STABLE POSITIONS OF A PROTON IN SC-DOPED SRTIO3 DETERMINED BY THE FIRST-PRINCIPLES PSEUDOPOTENTIAL CALCULATION

Stable positions of a proton in the protonic conductor Sc-doped SrTiO3 are obtained by a steepest-descents optimization of the ionic configu rations in the first-principles pseudopotential calculation. It is sho wn that, in a stable ionic configuration, a Ti (or Sc) ion moves away from the proton, while two O ions move towards the proton, from their positions in the ionic configuration of a perfect crystal SrTiO3, and that an O-H bond is formed, the length of which is about 1.03 Angstrom . The proton is located on the side opposite the Ti(Sc) ion with respe ct to a line connecting the two O ions, and the H-O-O angle is approxi mately 13 degrees.