Objective: Particle swarm optimization (PSO) algorithm has been clubbed with
two numerical methods viz., negative factor counting (NFC) technique and inverse
iteration method to investigate the electronic structures and properties of model
Method: Band structures of polyglycine, polyalanine and polythreonine obtained from abinitio
Hartree-Fock crystal orbital method using minimal basis (MB) set, double zeta (DZ) set
and quasi-particle (DZ+QP) set respectively have been used as input to obtain the electronic
properties of the model peptide sequences using the proposed computational procedure.
Results: The results obtained indicate threonine to have strong influence over properties in
comparison to alanine and glycine. Ternary sequences offer better electronic delocalization
to the chain in comparison to the binary combinations. Better electronic properties are
obtained with DZ basis set than with MB basis set. Also, it is found that with better electron
correlation, the fundamental band gap value decreases by 3-4 eV.
Conclusion: The density of states curves obtained using NFC technique is in good
agreement with the PSO results. In all, coupling PSO algorithm with the otherwise
computationally expensive quantum calculations not only fastens the process but also
brings out useful output worthy of experimental investigations.