To obtain all the coefficients of the e ij tensor, we utilize VASP's LCALCEPS-tag, in which e elc ij are calculated from the self-consistent response to a finite electric field and e ion ij are obtained from Born Effective Charges, force constant matrices, and internal strain tensors. In addition, we compute the e ij tensors using DFPT method, where we use the same optimized structures but cannot include van der Waals interaction as already described.