Loads Susi Lehtola's tabulated effective atomic charges Z_eff(r) from the OpenQP data file (basis_sets/sap_grasp.dat, generated offline by tools/sap/generate_sap_data.py from pyscf.dft.sap_data) and evaluates the SAP potential of a neutral atom, V_A(r) = -Z_eff(r) / r, by linear interpolation, matching the reference implementation (S. Lehtola, J. Chem. Theory Comput. 15, 1593 (2019)).