  The composition of planets is largely determined by the chemical and
dynamical evolution of the disk during planetesimal formation and growth. To
predict the diversity of exoplanet compositions, previous works modeled
planetesimal composition as the equilibrium chemical composition of a proto-
planetary disk at a single time. However, planetesimals form over an extended
period of time, during which, elements sequentially condense out of the gas as
the disk cools and are accreted onto planetesi- mals. To account for the
evolution of the disk during planetesimal formation, we couple models of disk
chemistry and dynamics with a prescription for planetesimal formation. We then
follow the growth of these planetesimals into terrestrial planets with N-body
simulations of late stage planet formation to evaluate the effect of sequential
condensation on the bulk composition of planets. We find that our model
produces results similar to those of earlier models for disks with C/O ratios
close to the solar value (0.54). However, in disks with C/O ratios greater than
0.8, carbon rich planetesimals form throughout a much larger radial range of
the disk. Furthermore, our model produces carbon rich planetesimals in disks
with C/O ratios as low as ~0.65, which is not possible in the static
equilibrium chemistry case. These results suggest that (1) there may be a large
population of short period carbon rich planets around moderately carbon
enhanced stars (0.65 < C/O < 0.8) and (2) carbon rich planets can form
throughout the terrestrial planet region around carbon rich stars (C/O > 0.8).
