Negatively charged hydrogen at oxygen-vacancy sites in BaTiO3: Density-functional calculation

Abstract

Native defects and oxygen and hydrogen-related defect complexes in CdTe: Density functional calculations J. Appl. Phys.With a specific focus on defects formed from H atoms and oxygen vacancies ͑V O ͒ in perovskite-type oxide, stability and stable valence states of complex defects formation processes within BaTiO 3 are studied by using first-principle density-functional theory calculations. In our findings, H atoms diffuse as protons ͑H + ͒ into interstitial sites in BaTiO 3 , whereas these atoms when trapped at centers of V O sites convert to negatively ionized states ͑H − ͒. We also find that H atom trapping at V O sites occurs only in n-type carrier-rich environments without carrier compensation of V O 2+ and H + . If carrier electrons are compensated, H + ions are excluded from V O 2+ sites due to the repulsive Coulomb potential existing between the H + ion and the positively charged V O 2+ site. Difficulties in the calculation of the diffusion-energy diagram for H atoms, involving essential changes in the stable valence states during the diffusion process, are discussed and a practical solution is presented.

Identification of hydrogen defects in SrTiO3by first-principles local vibration mode calculations

“…Many computational studies have been dedicated to the identification of proton sites in the crystal structures with four-fold coordinated O, e.g., zincblende, wurtzite, rutile and bixbyite [2,3,5,6]. For the perovskite structure, there are computational results on proton sites in some compounds, for e.g., BaTiO 3 [7] and BaZrO 3 [8]. However, the direct calculation details of H site in SrTiO 3 are limited which impedes further study of H migration.…”

Analysis of Memory Effect Induced by Hydrogen Annealing

“…3). Perovskite oxides have a characteristic that hydrogen ions are easily taken into the inside of the crystals [11,12]. Hydrogen ions taken into the inside of Bi-2212 may attack oxygen in BiO or CuO 2 layers in the Bi-2212 crystal, and, as a result, the Pt/Bi-2212/Pt structure becomes HRS due to reduction of carrier concentration or destruction of CuO 2 planes that mediate electric conduction of the Bi-2212.…”

The atomic structure of protons and hydrides in Sm1.92Ca0.08Sn2O7−δ pyrochlore from DFT calculations and FTIR spectroscopy

“…This is in accordance with previous assumptions and recent ab initio calculations. 33,34 Formally, H O is a hydride and thus, similar to an oxide, has two valence electrons and an ionic radius of ca. 1.4 Å .…”