  We report a collection of lowest-energy structures of hydrocarbon molecules
C_{m}H_{n} (m=1-18; n=0-2m+2). The structures are examined within a wide
hydrogen chemical potential range. The genetic algorithm combined with
Brenner's empirical potential is applied for the search. The resultant
low-energy structures are further studied by ab initio quantum chemical
calculations. The lowest-energy structures are presented with several
additional low-energy structures for comparison. The results are expected to
provide useful information for some unresolved astronomical spectra and the
nucleation of growth of nano-diamond film.
