THE SELECTION OF AB INITIO METHOD FOR POLYETHYLENE MOLECULE

Abstract

Polyethylene is the simplest vinylic polymer in structure. Polyethylene chains consist of hydrocarbon chains. The selection of calculation methods and basis sets is important part through an ab initio approach based on quantum mechanics principles. This aims of research to select the influence of basis set variations on the simulation results of polyethylene tetramer molecules. The six basis sets used were 6-31G*, 6-31G**, 6-31++G**, 6-311+G*, 6-311++G**, and cc-pVDZ. Molecular modeling was performed in the HyperChem software into four main parameters: geometric optimize such as bond length and bond angle, infrared (IR) spectrum, and nuclear magnetic resonance (NMR) spectrum. The selection was performed by calculating the Predicted Residual of Sum Squares (PRESS) between theoretical and experimental data. The results indicated that the 6-311++G** basis set was the most suitable basis set to use based on the smallest total PRESS value obtained. The PRESS value for bond lengths and bond angles was 6.047889479, the PRESS value for infrared spectra was 76110.2513, and the PRESS value for NMR spectra was 1.546474