First hyperpolarizability of polymethineimine with long-range corrected functionals

摘要

Using the long-range corrected (LC) density functional theory (DFT) scheme introduced by Iikura et al.[J.Chem.Phys.115,3540 (2001)] and the Coulomb-attenuating model (CAM-B3LYP) of Yanai et al.[Chem.Phys.Lett.393,51 (2004)],we have calculated the longitudinal dipole moments and static electronic first hyperpolarizabilities of increasingly long polymehtineimine oligomers.For comparison purposes Hartree-Fock (HF),M0ller-Plesset perturbation theory (MP2),and conventional pure and hybrid functionals have been considered as well.HF,generalized gradient approximation (GGA),and conventional hybrids provide too large dipole moments for long oligomers,while LC-DFT allows to reduce the discrepancy with respect to MP2 by a factor of 3.For the first hyperpolarizability,the incorrect evolution with the chain length predicted by HF is strongly worsened by BLYP,Perdew-Burke-Ernzerhof (PBE),and also by B3LYP and PBE0.On the reverse,LC-BLYP and LC-PBE hyperpolarizabilities are correctly predicted to be positive (but for the two smallest chains).Indeed,for medium and long oligomers LC hyperpolarizabilities are slightly smaller than MP2 hyperpolarizabilities,as it should be.CAM-B3LYP also strongly improves the B3LYP results,though a bit less impressively for small chain lengths.The present study demonstrates the efficiency of long-range DFT,even in very pathological cases.