J. Waite

The polarizability and second hyperpolarizability of some azabenzenes

The average polarizability and second hyperpolarizability of some azabenzenes are reported and interpreted. A rule allowing the development of basis sets for complex molecules from those of appropriately defined fragments or models of them has been proposed and successfully tested.

Calculations of induced moments in large molecules. The average polarisability and second hyperpolarisability of some polyacetylenes and a scale of polarisation for CH3, F, H and NH2. A comparative study

The average polarisability, α, and second hyperpolarisability, γ, of H2(C2)n, where n= 1–8, are reported. The dipole interaction theory has been invoked for the rationalisation of these results. The effective polarisabilities and hyperpolarisabilities of CH3, F and NH2 with respect to H have been investigated in some acetylene and diacetylene derivatives. The established order for the effective polarisabilities is F < H < NH2 < CH3, while F < H < CH3 < NH2 has been found for the effective second hyperpolarisabilities. The proposed relationships have been confirmed in a further series of molecules representative of substituted alkanes, alkenes and arenes. The computations have been performed by employing the CHF–PT–EB–CNDO method, the reliability of which is well established.

Calculations of induced moments in large molecules. V. A study of intermolecular interactions and a functional group analysis of some amides, through the investigation of their polarizabilities and hyperpolarizabilities. A comparative study

The calculated polarizabilities α and hyperpolarizabilities γ of some amides are reported. The effect on these properties of methylation, bonding and nonbonding interactions, and isomerism, has been analyzed. Some aggregates of formamide have been considered and the cooperative character of the intermolecular interactions is demonstrated. The effective properties (α and γ) of several functional groups, associated with the examined amides, were studied using an appropriate index. The established order for the relative polarizabilities of the considered functional groups is: NH2OC<HCH3N<(CH3)2N<NHCH3OC<N(CH3)2OC while the relative hyperpolarizabilities follow the order: HCH3N<(CH3)2N<NH2OC<NHCH3OC<N(CH3)2OC. The computations have been performed by employing the CHF‐PT‐EB‐CNDO method. This procedure gave, for the considered amides, polarizability values which are in satisfactory agreement with experimental data (theoretical and experimental values differ on average by 9.4%).

The variation of calculated electric polarisabilities and hyperpolarisabilities, in cycloocta-1,5-diene, annulene, their anions and several of their derivatives, induced by changes in molecular structure and charge: a comparative study

Abstract The CHF-PT-EB-CNDO method has been used to calculate the induced change in polarisabilities and hyperpolarisabilities by changes of the charge and structure in C9H12 (the methylene bridged derivative of cycloocta-1,5-diene), C9H11−, C9H102−, C9H122−, several of their fragments, C10H12 (annulene), C10H122− and some of their derivatives. The contribution of various fragments to the properties has been investigated. The importance of the “through-bond” interaction has been shown. The bridge-induced polarisation in C9H102− is found to be the predominant contribution to this anions large linearity and nonlinearities. Computations using several derivatives of C10H122− have confirmed the large polarising effect of a bridge on the charge cloud of the resulting molecule. Delocalization of this charge cloud has been shown to lead to low linearities and nonlinearities in comparison with those which are associated with less extensive delocalization.

Analysis of some significant processes for molecular polarization

The polarisability, the first and second hyperpolarisabilities of NH2—C6H4—CnHn—CHC5H4, where n= 2, 4 and 6, as well as of some related compounds are reported. The effects of isomerism, conjugation and charge-transfer on the properties are discussed. In addition the influence of increasing the length of the conjugation path on the linear and non-linear electric properties has been commented upon. The properties have been computed using an extended-basis CNDO wavefunction and the coupled Hartree–Fock perturbation theory of McWeeney et al. The employed basis sets have been shown to give polarisability (α) and second hyperpolarisability (γ) values, for some fragments of the considered molecules, in reasonable agreement with the experimental results.

The polarisability and second hyperpolarisability of some biomolecules

Abstract The polarisability, α, and second hyperpolarisability, γ, of several molecules of biological interest (imidazole, cytosine, adenine, purine, guanine, etc.) are presented and analysed. The components of α and γ have been computed by employing the CHF-PT-EB-CNDO method which relies on (i) a CNDO wave function formed from a properly optimized, extended basis (EB) set and (ii) a coupled Hartree-Fock perturbation theory (CHF-PT) which was developed by McWeeny and co-workers.

On the many-body contributions to the interaction polarisability and hyperpolarisability of Hen

The many-body contributions to the interaction polarisability and hyperpolarisability of Hen (n=3,4, 5), for various configurations and distances have been determined and analysed. Several cases have been found where the three-body terms contribute more than 20% to Δα or Δγ of Hen. The remarkable dependence of the above interaction properties on the internuclear distances and the shape of the cluster has been demonstrated. The interaction hyperpolarisabilities are shown to be uniquely sensitive probes of the electronic structure changes induced by variation of the cluster configuration. The results were computed by employing a computational procedure which relies on anab initio wave function, McWeenys et al. coupled Hartree-Fock perturbation theory and an efficient algorithm for the determination of hyperpolarisabilities starting from a non-orthogonal basis set. The function counterpoise method has been used to reduce the basis set superposition error.

On the hyperpolarisabilities of some alkylbenzenes

The first and second hyperpolarisabilities of 12 methylbenzenes and five methyl derivatives of t-butylbenzene have been computed by employing the CHF-PT-EB-CNDO method. The effect of isomerism on these properties is discussed and a model has been defined to estimate and analyse the contribution to the second hyperpolarisability, γ, due to intramolecular interactions (between the substituents and the ring).

The Polarizability and Second Hyperpolarizability of the Phenyl Cation

The polarizability, α, and second hyperpolarizability, γ, of the phenyl cation are computed by employing the CHF-PT-EB-CNDO method. Variations of the properties induced by changes in the structure of the cation are discussed.