具有岩盐结构的BaS-PbS体系中的铁电性和反铁电性
Ferroelectricity and antiferroelectricity in the BaS-PbS system with the rocksalt structure
AI总结：
研究了BaS-PbS体系中多种结构的铁电不稳定性，用第一性原理计算发现其与TO声子不稳定性有关，除铁电相外还有反铁电相及混合相，能量接近暗示低温可能出现非遍历性。
AI中文摘要：
利用密度泛函理论中的第一性原理计算，发现并研究了具有NaCl结构的BaS - PbS体系中，超结构、超晶格、量子线和无序固溶体中的铁电不稳定性。这些结构中铁电性的出现与线性 -Pb - S - Pb - S - 链中TO声子的不稳定性有关，这是由于引入大的钡原子后结构拉伸所致。此外，还发现除了铁电相，这些结构还呈现稳定的、与之竞争的反铁电相以及具有混合铁电 - 反铁电有序的相（铁电极化的一维Pb - S链在垂直方向上有序或无序排列）。这些相常成为研究体系的基态。铁电、反铁电和混合态能量接近，表明在构型空间中出现了具有无限多个阱且被势垒隔开的多极小势，这暗示了结构在低温下可能出现非遍历性。
英文摘要：
The ferroelectric instability in superstructures, superlattices, quantum wires, and disordered solid solutions in the BaS--PbS system with the NaCl structure has been discovered and investigated using first-principles calculations within the density functional theory. The emergence of ferroelectricity in these structures is associated with the instability of TO phonons in linear --Pb--S--Pb--S-- chains, which arises as a result of stretching of the structures upon the introduction of large barium atoms. Additionally, it has been discovered that, alongside ferroelectric phases, the structures also exhibit stable, competing antiferroelectric phases and those with a mixed ferroelectric--antiferroelectric ordering (ferroelectrically polarized one-dimensional Pb--S chains arranged in an ordered or disordered manner in the perpendicular direction). These phases often become the ground state of the studied systems. The closeness of the energies of the ferroelectric, antiferroelectric, and mixed states indicates the emergence of a multi-minimum potential with an infinite number of wells separated by potential barriers in the configuration space. This suggests a possible emergence of nonergodicity in the structures at low temperatures.
