Effect of temperature on structural, dynamical, and electronic properties of Sc 2 Te 3 from first-principles calculations.

The compounds Sc 2 Te 3 and Sb 2 Te 3 have the same crystal structure. Ge-Sb-Te alloys are also the most common prototype phase change memory (PCM) compounds in the GeTe-Sb 2 Te 3 pseudo-binary combination. Recently, alloying Sc atoms into Sb 2 Te 3 has enabled sub-nanosecond switching in large conventional phase-change random access memory (PCRAM) devices. However, prior study on the electronic structure and dynamic properties of the Sc 2 Te 3 system is very limited. In this work, we investigate the effect of temperature on the structural, dynamic, and electronic properties of the Sc 2 Te 3 compound through ab initio molecular dynamics simulations. We show that the distorted-octahedral clusters are connected by four-fold rings even at higher temperatures. Moreover, our results clearly illustrate a liquid-to-glass transition temperature, which is between approximately 773 K and 950 K. The effect of temperature changes on the electronic properties of the system manifests as a metal-to-semiconductor transition. The band gap obtained using the mBJLDA functional is twice the value obtained using the PBE functional. Our studies provide useful insight into the local structure and dynamic and electronic properties of the Sc 2 Te 3 system at the atomic level. We hope that this work could stimulate more theoretical work on the development of cache-type phase-change memory and broaden its application in the field of PCM.