We provide a preliminary comparison of the basis set and functional dependence of OR calculations between isolate molecules and periodic systems. Specifically, we compare the isolated H 2 O 2 molecule at the geometry of the unit cell with 1D-periodic calculations as in the previous examples for two functionals: SVWN5 and HSE06, and three basis sets: aug-cc-pVTZ, cc-pVQZ, and augcc-pVQZ (in the following shortened to aTZ, QZ, and aQZ, respectively). A grid of 500 k points was used in the PBC calculations. To simplify the comparison, we focus on the isotropic OR (i.e., Tr(B)) rather than the whole tensor. The specific rotation values for all calculations are reported in Table of the SI. Here, we report relative % changes in OR calculated as: