Assessment of Conventional Density Functional Schemes for Computing the Polarizabilities and Hyperpolarizabilities of Conjugated Oligomers: An Ab Initio Investigation of Polyacetylene Chains

DFT schemes based on conventional and less conventional exchange-correlation (XC) functionals have been employed to determine the polarizability and second hyperpolarizability of π-conjugated polyacetylene chains. These functionals fail in one or more of several ways: (i) the correlation correction to α is either much too small or in the wrong direction, leading to an overestimate; (ii) γ is significantly overestimated; (iii) the chain length dependence is excessively large, particularly for γ and for the more alternant system; and (iv) the bond length alternation effects on γ are either underestimated or qualitatively incorrect. The poor results with the asymptotically correct van Leeuwen-Baerends XC potential show that the overestimations are not related to the asymptotic behavior of the potential. These failures are described in terms of the separate effects of the exchange and the correlation parts of the XC functionals. They are related to the short-sightedness of the XC potentials which are relatively insensitive to the polarization charge induced by the external electric field at the chain ends. © 1998 American Institute of Physics

Ab initio studies of the static electronic first hyperpolarizability of polysilanenitrile

cited By 6International audienceWe have carried out a thorough study of the methodology/basis set dependences in predicting first hyperpolarizability (β) for polysilanenitrile (PSN) by using various wavefunction and density-based methods. Correlations between β and the bond length alternation values (Δr) are explained. Comparisons were made between PSN and the isoelectronic and isovalent analogues, and both the similarities and the differences in the β value behavior in these three polymers are discussed by using the resonance structure theory. © 2005 Elsevier B.V. All rights reserved

Ab initio prediction of extremely large first hyperpolarizability of polyphosphaacetylene and polyphosphasilyne

cited By 8International audienceCalculations at MP2/6-31G(d) level predict a very large first hyperpolarizability (β) for two phosphorus-containing oligomers, namely, polyphosphaacetylene, -(PCH)n- and polyphosphasilyne, -(PSiH)n-, i.e., 212 777 and 90 811 a.u., respectively, at n = 16. These values are 5.3 and 2.3 times of that for the nitrogen analogue of polyphosphaacetylene, that is, polymethineimine. In striking contrast, polyborophosphene, -(PHBH)n-, is predicted to have extremely small β values, with a β/n value approaching zero at large n. The causes for the relative β values in these four series are discussed, in light of the bonding structure, the π bond strength, the size of the nuclei, and the degree of delocalization. © 2005 Elsevier B.V. All rights reserved