  The antiferromagnetic (AF) model is generalized for the quasielectron system
composed of identical ionic-covalent dimers. The density-fluctuation and
covalent-correlation operators are constructed based on the extended AF density
matrices, and the quasielectron system is decomposed into 4-level subsystems
for the electron ionization and affinity. By considering the nearest-neighbor
hopping near the covalent limit, we can see the importance of the bonding
coefficients to the effective mass of the excited carrier in the crystal of the
zincblende structure.
