First-Principles Study of the Phonon Lifetime and Low Lattice Thermal Conductivity of Monolayer γ-GeSe: A Comparative Study

Abstract

Germanium selenide (GeSe) is a unique two-dimensional (2D) material showing various polymorphs stable at ambient conditions. Recently, a new phase with a layered hexagonal lattice (γ-GeSe) was synthesized with ambient stability and extraordinary electronic conductivity, even higher than that of graphite, while its monolayer is semiconducting. In this work, using first-principles derived force constants and the Boltzmann transport theory, we explore the lattice thermal conductivity (κl) of monolayer γ-GeSe, together with a comparison with monolayer α-GeSe and β-GeSe. The κl of the γ-phase is relatively low (5.50 W/mK), comparable with those of α- and β-phases. The acoustic branches in α-GeSe are well separated from the optical branches, limiting scattering channels in the phase space, while for β-GeSe and γ-GeSe, the acoustic branches are resonant with the low-frequency optical branches, facilitating more phonon–phonon scattering. For γ-GeSe, the cumulative κl is isotropic and the phononic representative mean free path (rMFP) is the shortest (17.07 nm) among the three polymorphs, indicating that the κl of the γ-phase is less likely to be affected by the size of the sample, while for α-GeSe, the cumulative κl grows slowly with the mean free path and the rMFP is longer (up to 20.56 and 35.94 nm along zigzag and armchair directions, respectively), showing a stronger size dependence of κl. Our work suggests that GeSe polymorphs with overall low thermal conductivity are promising contenders for thermoelectric and thermal management applications.

Colossal figure of merit and compelling HER catalytic activity of holey graphyne

“…The phonon dispersion, thermal transport coefficients, and lattice thermal conductivity are calculated using the Hiphive 41 , BoltzTraP2 42 , and the ShengBTE 43 codes, respectively. This sophisticated method has been used to analyze the transport characteristics of numerous materials 44 – 46 . As inputs to ShengBTE, the 2nd and 3rd-order force constants are computed using a 3 × 3 × 1 supercell.…”

Unveiling the Distinctive Mechanical and Thermal Properties of γ-GeSe

“…Conversely, is proportional to when the optical phonon contribution to the thermal conduction is minimal. [33,62] Owing to these constraints, E and show a positive correlation across a broad spectrum of materials. This relationship follows the proportionality as depicted in Fig.…”

“…[27,29] Recent theoretical calculations have disclosed the low thermal conductivity ( ) of γ-GeSe, underscoring the crucial in uence of its unique bonding con guration on this aspect of the material. [30][31][32][33] However, a comprehensive experimental investigation into the mechanical and thermal properties linked to this distinctive bonding con guration in γ-GeSe is essential but remains unreported. The experimental con rmation of γ-GeSe's mechanical and thermal properties could pave the way for enhanced design and synthesis strategies, crucial for advancing thermoelectric and phase change memory technologies.…”

Effect of phonon anharmonicity on thermal conductivity of ZnTe Thin films

“…CsCl, CsBr, CsI), low-temperature anharmonicity has been observed, characterized by anharmonic displacements of the cesium ions and short phonon lifetimes [9,10]. For γ-GeSe, the cumulative thermal conductivity is isotropic and the phononic representative mean free path is the shortest (17.07 nm) among the three polymorphs, indicating that the thermal conductivity of the γ-phase is less likely to be affected by the size of the sample [11]. Pierre-François Lory et al achieved the direct quantitative measurement of phonon lifetimes in a single crystal of the clathrate Ba 7.81 Ge 40.67 Au 5.33 , renowned for its puzzling 'glasslike' thermal conductivity.…”