论文标题
在铁蛋白酶中的整个铁旋转跨界的声子分散
Phonon dispersions throughout the iron spin crossover in ferropericlase
论文作者
论文摘要
Ferropericlase（fp），（mg $ _ \ Mathrm {1-x} $ fe $ _ \ mathrm {x} $）o，是地球低地幔中第二大最丰富的阶段。在相关的压力温度条件下，FP中的铁经历高自旋（HS），s = 2，至低自旋（LS），s = 0，状态变化。现在，这种现象的性质已被充分理解，但是在这种铁状态变化过程中，仍然存在有关结构稳定性和软声子模式的基本问题。存在一般理论来解释体积减小，明显的热弹性异常以及该HS-LS跨界的广泛本质。这些理论广泛使用了准谐波近似（QHA）。因此，动态和结构稳定性对于它们的有效性至关重要。在这里，我们使用$ \ textIt {ab Initio} $ dft+USC计算研究了整个自旋交叉的FP的振动光谱。我们解决与经历了HS-LS状态变化的孤立和（第二）最近的邻居铁离子相关的振动模式。如预期的那样，这种固体解决方案的声学模式是弹性的，而光学模式受影响最大。我们表明，此HS-LS交叉上没有软声子模式，并且FP在所有相关压力下都动态稳定。
Ferropericlase (Fp), (Mg$_\mathrm{1-x}$Fe$_\mathrm{x}$)O, is the second most abundant phase in the Earths lower mantle. At relevant pressure-temperature conditions, iron in Fp undergoes a high spin (HS), S=2, to low spin (LS), S=0, state change. The nature of this phenomenon is quite well understood now, but there are still basic questions regarding the structural stability and the existence of soft phonon modes during this iron state change. General theories exist to explain the volume reduction, the significant thermo-elastic anomalies, and the broad nature of this HS-LS crossover. These theories make extensive use of the quasi-harmonic approximation (QHA). Therefore, dynamical and structural stability is essential to their validity. Here, we investigate the vibrational spectrum of Fp throughout this spin-crossover using $\textit{ab initio}$ DFT+Usc calculations. We address vibrational modes associated with isolated and (2nd) nearest neighbor iron ions undergoing the HS-LS state change. As expected, acoustic modes of this solid solution are resilient while optical modes are the most affected. We show that there are no soft phonon modes across this HS-LS crossover, and Fp is dynamically stable at all relevant pressures.
