Short range order and network connectivity in amorphous AsTe 3 : A first principles, machine learning and XRD study

The atomic scale structure of amorphous AsTe3is investigated through X-ray diffraction, first-principles molecular dynamics (FPMD), and machine learning interatomic potentials (ML-GAP) ob-tained by exploiting the ab-initio data. We obtain a good agreement between the measured andmodelled diffraction patterns. Our FPMD results show that As and Te obey the 8-N rule with anaverage coordination numbers of 3 and 2, respectively. We find that small fractions of under andover coordinated As and Te atoms occur in the amorphous phase with about 6% (FPMD), and 13%(ML-GAP) of 3-fold Te. As is found at the center of pyramidal structures predominantly linkedthrough Tenchains rather than rings. Despite the low As concentration in AsTe3, its local envi-ronment feature a very high chemical disorder that manifests through the occurrence of homopolarbonds including at least 57% of As atoms