The cross sections (sigma(in) and sigma(el)) for low-energy (n) over b
ar interaction with various nuclei are calculated. The optical-cascade
model of slow-antineutron annihilation on nuclear targets is develope
d with the aim of using it as an event generator in experiment aimed a
t searches for n --> (n) over bar oscillations, A new limit on the per
iod of n --> (n) over bar oscillations in the vacuum is obtained from
the stability of O-16.