Effects of Different Basis Sets and Donor-Acceptor Groups on Linear and Second-Order Nonlinear Optical Properties and Molecular Frontier Orbital Energies

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-Yang-Parr; B3LYP) levels of theory with 6-31G basis set. The polarizability (<alpha >), anisotropy of polarizability (Delta alpha), and ground-state dipole moment (mu), first hyperpolarizability (beta), 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), 6-31+G(d), 631++G(d,p), 6-311G, 6-311G(d), 6-311+G(d), and 6-311++G(d,p) basis sets. Also, the molecular hardness (eta) and electronegativity (chi) parameters have been obtained using molecular frontier orbital energies. The <alpha >, Delta alpha, mu, beta, HOMO, LUMO energies, eta and chi parameters have been investigated as dependence on the choice of method and basis set. The variation graphics of <alpha >, Delta alpha, mu, beta, eta, and chi 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/6-31++G(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. (C) 2009 Wiley Periodicals, Inc. Int J Quantum Chem 111: 130-147, 2011