield imaginary phonon frequencies for this phase, indicating the presence of structural instabilities at this level of theory. It is shown that the inclusion of anharmonic phonon-phonon interactions removes these instabilities, leading to good qualitative agreement with the experimental diffuse scattering. These results demonstrate that the high-temperature phase of KNiCl₃ is stabilized by anharmonic phonon-phonon interactions.

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来源期刊

Structural Dynamics-Us CHEMISTRY, PHYSICALPHYSICS, ATOMIC, MOLECU-PHYSICS, ATOMIC, MOLECULAR & CHEMICAL

CiteScore

5.50

自引率

3.60%

发文量

审稿时长

16 weeks

期刊介绍： Structural Dynamics focuses on the recent developments in experimental and theoretical methods and techniques that allow a visualization of the electronic and geometric structural changes in real time of chemical, biological, and condensed-matter systems. The community of scientists and engineers working on structural dynamics in such diverse systems often use similar instrumentation and methods. The journal welcomes articles dealing with fundamental problems of electronic and structural dynamics that are tackled by new methods, such as: Time-resolved X-ray and electron diffraction and scattering, Coherent diffractive imaging, Time-resolved X-ray spectroscopies (absorption, emission, resonant inelastic scattering, etc.), Time-resolved electron energy loss spectroscopy (EELS) and electron microscopy, Time-resolved photoelectron spectroscopies (UPS, XPS, ARPES, etc.), Multidimensional spectroscopies in the infrared, the visible and the ultraviolet, Nonlinear spectroscopies in the VUV, the soft and the hard X-ray domains, Theory and computational methods and algorithms for the analysis and description of structuraldynamics and their associated experimental signals. These new methods are enabled by new instrumentation, such as: X-ray free electron lasers, which provide flux, coherence, and time resolution, New sources of ultrashort electron pulses, New sources of ultrashort vacuum ultraviolet (VUV) to hard X-ray pulses, such as high-harmonic generation (HHG) sources or plasma-based sources, New sources of ultrashort infrared and terahertz (THz) radiation, New detectors for X-rays and electrons, New sample handling and delivery schemes, New computational capabilities.