Non-nominal value of the dynamical effective charge in alkaline-earth oxides

M. Posternak, A. Baldereschi, H. Krakauer, R. Resta
1997 Physical Review B (Condensed Matter)  
We calculate ab-initio the electronic states and the Born dynamical charge Z* of the alkaline-earth oxides in the local-density approximation. We investigate the trend of increasing Z* values through the series, using band-by-band decompositions and computational experiments performed on fake materials with artificially-modified covalence. The deviations of Z* from the nominal value 2 are due to the increasing interaction between O 2p orbitals and unoccupied cation d states. We also explain the
more » ... variations, along the series, of the individual contributions to Z* arising from the occupied band manifolds.
doi:10.1103/physrevb.55.r15983 fatcat:boug332qczbanhp3bcw5vbawyi