A six-term truncated Fourier cosine series has been developed to model the torsional profile between the two thiophene rings of dithiophene. Preliminary work in the development of dithiophene potentials revealed a conformational dependence of the inter-ring bond and angles between the two rings with the force constant and the equilibrium length and angle as a function of the torsion angle. The form the function for the parameters of the inter-ring potentials is that of a six-term cosine series. When this dependence is accounted for, accurately models the torsional potential energy surface of dithiophene. The new model with the inter-ring potentials using the standard OPLS-aa format approximates the torsional potentials surface as well as the conformational-dependent model does, but with the added advantage of a less intensive implementation into standard molecular simulation software. Classical simulations have been conducted for dithiophene to verify the new parameter set developed from the quantum mechanical data. Follow-up work is extending this parameter set to alkyl substituted dithiophene with the long term goal of simulating poly(3-alkylthiophene) systems. Comparisons with experimental data were used to validate the new parameter sets.

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