title: How fragility makes phase-change data storage robust: insights from ab initio simulations.
abstract: Phase-change materials are technologically important due to their manifold applications in data storage. Here we report on ab initio molecular dynamics simulations of crystallization of the phase change material Ag4In3Sb67Te26 (AIST). We show that, at high temperature, the observed crystal growth mechanisms and crystallization speed are in good agreement with experimental data. We provide an in-depth understanding of the crystallization mechanisms at the atomic level. At temperatures below 550 K, the computed growth velocities are much higher than those obtained from time-resolved reflectivity measurements, due to large deviations in the diffusion coefficients. As a consequence of the high fragility of AIST, experimental diffusivities display a dramatic increase in activation energies and prefactors at temperatures below 550 K. This property is essential to ensure fast crystallization at high temperature and a stable amorphous state at low temperature. On the other hand, no such change in the temperature dependence of the diffusivity is observed in our simulations, down to 450 K. We also attribute this different behavior to the fragility of the system, in combination with the very fast quenching times employed in the simulations.
authors.affiliation: 1] Institute for Theoretical Solid State Physics, RWTH Aachen University, 52056 Aachen, Germany [2] I. Physikalisches Institut (IA), RWTH Aachen University, 52056 Aachen, Germany.
authors.forename: Wei
authors.initials: W
authors.lastname: Zhang
authors.affiliation: Institute for Theoretical Solid State Physics, RWTH Aachen University, 52056 Aachen, Germany.
authors.forename: Ider
authors.initials: I
authors.lastname: Ronneberger
authors.affiliation: 1] I. Physikalisches Institut (IA), RWTH Aachen University, 52056 Aachen, Germany [2] Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA.
authors.forename: Peter
authors.initials: P
authors.lastname: Zalden
authors.affiliation: I. Physikalisches Institut (IA), RWTH Aachen University, 52056 Aachen, Germany.
authors.forename: Ming
authors.initials: M
authors.lastname: Xu
authors.affiliation: I. Physikalisches Institut (IA), RWTH Aachen University, 52056 Aachen, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Salinga
authors.affiliation: 1] I. Physikalisches Institut (IA), RWTH Aachen University, 52056 Aachen, Germany [2] JARA-FIT and JARA-HPC, RWTH Aachen University, 52056 Aachen, Germany.
authors.forename: Matthias
authors.initials: M
authors.lastname: Wuttig
authors.affiliation: 1] Institute for Theoretical Solid State Physics, RWTH Aachen University, 52056 Aachen, Germany [2] JARA-FIT and JARA-HPC, RWTH Aachen University, 52056 Aachen, Germany.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Mazzarello