INSTABILITIES IN CUBIC BABIO3 FROM TOTAL-ENERGY CALCULATIONS

Using local density functional theory and Bachelet-Hamann-Schlüter core potentials we have carried out total energy calculations for BaBiO3. Keeping first the ions at their ideal lattice positions we do not find any evidence for a local electronic instability in cubic BaBiO3 towards a modulated charge density. Performing calculations with frozen phonons at the R-point of the Brillouin zone we find that the breathing mode Γ′2 is stable whereas the [1 1 0]-component of the rotational mode Γ25 is unstable in the cubic structure. © 1990.