Hydrogen impurity in yttria: Ab initio and μSR perspectives

E. L. Silva, A. G. Marinopoulos, R. C. Vilão, R. B. L. Vieira, H. V. Alberto, J. Piroto Duarte, and J. M. Gil
Phys. Rev. B 85, 165211 – Published 27 April 2012

Abstract

The incorporation of interstitial hydrogen in yttria was studied by means of ab initio calculations based on density-functional theory (DFT) and muonium spin polarization spectroscopy (μSR). The density-functional calculations, based on a semilocal functional within the GGA-PBE and a hybrid functional, uncovered multiple geometrical configurations for the neutral, H0, and the negatively charged, H, states of hydrogen, thus demonstrating the existence of metastable minimum-energy sites. It was observed that the low-energy configurations for H0 and H are similar: they prefer to relax in deep, interstitial sites, whereas the equilibrium configurations for the positively charged state, H+, were bond-type configurations with the hydrogen forming a covalent O-H bond with an O anion. For all neutral and negative configurations, localized defect levels were found inside the gap. Overall, the results for the formation energies obtained by the two different functionals are qualitatively similar; an amphoteric behavior was found for hydrogen after considering the lowest-energy structures for each charge state. The calculated acceptor transition level, obtained by the hybrid functional and seen near midgap, is consistent with μSR data from literature. The results are consistent with the present μSR data, where the observed diamagnetic signal is attributed to a donor-like muonium at the oxygen-bonded configurations and the paramagnetic signal to an acceptor-like deep muonium at the interstitial sites.

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  • Received 23 January 2012

DOI:https://doi.org/10.1103/PhysRevB.85.165211

©2012 American Physical Society

Authors & Affiliations

E. L. Silva* and A. G. Marinopoulos

  • Centro de Estudos de Materiais por Difracção de Raios-x (CEMDRX) and Center for Computational Physics, Department of Physics, University of Coimbra, P-3004-516 Coimbra, Portugal

R. C. Vilão, R. B. L. Vieira, H. V. Alberto, J. Piroto Duarte, and J. M. Gil

  • Centro de Estudos de Materiais por Difracção (CEMDRX) de Raios-x, Department of Physics, University of Coimbra, P-3004-516 Coimbra, Portugal

  • *elora@teor.fis.uc.pt
  • Also at: Escola Superior de Tecnologia da Saúde de Coimbra, Polytechnic Institute of Coimbra, P-3040-854 Coimbra, Portugal.

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Vol. 85, Iss. 16 — 15 April 2012

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