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The effect of atomic hydrogen adsorption on TiO 2 -terminated and SrO-terminated SrTiO 3 ͑001͒ surfaces is studied using density functional theory calculations. Several adsorption coverages ͑1/12, 1/6, 1/3, 1/2, 2/3, and 1 monolayer͒ are considered. It is found that the hydrogen adsorption shows site selectivity and causes remarkable surface distortion. Surface metallicity induced by the hydrogen adsorption is observed and revealed to be caused by the electron donation from hydrogen to the surface. Our results suggest a mechanism of hydrogen-induced degradation and hydrogen-sensitive I-V characteristics of SrTiO 3 -based devices.

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First-principles calculations are performed to predict structural, electric, magnetic, and magnetoelectric properties of hexagonal rare-earth ferrites (RFeO 3 ) under chemical and hydrostatic pressures. Decreasing the rare-earth ionic radius has two dramatic consequences: (i) an enhancement of the electrical polarization by a factor of 60% and (ii) a magnetic transition, which renders the systems (weakly) ferromagnetic. Moreover and unlike conventional ferroelectrics, the electrical polarization strengthens as a hydrostatic pressure is applied and increases in magnitude in any hexagonal rare-earth ferrites. Finally, applying a hydrostatic pressure in RFeO 3 having small or intermediate rare-earth ionic radius results in the sudden disappearance of a weak magnetization and of the linear magnetoelectric effect above some critical pressure. Origins of these striking effects are revealed.