  First-principle FLAPW-GGA band structure calculations are employed to obtain
the structural, electronic properties and chemical bonding picture for two
related layered phases, namely, quaternary oxyarsenides LaZnAsO and YZnAsO.
These compounds are found to be direct-transition type semiconductors with the
GGA gaps of about 0.65-1.30 eV. The peculiarities of chemical bonding in these
phases are investigated and discussed in comparison with quaternary oxyarsenide
LaFeAsO - a basic phase for the newly discovered 26-52K superconductors.
