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Published on: July 19, 2019
Isotopic phonon effects in β-rhombohedral boron--non-statistical isotope distribution
H Werheit1, V Filipov, U Kuhlmann
1Institute of Physics, University Duisburg-Essen, Campus Duisburg, 47048 Duisburg, Germany. helmut.werheit@koeln.de
Summary
Isotopic effects in boron crystals reveal deviations from random distribution. Analysis of phonon spectra provides insights into lattice vibrations and impurity sensitivity.
Area of Science:
- Solid State Physics
- Materials Science
- Spectroscopy
Background:
- Understanding lattice dynamics is crucial for characterizing materials.
- Isotopic composition can influence material properties, including phonon behavior.
- Rhombohedral boron exhibits complex phonon spectra sensitive to its structure.
Purpose of the Study:
- To analyze isotopic phonon effects in beta-rhombohedral boron.
- To investigate the harmonic and anharmonic contributions to lattice vibrations.
- To determine the impact of isotopic disorder and impurities on phonon frequencies.
Main Methods:
- Infrared (IR) and Raman spectroscopy were used to analyze phonon spectra.
- Polycrystalline (10)B- and (11)B-enriched samples and (nat)B single crystals were studied.
- The virtual crystal approximation (VCA) was employed to model harmonic vibrations.
Main Results:
- Intra- and inter-icosahedral B-B vibrations were found to be harmonic, consistent with VCA.
- Deviations from VCA predictions were attributed to anharmonic lattice vibrations.
- Phonon shifts due to isotopic disorder in (nat)B were successfully separated and quantified.
- Some phonon frequencies showed sensitivity to impurities, indicating their influence.
- Isotopic occupation of boron sites deviated significantly from a random distribution.
Conclusions:
- Isotopic phonon effects provide specific information about phonon mode characteristics in boron.
- Anharmonicity plays a significant role in the lattice dynamics of beta-rhombohedral boron.
- The non-random distribution of isotopes suggests complex site occupancy within the boron lattice.
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