  Using NMTO-downfolding technique we have revisited the issue of relative
stability between zincblende (ZB) and wurtzite (WZ) symmetries in case of CdS,
CdSe and CdTe semiconductors. Our computed ionicity factors using accurate
NMTO-downfolding successfully brings out the right trend within the CdX series
- CdS being most ionic stabilizes in WZ symmetry while CdSe and CdTe being more
covalent stabilizes in ZB symmetry. Our NMTO constructed Wannier functions
corresponding to only valence bands provide a nice demonstration of this fact.
The tendency towards ZB stability is governed by the covalency which prefers
isotropic nature of the tetrahedral bonds.

Mesoscale and Nanoscale Physics;Materials Science