A comparative study of the effect of electron correlation in the hyperpolarizability of polyyne, polyacetylene and polypyrrole oligomers

Hartree–Fock static longitudinal (hyper)polarizability of polyyne

“…Preliminary results show that the effect of electron correlation is very large and can be accounted for by scaling the HF results presented here. 42,43 TABLE VI. Extrapolated values of ␥ L /N ͑in 10 4 a.u.͒ obtained from a least squares fit to Eq.…”

A large enhancement of (hyper)polarizabilities of polyyne capped by Cu

“…is appropriate to obtain the stable numerical values for all the molecules considered. Similar calculations were also carried out on the HC 2n H (n = 1-7) molecules for making more reasonable comparisons, despite the fact that there are many reports on the static a and c values of HC 2n H (n = 1-7) based on different theoretical methods [2,5,12,16,33,34]. At the present work, we focus on the longitudinal a and c (indicated by a L and c L , respectively) values which make significant contributions to the (hyper)polarizabilities of the linear p-conjugated molecule.…”

Application of the quasi-variational coupled cluster method to the nonlinear optical properties of model hydrogen systems

“…45,46 Due to the size and complexity of many of the systems of interest, ab initio calculations are typically applied to smaller representative test cases 24 or else resort to the investigation of model hydrogen chains as prototypical multiradicals 23,[47][48][49][50][51][52] in order to benchmark other, less expensive methods. 31,36,53,54 However, since the NLO properties are extremely sensitive to the treatment of electron correlation, 30,55,56 it has also become important to benchmark the ab initio methods amongst themselves on these systems. 32,37 For this purpose, it has become common to use traditional coupled cluster [57][58][59][60][61][62] (TCC) a) Electronic mail: KnowlesPJ@Cardiff.ac.uk.…”