J. Delhalle

Quantum chemistry aided design of organic polymers : an introduction to the quantum chemistry of polymers and its applications

This book is intended for those who are interested in understanding the electronic structure and properties of polymers. The scope of the book is to provide the non-specialist reader with a comprehensive and unified description: (i) of quantum mechanical methods, mainly originating from quantum chemistry, to calculate the electronic properties of polymers, (ii) of their use for interpreting and predicting results in fields where the electronic structure is playing an important role, like the electrical conductivity and the non linear optical properties of conjugated polymers.It will also serve as a reference book to lecture graduate students on the electronic structure of polymers or more generally of quasi-one dimensional materials. In this framework, it is worth stressing that the quantum theory of polymers bridges the gap between chemistry and physics. Since no book of this kind involving a strong interaction between theoretical and experimental concepts is available at the moment, it will also meet a need for a timely monograph in a field of important and fast growing interest.

Electronic structure of conducting polymers from heteroaromatic bicyclic compounds

Abstract A series of conjugated polymers based on indole and heteroaromatic bicyclic compounds ( X , Y = NH , S Se ) is obtained as thin films on gold or conducting glass electrodes, using controlled-potential electrochemical methods. Synthesized in an oxidized state, most of them can be reduced electrochemically, accompanied by a colour switching. X-ray photoelectron spectroscopy clearly shows the differences in electronic structure between the [2,3-b] and the [3,2-b] derivatives: two distinct redox states exist only when the conjugation pattern allows effective electron delocalization.

On the behaviour of exchange in restricted hartree-fock-roothaan calculations for periodic polymers

Abstract Analysis of the restricted Hartree-Fock (RHF) exchange potential is presented. In polymeric chains, a relation between the short-rangeness of the exchange and the energy gap is observed. In metallic systems, the exchange is of long-range and correlation corrections are expected to be important. The validity of RHF solutions in metallic situations is considered.

On the need for computing derivatives of energy bands in band structure caclulations

Abstract In view of recent misleading band structures of polymers, a general procedure is presented in order to compute derivatives of energy bands and get correct indexing and labelling of electronic band structures of regular polymers.

Electronic structure and nonlinear optical properties of aromatic polymers and their derivatives

Abstract We present the results of calculations on the electronic properties and electrical polarizabilities of polyaromatic and polyarylene vinylene systems. The n-doping of polyaromatics is shown to produce a marked polarizability increase due to both geometrical relaxation and charge transfer processes. Differences between p-type and n-type doping are stressed. The advantages of fused-ring and/or quinoid structures are illustrated. Thieno[3,4-c]thiophene oligomers are calculated to display extremely high polarizabilities. In polyarylene vinylenes, the combination of aromatic and vinylene moieties is found to lead to promising nonlinear optical characteristics.

Restricted hartree-fock investigation of the changes induced in the electronic structure of an infinite chain of hydrogen atoms when doping with lithium

Abstract A restricted Hartree—Fock study of the posible structural modifications of an infinite model chain under the effect of doping is presented It is shown that the tendency to bond alternation decreases with dopina and that there exists an optimal dopant concentration at which almost regular electron distribution is attained and the electrical energy gap is minimized.

Advantages of the Fourier space RHF band structure approach: Application to polyoxymethylene using a distributed basis set of s‐type Gaussian functions

In this contribution, we outline the Fourier space-restricted Hartree–Fock (FS–RHF) approach to the calculation of the band structure of polyoxymethylene (POM) using a distributed basis set of s-type Gaussian functions (DSGF) to simulate p-type functions. The band structure results are compared to those obtained using minimal STO-3G basis sets, within the conventional RHF direct space (DS) approach, and subminimal floating spherical Gaussian orbital (FSGO) basis sets. While the FSGO basis sets are unable to describe correctly the oxygen lone pairs and their interactions, the DSGF basis set reproduces qualitatively the features of the band structure observed with the minimal basis set. We show that minor differences between the FS and DS results originate in difficulties of lattice summations within the DS approach, illustrating the advantages of the FS method compared to the conventional DS approach.xa0© 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 1045–1054, 1998

Towards Specific AB Initio Programs for Polymer Calculations

Since the first theoretical workds of the sixties (1) on LCAO techniques in polymer quantum chemistry, the field has known a rapid development.

Density of electronic states in periodic and disordered chains of segmented polyacetylene

Abstract The density of valence one-electron states (DOVS) for different regular (periodic) and irregular models of segmented polyacetylene chains is computed with the Negative Factor Counting technique. To help in the interpretation of the evolution of the DOVS curves with the type of distribution in sp 3 defects, a comparison of the results is made with VEH calculations on regular infinite chains. A discussion on the interruption of conjugation introduced in polyacetylene by the sp 3 defects follows.

LCAO Methods for Band Structure Calculations of Polymers

The electronic structure of polymers has become in the last years a subject of great interest. Polymers as constituents of plastics are important from the point of view of structural materials; biopolymers play a fundamental role in life process and molecular crystals built up from polymers like (SN)X or the TTF-TCNQ system exhibit special physical characteristics. It is now hoped that more emphasis will be given to the synthesis of those polymers which present specific features.