Related Experiment Video
Updated: Jun 13, 2025
High Pressure Single Crystal Diffraction at PX^2
Published on: January 16, 2017
Columbite Single-Crystal CoV2O6 under High Pressure: An XRD and Raman Spectroscopy Study
Josu Sánchez-Martín1, Pierre Bouvier2, Gaston Garbarino3
1Departamento de Física Aplicada-ICMUV, Universidad de Valencia, Dr. Moliner 50, Burjassot, Valencia 46100, Spain.
None:
The application of high pressure to orthorhombic columbite CoV2O6 resulted in two phase transitions, characterized by single-crystal X-ray diffraction (XRD) and Raman spectroscopy up to 54.9(1) GPa. The first phase transition, at 20.0(1) GPa, is isostructural, preserving the space group (Pbcn) but implies a sudden volume reduction (4.7%) and a symmetrization of VO6 octahedra, as well as a group shift of the vibrational modes toward higher wavenumbers. The named columbite-II structure remains stable up to 45.6(1) GPa. Beyond this pressure, a different monoclinic polymorph (space group P21/c) was deduced from the high-quality diffraction data. The two observed phase transitions are reversible, but below 4.9(3) GPa, the sample mainly transforms into the previously known brannerite polymorph. The anisotropic compressibility of the lattice axis and the Birch-Murnaghan equation of state were obtained from the XRD analysis. Our experimental results are supported by density functional theory calculations.
Related Concept Videos
01:10X-ray Diffraction of Biological Samples
According to Bragg's law, when X-rays strike the sample positioned on a stage, the rays are scattered by the electron clouds around the sample atoms. The X-ray diffraction or scattering is caused by constructive interference of the X-ray waves that reflect off the internal...
01:20Raman Spectroscopy: Overview
However, a small fraction of the scattered light exhibits a frequency shift due to the exchange of energy between the incident photons and...
01:26Raman Spectroscopy Instrumentation: Overview
The monochromatic laser source, typically using visible or near-infrared radiation, generates a highly focused beam of light. This light interacts with the molecules of the sample, scattering some of the light. Liquid and gaseous samples are usually tested in ordinary glass capillaries, while solids can be analyzed as powders packed in capillaries or as potassium...
02:46Crystal Field Theory - Tetrahedral and Square Planar 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,...
02:58Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
02:18X-ray Crystallography
Diffraction
Diffraction is the change in the direction of travel experienced by an electromagnetic wave when it encounters a physical barrier whose dimensions are comparable to those of the wavelength of the light. X-rays are electromagnetic radiation with wavelengths about as long as the distance between neighboring...