Coherent phonon decay and the boron isotope effect for MgB₂

Abstract

Ab initio DFT calculations for the phonon dispersion (PD) and the phonon density of states (PDOS) of the two isotopic forms ((10)B and (11)B) of MgB2 demonstrate that use of a reduced symmetry super-lattice provides an improved approximation to the dynamical, phonon-distorted P6/mmm crystal structure. Construction of phonon frequency plots using calculated values for these isotopic forms gives linear trends with integer multiples of a base frequency that change in slope in a manner consistent with the isotope effect (IE). Spectral parameters inferred from this method are similar to that determined experimentally for the pure isotopic forms of MgB2. Comparison with AlB2 demonstrates that a coherent phonon decay down to acoustic modes is not possible for this metal. Coherent acoustic phonon decay may be an important contributor to superconductivity for MgB2.

Spectroscopy of metal hexaborides: Phonon dispersion models

“…Such combinations suggest that observation of extra Raman peaks due to a constructive interference are likely. For example, we have shown for MgB 2 that the phonon mode wavenumbers can be grouped as approximate multiples of a basic harmonic frequency . Therefore, identical combination modes may be generated from multiple variants.…”

Phonon anomalies predict superconducting Tcfor AlB2-type structures

“…For endmember compositions, optimized unit cell parameters are based on literature values for MgB 2 and AlB 2 as shown in earlier work. 9,21 Schematic models of crystal structures shown in Fig. 1 are built using optimized cell parameters from CASTEP as input to the program VESTA.…”

“…We have described intrinsic sources of error for PD calculations in earlier work. 21 Estimates of error in the calculation of T d are obtained by measurement of d for both branches of the E 2g mode in the G-M and G-K reciprocal directions for each calculation (i.e. for LDA and GGA).…”

Influence of ethylene glycol on efficient photoelectrochemical activity of BiVO4 photoanode via AACVD

“…Synthesizing the films in the gas phase have advantages over liquid phase, including continuous mode of operation and high-purity products [14][15][16][17]. A method using a single-source precursor such as chemical vapor deposition (CVD) has been used to deposit highly crystalline thin films [18]. However, the high volatility of the precursor is a requirement of this method.…”