  We advance the algorithm for ab initio calculations of Raman spectra for
large systems via applying external electric field, and complement it by a code
implementation we name RASCBEC. With the RASCBEC code, we have successfully
benchmark crystalline materials and compute Raman spectra of large molecules,
and amorphous oxides. Our results demonstrate a remarkable level of agreement
with the results from other commonly used codes as well as the experimental
data. The electric field approach for Raman spectra calculation is designed to
overcome the computational challenges associated with the conventional
approach, which requires the calculation of the macroscopic dielectric tensor
at numerous molecular geometries. The key innovation in our approach lies in
obtaining the first-order derivatives with respect to the external electric
field directly from VASP (the Vienna Ab Initio Simulation Package), as the Born
Effective Charge (BEC). The RASCBEC code not only significantly reduces
computational time, up to a factor of $N/8$, compared to the conventional
approach, where $N$ is the total count of atoms within the simulation box. But
also maintains the same level of accuracy, employing first-order numerical
derivatives that avoid the numerical noise associated with algorithms requiring
second-order derivatives, as seen in other electric field-based methods. This
advantage makes RASCBEC particularly beneficial for large molecules and
expansive amorphous systems.
