First principle study of Lithium impurity effect on energy gap of trans-polyacetylene chain

In this work we have calculated the electronic states of the trans-polyacetylene (t-PA) molecule within the framework of Density Functional Theory (DFT). For this purpose we have used SIESTA code based on the DFT within the Local Density Approximation (LDA). Fully self-consistent Kohn-Sham functional was performed. We used the Ceperley-Alder (CA) form of the exchange-correlation Potential in LDA. Following the above procedures we have calculated Density of State (DOS) of doped t-PA chain. Our results show that, as expected, the energy gap has a considerable decrease with doping.