ABSTRACT:The calculation of molecular hyperpolarizability, molecular frontier orbital energies of some donor-acceptor oxadiazoles (5a-f, 8a-f, and 9a-f) have been investigated using ab initio methods and different basis sets. Ab initio optimizations were performed at the Hartree-Fock (HF) and density functional (Beckee-3-Lee-YangParr; B3LYP) levels of theory with 6-31G basis set. The polarizability (Ͻ␣Ͼ), anisotropy of polarizability (⌬␣), and ground-state dipole moment (), first hyperpolarizability (), and molecular frontier orbital (HOMO, highest occupied molecular orbital and LUMO, lowest unoccupied molecular orbital) energies of 5a-f, 8a-f, and 9a-f have been calculated at the HF and B3LYP methods with 6-31G, 6-31G(d), 6-31ϩG(d), 6-31ϩϩG(d,p), 6-311G, 6-311G(d), 6-311ϩG(d), and 6-311ϩϩG(d,p) basis sets. Also, the molecular hardness () and electronegativity () parameters have been obtained using molecular frontier orbital energies. The Ͻ␣Ͼ, ⌬␣, , , HOMO, LUMO energies, and parameters have been investigated as dependence on the choice of method and basis set. The variation graphics of Ͻ␣Ͼ, ⌬␣, , , , and parameters using HF and B3LYP methods with different basis sets are presented. We have examined the frontier molecular orbital pictures of 5a-f, 8a-f, and 9a-f using B3LYP/6-31ϩϩG(d,p) level. The 5a-f, 8a-f, and 9a-f display significant linear, second-order molecular nonlinearity, and molecular parameters and provide the basis for future design of efficient nonlinear optical materials having the 1,3,4-oxadiazole core.