As the real trans-polyacetylene molecule has finite chain length

its chain-terminal effects on various properties should be taken into account

that is to say

the aperiodic boundary condition should be employed in studying the properties of conducting polymers．However

if trans-polyacetylene chain is long enough

the chain-terminal effects can be ignored．In this paper

a one-dimensional finite compound lattice model of trans-polyacetylene chain is adopted．With considering the chain-terminal effects and the next-neighbor hopping interactions

the energy spectra and the density of states are calculated for trans-polyacetylene chains with the lattice number N from 10 to 200 under the periodic and aperiodic boundary conditions. The effects of chain length and interaction parameter on density of states and band width are also discussed．It is shown that the curves of DOS are symmetrical when the nearest-neighbor hopping is merely considered

and the valence and conduction bands are unsymmetrical when the next-neighbor term is taken into account．At the same time

some results under two kinds of boundary conditions are compared．When N＜50

the surface states appear under the aperiodic boundary condition

as well as DOS nearby the Feimi surface is larger than that under the periodic boundary condition．When N≥50

the surface states are difficult to distinguish between the valence and conduction bands

and DOS tends to be identical under two kinds of boundary conditions．Moreover

with N increasing

the difference of ionization energy under the two boundary conditions is reduced for the same parameter．In conclusion

when N＜50

there is a large difference for nearest-neighbor hopping and next-neighbor hopping due to the chain-terminal effect．This indicates that the aperiodic boundary condition plays an important role in dealing with finite systems．However

when N≥50

since the chain-terminal effect can be neglected

the periodic boundary condition is suitable for the finite trans-polyacetylene system．