Four-phonon and normal scattering in 2D hexagonal structures

The Enormous and Distinctive Role of Four-Phonon Scattering in the Thermal Transport Characteristic of Pentagonal Structures

“…After comparing the phonon properties of graphene, BN, AlN, and GaN, it is found that in graphene, the 3ph scattering rate is greater than the 4ph scattering rate, but as the atomic mass ratio increases, the ratio of 4ph to 3ph scattering rates gradually exceeds 1 and continues to increase. 39 In contrast to the above results, some materials without phonon bandgaps also exhibit strong 4ph scattering processes, such as AgCrSe 2 , where the mechanism involves the relatively flat transverse acoustic branch caused by 4ph resonance, significantly inhibiting heat transfer. 40 Furthermore, studies also found that the 4ph scattering rates of some 2D materials with reflection symmetry structures may be remarkable.…”

“…Next, we analyze this phenomenon from the perspective of mechanism. According to the theory of 4ph processes, , in the low-frequency regime, the splitting process is constrained by the lack of quantum states available to accept the emitted phonons, thus making the probability of its occurrence relatively small due to the inability to satisfy energy conservation. Correspondingly, the probability of occurrence for the recombination process generally decreases as the frequency increases.…”

“…Additionally, a higher atomic mass ratio can trigger stronger 4ph scattering, and its mechanism is closely related to the phonon bandgap. After comparing the phonon properties of graphene, BN, AlN, and GaN, it is found that in graphene, the 3ph scattering rate is greater than the 4ph scattering rate, but as the atomic mass ratio increases, the ratio of 4ph to 3ph scattering rates gradually exceeds 1 and continues to increase . In contrast to the above results, some materials without phonon bandgaps also exhibit strong 4ph scattering processes, such as AgCrSe 2 , where the mechanism involves the relatively flat transverse acoustic branch caused by 4ph resonance, significantly inhibiting heat transfer .…”

Distinct anharmonic characteristics of phonon-driven lattice thermal conductivity and thermal expansion in bulk MoSe2 and WSe2

“…The effect of higher-ordered scattering processes and their temperature dependence was also observed in strongly anharmonic superionics and 2-d materials, including WS 2 and graphene, where the impact of higher-order anharmonicity on thermal conductivity is found to be significant. 71–79…”

Role of four-phonon processes in thermal conductivity of two-dimensional materials and thermal-transport enhancement arising from interconnected nanofiller networks in polymer/nanofiller composites

“…However, when 4 th order IFCs were computed using an atomic displacement of 0.03 Å, the thermal conductivity reduction at 300 K through 4 th order processes was only 62% relative to the 3 phonon case, contradicting the reported 94% reduction in ref. 39 above. The thermal conductivity values obtained by using 4 th -IFCs with an atomic displacement of 0.03 Å were in good agreement with results obtained from molecular dynamics simulations 41 over a wide temperature range.…”