Ab-initio and density functional theory simulation for lactide monomer

Poly(L-lactide) is one of the polyesters that are widely used in fibrous, packaging and biomedical applications. The modeling in this work aimed to simulate the properties of the lactide monomer as well as the produced polymer with an emphasis on the properties that can be experimentally verified. Simulations were performed at electronic scale by implementing different methods that represent multiple levels of the theory. Comparing the simulation results with the experimental data obtained from X-ray single crystallography showed that low level methods such as Hartree-Fock (HF) were able to optimize and predict the geometry of molecules with accuracy higher than that obtained with density functional theory (DFT) methods which performed better in predicting the energy and the spectroscopic (IR and NMR) properties for the structures. Increasing the size of the basis sets with DFT did not show much improvement in the prediction accuracy beyond a certain limit and B3LYP/6-311+G(2d,p) method was found to be sufficient for the calculation.