  SN 2006jc is a peculiar supernova (SN), in which the formation of dust has
been confirmed at an early epoch of ~50 days after the explosion. We
investigate the possibility of such an earlier formation of dust grains in the
expanding ejecta of SN 2006jc, applying the Type Ib SN model that is developed
to reproduce the observed light curve. We find that the rapid decrease of the
gas temperature in SN 2006jc enables the condensation of C grains in the C-rich
layer at 40-60 days after the explosion, which is followed by the condensation
of silicate and oxide grains until ~200 days. The average radius of each grain
species is confined to be less than 0.01 micron due to the low gas density at
the condensation time. The calculated total dust mass reaches ~1.5 Msun, of
which C dust shares 0.7 Msun. On the other hand, based on the calculated dust
temperature, we show that the dust species and mass evaluated to reproduce the
spectral energy distribution observed by AKARI and MAGNUM at day 200 are
different from those obtained by the dust formation calculations; the dust
species contributing to the observed flux are hot C and FeS grains with masses
of $5.6 \times 10^{-4}$ Msun and $2.0 \times 10^{-3}$ Msun, respectively,
though we cannot defy the presence of a large amount of cold dust such as
silicate and oxide grains up to 0.5 Msun. One of the physical processes
responsible for the difference between calculated and evaluated masses of C and
FeS grains could be considered to be the destruction of small-sized clusters by
energetic photons and electrons prevailing within the ejecta at the earlier
epoch.
