Thermal conductivity of glassy GeTe₄by first-principles molecular dynamics

Abstract

A transient thermal regime is achieved in glassy GeTe by first-principles molecular dynamics following the recently proposed "approach-to-equilibrium" methodology. The temporal and spatial evolution of the temperature do comply with the time-dependent solution of the heat equation. We demonstrate that the time scales required to create the hot and the cold parts of the system and observe the resulting approach to equilibrium are accessible to first-principles molecular dynamics. Such a strategy provides the thermal conductivity from the characteristic decay time. We rationalize in detail the impact on the thermal conductivity of the initial temperature difference, the equilibration duration, and the main simulation features.

Interface thermal behavior in nanomaterials by thermal grating relaxation

“…We consider now the set of PBC, involving ITRs, in Eqs. (13), (14), (15), and (16). In the present non-local formulation, the heat flux reads…”

“…AEMD has been applied by several authors to the calculation of the thermal conductivity in c-Si,c-Ge and α-quartz [1], in Si/Ge nanocomposite [9], in Si nanowires [10] and in graphene-based structures [11,12]. Initially developed for classical Molecular Dynamics (MD) this technique has been recently implemented in ab-initio calculations as well [13].…”

Thermal conductivity and transport modes in glassy GeTe4 by first-principles molecular dynamics

“…However, given the high computational cost of the Green-Kubo [9] or direct methods [10], FPMD have to be combined with more tractable, alternative approaches. With this purpose in mind, we calculated via FPMD the thermal conductivity of a disordered material (glassy GeTe 4 ) [11] by taking advantage of the approach-to-equilibrium molecular dynamics (AEMD) methodology [12]. In this first joint application of FPMD and AEMD, we showed that the inherent time intervals are within the reach of FPMD, in spite of a substantial temporal relaxation from an out-ofequilibrium situation (phase 2 of AEMD) featuring two adjacent parts of a periodic volume kept at different temperatures (phase 1 of AEMD).…”

Nonequilibrium ab initio molecular-dynamics simulations of lattice thermal conductivity in irradiated glassy Ge2Sb2Te5

“…It is noted that controlled irradiation (with He ions) has been used to lower the lattice thermal conductivity of Si nanowires. 38 In a recent AEMD study for a related glassy chalcogenide material, namely GeTe 4 , the authors reported a value of 0.013±0.003 W K −1 m −1 for the thermal conductivity, 39 which is an order of magnitude lower than the experimental measurement for this material (0.1 W K −1 m −1 ). 40 This discrepancy is likely due to the small model system size (185 atoms), which illustrates the limitations of tractable ab initio molecular-dynamics simula-tions.…”

“…Non-equilibrium methods require careful consideration of finite-size effects and they can no longer be easily applied to materials with a higher thermal conductivity, or with a longer mean-free path, especially at low temperature. Nevertheless, long-wavelength modes and quantum effects are not significant in glassy Ge 2 Sb 2 Te 5 at 300 K. 8,39 While not a substitute for analysing the finite-size effects, the influence of the boundary-region Langevinthermostat damping time was included in our estimates of the lattice thermal conductivity and is discussed in the Supplemental Material.…”