Interaction potentials nonlinear optical properties

In this paper, we make use of molecular modelling techniques, particularly the AMI semiempirical molecular orbital method, to study the intermolecular interactions that are important for determining the manner in which crystal formation takes place. We are particularly inter ested in compounds that can potentially exhibit nonlinear optical properties. The calculational techniques are directed towards providing insight into the manner in which the desired nonlinear optical properties can be op timized in the macromolecular crystal state.(1)... 

In addition, as far as electron-electron interaction is neglected, the tt electrons are subject to a potential with the full spatial symmetry of the CNT topology. The electronic wavefunctions can then be classified according to their transformation properties under the symmetry operations leaving the CNT invariant. As far as dipole approximation holds, both the linear and nonlinear optical response of a CNT are governed by matrix elements of the dipole operator between two electronic wavefunctions. Being the selection rules of dipole matrix elements essentially determined by the wavefunctions symmetry, it turns out that the optical properties of CNT are essentially rooted in their topology. 

Four calculations have been reported in related areas of molecule-field interactions. Evans (1982) has simulated the bulk anisotropy for a collection of molecules, which while dipolar were not polarizable nor based on the properties of a real molecule. The field-induced force was not explicitly defined in terms of a dipole-field interaction, rather a full Lennard-Jones potential was used. Coffey has examined the inertial relaxation of dipolar molecules in intense fields (Coffey et al., 1983). Madden has focused on interaction-induced effects in dielectric absorption (Tildesley and Madden, 1983) and transient nonlinear optical measurements in CS2 (Madden, 1987). Samios and Dorfmuller used a similar local field formalism to ours when they examined far IR absorption and utilized equilibrium fluctations to obtain correlation functions for liquid CS2 (Gburski et al., 1987). More details on these calculations... 

Au Au interactions also play a pivotal role in the photophysical characteristics of Au(i) alkynyl complexes. A red shift in the solid-state emission energies relative to that in solution is commonly observed for complexes with such interactions [87, 183, 188, 189]. In addition, the nonlinear optical (NLO) properties of a number of di- and trinuclear Au(i) alkynyl complexes with di- and tri-ethynylbenzene cores have been investigated by Humphrey and coworkers [191-194], These complexes may serve as potential NLO materials with reasonable first and second hyperpolarizabilities. Introduction of nitro group into these systems was suggested to enhance the optical nonlinearity. 

---