Anharmonic lattice dynamics of superionic lithium nitride

Krenzer, Gabriel; Kim, Chang-Eun; Tolborg, Kasper; Morgan, Benjamin; Walsh, Aron

doi:10.1039/d1ta07631k

Cited by 13 publications

(25 citation statements)

References 69 publications

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“…It is not surprising that such large Grüneisen parameters exist since anharmonic vibrations have been linked to ion conducting materials. [ 4,5,9,50 ]…”

Section: Resultsmentioning

confidence: 99%

“…It is not surprising that such large Grüneisen parameters exist since anharmonic vibrations have been linked to ion conducting materials. [4,5,9,50] Having assessed the vibrational character of phonon modes, i.e., phonon-gas-or diffuson-like, from thermal transport behavior, it is also possible to characterize the vibrational character directly from the mode eigenvectors. In addition to having a frequency, each phonon mode has an eigenvector that defines the vibration direction of each atom in the material as well as the relative participation of each atom in the phonon mode.…”

Section: Diffuson-mediated Thermal Transportmentioning

confidence: 99%

“…[4,5] The influence of ionic motion on thermal transport has been discussed in the context of classic phonon-gas transport, where heat transport by phonons is thought to occur in a propagating manner on a length-scale much larger than interatomic distances (phonon-gas model, Figure 1, left). [7,8] Here, it is suggested that the scattering of propagating phonon quasiparticles can be increased by (static and dynamic) point-defects, the inherent anharmonicity associated with ionic jumps, [4,9] and the increased configurational complexity of the material, e.g., the atomic arrangement and distribution throughout the lattice (shown schematically in Figure 1). [4,5,10,11] This phonon-gas like thermal transport is commonly observed in structurally simple and crystalline thermoelectric materials like PbTe.…”

mentioning

confidence: 99%

“…[16] Fast ion transport has also been associated with diffuson-like signatures in inelastic neutron scattering experiments and ab initio molecular dynamics calculations. [4,9] As complexity, anharmonicity, and fast ion transport, are commonly found in both state-of-the-art solid electrolytes for battery applications, e.g., Na 3 PS 4 and Li 6 PS 5 Cl, [19][20][21] and promising thermoelectric materials such as Ag 9 GaSe 6 , Cu 2 Se and (Ag,Cu)CrSe 2 , [1,4,5,10,20,[22][23][24] there is an outstanding question if diffusons play a significant role in their thermal conductivity. In fact, many Ag + and Cu + conducting argyrodites have thermal conductivities below the theoretical "minimum" thermal conductivity proposed for purely propagating transport, [10,11,25,26] which may be explained…”

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confidence: 99%

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Considering the Role of Ion Transport in Diffuson‐Dominated Thermal Conductivity

Bernges

Hanus

Wankmiller

et al. 2022

Advanced Energy Materials

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Next‐generation thermal management requires the development of low lattice thermal conductivity materials, as observed in ionic conductors. For example, thermoelectric efficiency is increased when thermal conductivity is decreased. Detrimentally, high ionic conductivity leads to thermoelectric device degradation. Battery safety and design also require an understanding of thermal transport in ionic conductors. Ion mobility, structural complexity, and anharmonicity have been used to explain the thermal transport properties of ionic conductors. However, thermal and ionic transport are rarely discussed in direct comparison. Herein, the ionic conductivity of Ag+ argyrodites is found to change by orders of magnitude without altering the thermal conductivity. Thermal conductivity measurements and two‐channel lattice dynamics modeling reveal that the majority of Ag+ vibrations have a non‐propagating diffuson‐like character, similar to amorphous materials. It is found that high ionic mobility is not a requirement for diffuson‐mediated transport. Instead, the same bonding and structural traits that can lead to fast ionic conduction also lead to diffuson‐mediated transport. Bridging the fields of solid‐state ionics and thermal transport, it is proposed that a vibrational perspective can lead to new design strategies for functional ionic conducting materials. As a first step, the authors relate the so‐called Meyer–Neldel behavior in ionic conductors to phonon occupations.

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“…It is not surprising that such large Grüneisen parameters exist since anharmonic vibrations have been linked to ion conducting materials. [ 4,5,9,50 ]…”

Section: Resultsmentioning

confidence: 99%

Section: Diffuson-mediated Thermal Transportmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 2 more Smart Citations

Considering the Role of Ion Transport in Diffuson‐Dominated Thermal Conductivity

Bernges

Hanus

Wankmiller

et al. 2022

Advanced Energy Materials

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“…25 The temperature dependence of average phonon occupations is also likely a factor. 26,48 Nevertheless, Eqs. 5 and 6 provide new insights for understanding ion transport from a phonon perspective, as well as a starting point for continued investigations of isotope effects in Li + conductors.…”

Section: Figure 4 Vibrational Origin Of the Isotope Effect On Activat...mentioning

confidence: 99%

Relating critical phonon occupation to activation barrier in fast lithium-ion conductors

Agne

Frerichs

Wang

et al. 2022

Preprint

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Phonon-based (vibrational) theories of ion transport are likely key to developing new design strategies for solid-state ionic conductors. However, they are not often utilized because it is difficult to ascertain which vibrational frequencies are important, even in describing fundamental parameters such as the activation barrier. This is perpetuated by the fact that it is difficult to tune vibrational frequencies directly, without changing the chemical structure, in order to study underlying phonon relations. Using isotopic substitution of 6Li for 7Li, we are able to change the mobile ion vibrations in the two exemplary ion conductors Li10SnP2S12 and Li6PS5Cl without altering their structure. Using a combination of nuclear magnetic resonance spectroscopy and ab initio molecular dynamics simulations to characterize temperature-dependent ion transport, it is demonstrated that the isotopic substitution of 6Li for 7Li increases the activation barrier for Li-ion transport. The magnitude of this isotope effect cannot be explained by changes in the zero-point vibrational energy alone. Therefore, we propose that the observed change in the activation barrier is related to the differences in the average critical phonon occupation needed to overcome the activation barrier. Our hypothesis is supported by an analytical model, based on the physics of quantum harmonic oscillators, that gives good agreement with the experimental results. Thus, isotopic substitution provides unique insights into the vibrational perspective and frequency dependence of the activation barrier in fast Li-ion conductors.

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Renewing Fundamental Understanding of Ionic Transport in Inorganic Crystalline Solid‐State Electrolytes from the Perspective of Lattice Dynamics

Song,

Lin,

Wang

et al. 2024

Advanced Energy Materials

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Lattice dynamics has been widely employed to study various properties of crystalline materials, by revealing the atomic vibration rules with phonon dispersion curves. Modulating lattice‐dynamics‐related factors is an emerging trend in the design of inorganic crystalline solid‐state electrolytes (ICSSEs) with promoted ionic conductivity. Nevertheless, due to complicated interplay of these enormous factors, fundamental understanding of lattice‐dynamics‐influenced ionic transport is still limited. In this review, all related factors are classified into lattice static and dynamic ones based on their variability in ionic transport process, facilitating a methodological evaluation of their individual and interrelated influences. The previous efforts are affirmed to design ICSSEs by constructing potential energy surfaces for ionic transport based on lattice static factors (e.g., ionic arrangement, time‐scale dependent ionic concentration, and lattice softening). As for lattice dynamic factors, the possibility to quantify ionic transport activation energy and to screen the type of migration ions by phonon frequency and amplitude, respectively is validated. Specifically, it is highlighted that the optimization of specific phonon mode and the coupling of both lattice static and dynamic factors are essential to achieve superior ionic transport in ICSSEs. Finally, challenges and opportunities are pointed out in this field, which can potentially guide the future development of ICSSEs.

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Anharmonic lattice dynamics of superionic lithium nitride

Abstract: Superionic crystals reach an ionic conductivity comparable to liquid electrolytes following a superionic transition at high temperature. The physical mechanisms that lead to this behaviour remain poorly understood. It has...

Cited by 13 publications

References 69 publications

Considering the Role of Ion Transport in Diffuson‐Dominated Thermal Conductivity

Considering the Role of Ion Transport in Diffuson‐Dominated Thermal Conductivity

Relating critical phonon occupation to activation barrier in fast lithium-ion conductors

Renewing Fundamental Understanding of Ionic Transport in Inorganic Crystalline Solid‐State Electrolytes from the Perspective of Lattice Dynamics

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