反铁电PbZrO和PbHfO的再研究：80原子$Pnam$结构
A re-examination of antiferroelectric PbZrO$_3$ and PbHfO$_3$: an 80-atom $Pnam$ structure
摘要：
第一性原理密度泛函理论（DFT）对反铁电体PbZrO $_3$和PbHfO $_3$的模拟表明，它们的低温$Pbam$基态的声子谱具有动力学不稳定性.这种不稳定性使$Pbam$的$c$轴加倍，并凝聚出五种新的小振幅声子模式，从而产生80个原子的$Pnam$结构。与$Pbam$相比，该结构的稳定性略有提高，并且通过使用不同的DFT编码和不同的电子交换和相关相互作用的处理证明了其高度可重复性。这表明$Pnam$是两种材料低温基态的新候选物。有了这一发现，我们带来了平价之间的AFE原型和最近观察到的一个非常相似的AFE相掺杂或静电工程BiFeO $_3$。
英文摘要：
First principles density functional theory (DFT) simulations of antiferroelectric (AFE) PbZrO$_3$ and PbHfO$_3$ reveal a dynamical instability in the phonon spectra of their purported low temperature $Pbam$ ground states. This instability doubles the $c$-axis of $Pbam$ and condenses five new small amplitude phonon modes giving rise to an 80-atom $Pnam$ structure. Compared with $Pbam$, the stability of this structure is slightly enhanced and highly reproducible as demonstrated through using different DFT codes and different treatments of electronic exchange & correlation interactions. This suggests that $Pnam$ is a new candidate for the low temperature ground state of both materials. With this finding, we bring parity between the AFE archetypes and recent observations of a very similar AFE phase in doped or electrostatically engineered BiFeO$_3$.
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