To build an amorphous PET material, we used CHARMM 31 to arrange an 18 × 13 array of PET polymer composed by 9-mer chains spaced laterally and vertically to fill a box of 100 Å × 108 Å × 52 Å. CGenFF parameters were used to build the crystal PET chain topology and terminal methylation at both ends of each chain. In total, our simulation box had 234 PET polymer chains. The energy of the system was minimized via 500 steps of steepest descent minimization followed by 500 steps of adopted-basis Newton-Raphson minimization.