Phonon Unfolding : A program for unfolding phonon dispersions of materials

Zheng, Fawei; Zhang, Ping

doi:10.1016/j.cpc.2016.09.005

Cited by 16 publications

(16 citation statements)

References 49 publications

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“…The calculated supercell phonon dispersions were subsequently unfolded into the first BZ of the primitive B1 structure using the phonon unfolding method [33][34][35] . We adopted a plane-wave based unfolding procedure 36 , which projects the supercell modes into plane-wave-like modes with wave-numbers q in the first BZ of the B1 structure. This procedure is useful to identify changes in phonon dispersions caused by heavy translational symmetry breaking, as is the case here.…”

Section: Methodsmentioning

confidence: 99%

Phonon dispersion throughout the iron spin crossover in ferropericlase

2020

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Ferropericlase (Fp), (Mg1-xFex)O, is the second most abundant phase in the Earth's lower mantle.At relevant pressure-temperature conditions, iron in Fp undergoes a high spin (HS), S=2, to low spin (LS), S=0, state change. The nature of this phenomenon is quite well understood now, but there are still basic questions regarding the structural stability and the existence of soft phonon modes during this iron state change. General theories exist to explain the volume reduction, the significant thermo-elastic anomalies, and the broad nature of this HS-LS crossover. These theories make extensive use of the quasi-harmonic approximation (QHA). Therefore, dynamical and structural stability is essential to their validity. Here, we investigate the vibrational spectrum of Fp throughout this spin-crossover using ab initio DFT+Usc calculations. We address vibrational modes associated with isolated and (2 nd ) nearest neighbor iron ions undergoing the HS-LS state change. As expected, acoustic modes of this solid solution are resilient while optical modes are the most affected. We show that there are no soft phonon modes across this HS-LS crossover, and Fp is dynamically stable at all relevant pressures.

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Section: Methodsmentioning

confidence: 99%

Phonon dispersion throughout the iron spin crossover in ferropericlase

2020

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“…To allow for a comparable representation, the phonon dispersion curves were back-folded on the high-symmetry directions (Γ--K-M-Γ) of reciprocal lattice of graphite. This was achieved by applying Phonon Unfolding code 25 . The electronic band structure was treated in a similar way, also applying a back-folding scheme with respect to highsymmetry directions in the reciprocal lattice of graphite, as provided within the BandUp code 26,27 .…”

Section: Computationalmentioning

confidence: 99%

Alkali metal insertion into hard carbon – the full picture

et al. 2020

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“…Note that if the phonon-associated property is zero, such as the electron-phonon coupling strength in zigzag graphene nanoribbons with even dimers (due to the selection rule of the parity conservation) [31], then the contribution of each BM is also zero. Similar projection procedures have been applied for other purposes, such as unfolding the phonon dispersions of a supercell into the 1st BZ of the primitive cell [32][33][34][35][36][37].…”

Section: Resultsmentioning

confidence: 99%

How to resolve a phonon-associated property into contributions of basic phonon modes

Cheng¹,

Zhang²,

Liu³

2019

J. Phys. Mater.

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Many properties of materials are associated with phonons. To better understand the phonon-property relation, it is a common practice to decompose the phonon-associated property into the contributions of basic phonon/vibration modes (e.g. longitudinal/transverse acoustic/optical mode), and identify the mode(s) that dominate(s) the property. The existing methods rely on labelling the phonon into one of the basic modes (BMs), however, the vibration characteristics of many phonons are different from the definitions of BMs, indicating these methods may give wrong decomposition results. Here we present a new method based on treating the phonon as a mixture of the BMs. By aligning the wave vectors and then projecting the phonon eigenvector onto the eigenvectors of the BMs, we can obtain the weights of the BMs on the given phonon, which can be used to quantify the contribution of each BM to the property. As an example, we apply this method to unravel the phonon modes that dominate the scattering of the electrons at the conduction band edge in two-dimensional antimony, an emerging semiconductor that has attracted great interest for electronics, but its mobility-limiting factors remain unclear. We find that the electron scattering is dominated by the out-of-plane acoustic phonon mode followed by the longitudinal acoustic mode, which are different from the results of other methods. Our method is generally applicable to different kinds of phonon-related properties and to all crystal materials.

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Phonon Unfolding : A program for unfolding phonon dispersions of materials

Cited by 16 publications

References 49 publications

Phonon dispersion throughout the iron spin crossover in ferropericlase

Phonon dispersion throughout the iron spin crossover in ferropericlase

Alkali metal insertion into hard carbon – the full picture

How to resolve a phonon-associated property into contributions of basic phonon modes

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