On the performance of DFT methods in (hyper)polarizability calculations: N4 (Td) as a test case

We present an extensive study of the electric (hyper)polarizabilities of N4 using conventional ab initio techniques, up to the couple cluster approach [CCSD(T)], and Density Functional Theory (DFT) methods. We evaluate the relative performance of the later by introducing graph theoretical arguments and pattern recognition techniques. This rigorous approach allows for a direct comparison which showed that the most similar/dissimilar DFT methods to CCSD(T) are the B3P86, mPW1PW91/B98LYP, respectively. The use of mPW1PW91 in the calculations of larger Nn clusters is encouraged because on the one hand reserves the effectiveness of DFT methods and on the other it is free of any parametrization.