Related papers: Superstructure reflexions in tilted perovskites Pa…
In a previous article (Beanland & Sjokvist, 2024), we derived Boolean conditions for the appearance of superstructure reflexions in diffraction patterns from perovskites with tilted oxygen octahedra, using the structure factor equation.…
Ion displacements are the cause of the ferroelectricity in perovskites. By properly shifting ions, ab initio computations have been extensively used to investigate properties of perovsites in various structural phases. In addition to the…
Halide perovskites have been extensively studied as materials of interest for optoelectronic applications. There is a major emphasis on ways to tailor the stability, defect behavior, electronic band structure, and optical absorption in…
Antiperovskites share the same structure as perovskites, but allow completely different chemistries and nominal charge states of anions to be stabilized. This gives rise to many interesting phenomena, including septet superconductivity and…
Pinwheel patterns and their higher dimensional generalisations display continuous circular or spherical symmetries in spite of being perfectly ordered. The same symmetries show up in the corresponding diffraction images. Interestingly, they…
A mathematical framework is developed to describe tilted perovskites using a tensor description of octahedral deformations. The continuity of octahedral tilts through the crystal is described using an operator which relates the deformations…
A single crystal of GdBaCo2O5.47(2) has been studied by means of X-ray diffraction. Appearance of superstructure reflections at T = 341.5(7) K gives an evidence of continuous transition to the phase with unit cell doubled along the shortest…
Perovskites have been applied in a wide range of fields such as solar cells and non-volatile memories due to their multiferroic nature and excellent photo-electric conversion capabilities. Recently, two-dimensional (2D) perovskites with a…
Oxygen octahedral distortions including tilts/rotations, deformations and off-centering in (layered) perovskites play the key role in their numerous functional properties. At the polar-centrosymmetric phase boundary in bi-layered perovskite…
The list of possible commensurate phases obtained from the parent tetragonal phase of perovskites by allowing the tilting of octahedra of oxygen ions is reexamined. It is found that many structures allowed by symmetry are not consistent…
Local and fast structural probes using synchrotron radiation have shown nanoscale striped puddles and nanoscale phase separation in doped perovskites.It is known that the striped phases in doped perovskites are due to competing interactions…
Diffraction images with continuous rotation symmetry arise from amorphous systems, but also from regular crystals when investigated by powder diffraction. On the theoretical side, pinwheel patterns and their higher dimensional…
We study the antiferrodistortive instability and its interaction with ferroelectricity in cubic perovskite compounds. Our first-principles calculations show that coexistence of both instabilities is very common. We develop a…
Two-dimensional (2D) ferroelectricity has attracted extensive attention since its discovery in the monolayers of van der Waals materials. Here we show that 2D ferroelectricity induced by octahedral rotation distortion is widely present in…
Halide perovskites have emerged as one of the most interesting materials for optoelectronic applications due to their favorable properties, such as defect-tolerance and long charge carrier lifetimes, which are attributed to their dynamic…
Despite the simplicity of the original perovskite crystal structure, this family of compounds shows an enormous variety of structural modifications and variants. In the following, we will describe several examples of perovskites, their…
Halide perovskites, with prototype cubic phase ABX3, undergo various phase transitions accompanied by rigid rotations of corner-sharing BX6 octahedra. Using first-principles density functional theory calculations, we have performed a…
The ability to control the structure of a crystalline solid on ultrafast timescales bears enormous potential for information storage and manipulation or generating new functional states of matter [1]. In many materials where the ultrafast…
The oxide heterostructure [(YFeO$_3$)$_5$(LaFeO$_3$)$_5$]$_{40}$, which is magnetically ordered and piezoelectric at room temperature, has been constructed from two weak ferromagnetic AFeO$_3$ perovskites with different A cations using…
High-temperature phase behavior in the system LixNa1-xNbO3 has been studied by using high-resolution powder neutron diffraction. Each of the three compositions studied in the Na-rich part of the phase diagram (x = 0.03, 0.08 and 0.12) shows…