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

Abstract

An analysis of thermal transients from non-equilibrium ab initio molecular-dynamics simulations can be used to calculate the thermal conductivity of materials with a short phonon mean-free path. We adapt the approach-to-equilibrium methodology to the three-dimensional case of a simulation that consists of a cubic core region at higher temperature approaching thermal equilibrium with a thermostatted boundary. This leads to estimates of the lattice thermal conductivity for the glassy state of the phase-change memory material, Ge 2 Sb 2 Te 5 , which are close to previously reported experimental measurements. Self-atom irradiation of the material, modelled using thermal spikes and stochastic-boundary conditions, results in glassy models with a significant reduction of diffusive thermal transport compared to the pristine glassy structure. This approach may prove to be useful in technological applications, e.g. for the suppression of thermal cross-talk in phasechange memory and data-storage devices.

Study of irradiation temperature effect on change of structural, optical, and strength properties of BeO ceramics when irradiated with Ar8+ and Xe22 heavy ions

“…As is known, when materials are heated, partial annealing and relaxation of defects occurs due to changes in the vibrational modes of atoms and subsequent annihilation of point defects with each other [23][24][25]. In this case, during the passage of heavy ions in the material, according to the theory of thermal peaks, regions with an increased temperature are formed along the trajectory of the ions, in which defects are formed [26][27][28][29][30]. Moreover, these regions have short lifetimes, but very high temperatures, which leads to the formation of a large number of mobile defects [28][29][30].…”

Thermal transport of amorphous phase change memory materials using population-coherence theory: a first-principles study

“…The phase changes are implemented by fast heating and cooling processes induced by applying an appropriate electrical current or laser pulse [2,5]. For PCM technology, the thermal transport properties of PCM materials will determine the switching time, cyclability, retention period, power consumption, and reliability of memory devices [6][7][8][9][10]. Therefore, it is crucial to quantitatively characterize the thermal conductivity of PCM materials, that is closely related to the heat transport phenomenon, and to dissect the influencing factors as well as underlying thermal transport mechanisms.…”

“…The time evolution of temperature difference in the studied system is monitored after a nonequilibrium initialization to predict thermal conductivity [27]. First-principles AEMD simulations have been employed to predict the thermal conductivities of amorphous GST [9,33] and GeTe 4 [34][35][36] and to analyze the size effect combined with an empirical model [33,36]. A significant temperature difference is indispensable for the AEMD method, so the temperature dependence of thermal conductivity was totally ignored.…”

“…A significant temperature difference is indispensable for the AEMD method, so the temperature dependence of thermal conductivity was totally ignored. The maximum temperature during the simulation even exceeded the crystallization temperature [9], which might cause the structural transition inevitably. Hence, more reliable simulation methods capable of considering the temperature dependence of thermal conductivity are still needed for amorphous PCM materials.…”