Related Experiment Video
Updated: Jul 2, 2025
08:12
Low Pressure Vapor-assisted Solution Process for Tunable Band Gap Pinhole-free Methylammonium Lead Halide Perovskite Films
Published on: September 8, 2017
9.6K
Structural Properties of Some Vacancy-Ordered Platinum Halide Perovskites
Caleb J Bennett1, Helen E A Brand2, Alexander K L Yuen1
1School of Chemistry, University of Sydney, F11, Sydney, NSW 2006, Australia.
Inorganic Chemistry
|February 27, 2024
Summary
Dehydration of sodium hexahaloplatinates (Na2PtX6·6H2O) forms vacancy-ordered perovskites due to small Na cations. Larger alkali metals yield stable anhydrous hexahalides, with potassium salts exhibiting temperature-dependent structural phase transitions and octahedral tilting.
Area of Science:
- Solid-state chemistry
- Crystallography
- Materials science
Background:
- The dehydration of hexahydrated alkali metal hexahaloplatinates (A2PtX6·6H2O) is crucial for understanding their structural transformations.
- The role of cation size in stabilizing anhydrous phases and influencing crystal symmetry is a key area of investigation.
Purpose of the Study:
- To investigate the structural changes during the dehydration of Na2PtX6·6H2O (X = Cl, Br) using in situ synchrotron X-ray diffraction.
- To explore the impact of different alkali metal cations (Na, K, Rb, Cs) on the formation and stability of anhydrous hexahaloplatinate structures.
- To characterize the phase transitions and cooperative tilting of PtX6 octahedra in relation to temperature and cation size.
Main Methods:
- In situ variable temperature synchrotron X-ray diffraction was employed to study the dehydration process.
- Crystal structures were analyzed to identify phase transitions and symmetry changes.
- Glazer tilt notation was used to describe the cooperative tilting of PtX6 octahedra.
Main Results:
- Dehydration of Na2PtX6·6H2O yields vacancy-ordered double perovskites (Na2PtX6) due to the small Na cation, causing PtX6 octahedra tilting and symmetry reduction.
- Larger alkali metals (K, Rb, Cs) facilitate the formation of stable anhydrous hexahalides, which showed no tendency to hydrate.
- Potassium hexahaloplatinates (K2PtBr6, K2PtI6) exhibited temperature-dependent phase transitions from cubic (Fm3̅m) to tetragonal (P4/mnc) and finally to monoclinic (P21/n) structures, associated with increasing PtX6 octahedra tilting.
Conclusions:
- The size of the alkali metal cation significantly influences the structural outcome of hexahaloplatinate dehydration.
- Cooperative tilting of PtX6 octahedra is a key mechanism driving symmetry lowering in these compounds.
- Understanding these phase transitions is vital for designing and utilizing novel inorganic materials.
Related Concept Videos
02:42Valence Bond Theory
8.6K
Coordination compounds and complexes exhibit different colors, geometries, and magnetic behavior, depending on the metal atom/ion and ligands from which they are composed. In an attempt to explain the bonding and structure of coordination complexes, Linus Pauling proposed the valence bond theory, or VBT, using the concepts of hybridization and the overlapping of the atomic orbitals. According to VBT, the central metal atom or ion (Lewis acid) hybridizes to provide empty orbitals of suitable...
8.6K
02:37Metallic Solids
18.4K
Metallic solids such as crystals of copper, aluminum, and iron are formed by metal atoms. The structure of metallic crystals is often described as a uniform distribution of atomic nuclei within a “sea” of delocalized electrons. The atoms within such a metallic solid are held together by a unique force known as metallic bonding that gives rise to many useful and varied bulk properties.
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability....
All metallic solids exhibit high thermal and electrical conductivity, metallic luster, and malleability....
18.4K
02:42Ionic Crystal Structures
14.3K
Ionic crystals consist of two or more different kinds of ions that usually have different sizes. The packing of these ions into a crystal structure is more complex than the packing of metal atoms that are the same size.
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
Most monatomic ions behave as charged spheres, and their attraction for ions of opposite charge is the same in every direction. Consequently, stable structures for ionic compounds result (1) when ions of one charge are surrounded by as many ions as possible of the opposite...
14.3K
04:01VSEPR Theory and the Effect of Lone Pairs
42.3K
Effect of Lone Pairs of Electrons on Molecule Geometry
42.3K
02:33Lattice Centering and Coordination Number
9.6K
The structure of a crystalline solid, whether a metal or not, is best described by considering its simplest repeating unit, which is referred to as its unit cell. The unit cell consists of lattice points that represent the locations of atoms or ions. The entire structure then consists of this unit cell repeating in three dimensions. The three different types of unit cells present in the cubic lattice are illustrated in Figure 1.
Types of Unit Cells
Imagine taking a large number of identical...
Types of Unit Cells
Imagine taking a large number of identical...
9.6K
02:46Crystal Field Theory - Tetrahedral and Square Planar Complexes
42.5K
Tetrahedral Complexes
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
Crystal field theory (CFT) is applicable to molecules in geometries other than octahedral. In octahedral complexes, the lobes of the dx2−y2 and dz2 orbitals point directly at the ligands. For tetrahedral complexes, the d orbitals remain in place, but with only four ligands located between the axes. None of the orbitals points directly at the tetrahedral ligands. However, the dx2−y2 and dz2 orbitals (along the Cartesian axes) overlap with the ligands less than the dxy,...
42.5K