Hydrogen impurity in paratelluriteα-TeO2: Muon-spin rotation andab initiostudies

Abstract

We present a systematic study of isolated hydrogen in $\ensuremath{\alpha}$-TeO${}_{2}$ (paratellurite) by means of muon-spin spectroscopy measurements complemented by ab initio calculations based on density-functional theory (DFT). The observable metastable states accessible by means of the muon implantation allowed us to probe both the donor and the acceptor configurations of hydrogen, as well as to follow their dynamics. A shallow donor state with an ionization energy of 6 meV as well as a deep acceptor state are proposed, together with their atomic-level configurations and associated formation energies obtained from the DFT calculations. The latter show a tendency of interstitial hydrogen to bind strongly to bridging oxygen ions but also to coexist at sites deeper in the interior of the Te--O--Te rings with a more atomiclike character and a defect level in the gap. Atomlike interstitial muonium was observed; it has a hyperfine interaction of about 3.5 GHz. Charge and site changes with temperature are discussed.