Related Experiment Video
Updated: Jun 1, 2026
10:40
High Resolution Phonon-assisted Quasi-resonance Fluorescence Spectroscopy
Published on: June 28, 2016
Phonons of the anomalous element cerium
Michael Krisch1, D L Farber, R Xu
1European Synchrotron Radiation Facility, B.P. 220, F-38043 Grenoble Cédex, France.
Summary
The study reveals significant changes in phonon behavior during cerium's isostructural γ-α transition, driven by altered electron-phonon interactions and contributing to the volume collapse. This research clarifies phase stability mechanisms in rare-earths.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Mechanics
Background:
- Light rare-earths and actinides properties are influenced by f electrons, but phase stability mechanisms remain unclear.
- The isostructural γ-α transition in cerium is a key area of research due to its complex behavior.
Purpose of the Study:
- To investigate the complete phonon dispersion scheme of elemental cerium during the γ-α transition.
- To compare experimental inelastic X-ray scattering data with ab initio lattice dynamics calculations.
- To elucidate the mechanism behind the isostructural volume collapse in cerium under pressure.
Main Methods:
- Inelastic X-ray scattering (IXS) to determine phonon dispersion.
- Ab initio lattice dynamics calculations for theoretical comparison.
- Analysis of lattice Grüneisen parameters and vibrational entropy change.
Main Results:
- Observed significant changes in phonon dispersion branches across the γ-α transition.
- Identified substantial modifications in electron-phonon interactions.
- Derived a vibrational entropy change of approximately (0.33+/-0.03)k(B), highlighting lattice contribution.
Conclusions:
- Lattice dynamics and electron-phonon interactions play a crucial role in cerium's isostructural γ-α transition.
- The study provides insights into the mechanism of volume collapse in cerium.
- Experimental and theoretical findings offer a comprehensive understanding of cerium phase transitions.
Related Concept Videos
03:26Electron Configuration of Multielectron Atoms
The alkali metal sodium (atomic number 11) has one more electron than the neon atom. This electron must go into the lowest-energy subshell available, the 3s orbital, giving a 1s22s22p63s1 configuration. The electrons occupying the outermost shell orbital(s) (highest value of n) are called valence electrons, and those occupying the inner shell orbitals are called core electrons. Since the core electron shells correspond to noble gas electron configurations, we can abbreviate electron...
01:27Symmetry Elements in a Crystal
Crystal symmetry operations are isometric transformations that map objects onto indistinguishable copies while preserving distances, angles, and volumes. The simplest symmetry operation is translation, which shifts the entire infinite crystal lattice parallelly by a translation vector.Crystallographic rotations involve rotations by an angle of 2π/n around an axis without changing the positions of points on the axis. It is called the rotational axis of the symmetry, denoted by n. The combination...
01:14π Electron Effects on Chemical Shift: Aromatic and Antiaromatic Compounds
In aromatic compounds, such as benzene, the circulation of (4n + 2) π-electrons sets up a diamagnetic or diatropic ring current around the perimeter of the molecule. This current induces a magnetic field that opposes the external field inside the ring and reinforces it on the outside. The protons in benzene are deshielded and exhibit high chemical shifts in the range 6.5–8.5 ppm. The shielding effect at the center of the ring is evident in complex aromatic molecules, such as annulenes. In...
01:17Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
Ideally, an unpaired electron shows a single peak in the EPR spectrum due to the transition between the two spin energy states. However, coupling interactions can occur between the spins of the unpaired electron and any neighboring spin-active nuclei. This hyperfine coupling results in hyperfine splitting, where the EPR signal is split into multiplets. The signals split into 2nI + 1 peaks, where n is the number of equivalent nuclei and I is the nuclear spin. These splitting patterns provide...
02:42Valence Bond Theory
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...
02:58Crystal Field Theory - Octahedral Complexes
Crystal Field Theory
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...
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...