: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Electric field poled organic electro-optic materials: state of the art and future prospects.

Organophosphorus π-Conjugated Materials

http://casey.brown.edu/chemistry/research/LSWang/publications/239.pdf

All-Boron Aromatic Clusters as Potential New Inorganic Ligands and Building Blocks in Chemistry

Organotransition metal complexes have much to offer as nonlinear optical (NLO) chromophores since they allow large hyperpolarizabilities to be combined with various other physical properties in an unparalleled diversity of molecular structures. This Account summarizes our synthetic chemistry driven investigations in the NLO research field, which have focused primarily on complexes of ruthenium, and to some extent iron. A number of fascinating discoveries are described, including the first demonstration of redox-induced switching of NLO behavior and chromophores which disobey the otherwise universal rule that elongation of polyene systems leads to continual increases in quadratic NLO responses.

Switchable nonlinear optical metallochromophores with pyridinium electron acceptor groups.

The electronic and vibrational contributions to the dipole moment, polarizabilities, and first hyperpolarizabilities of HArF are reported. These have been computed by using a series of systematically built basis sets and a hierarchy of computational methods. HArF has a very large first hyperpolarizability along the z axis. This has been rationalized by invoking the difference in the electronic structure between the ground and the first excited state. The argon fluorohydride has been recently derived and characterized. The present study provides complementary data for the understanding of the electronic structure of this interesting argon derivative.

The Dipole Moment, Polarizabilities, and First Hyperpolarizabilities of HArF. A Computational and Comparative Study

The relationship between nonlinear susceptibilities and hyperpolarizabilities defined using different conventions is reexamined. In previous work [Willetts et al., J. Chem. Phys. 97, 7590 (1992)], relations between different conventions for microscopic hyperpolarizabilities have been derived, but the application of the corresponding conversion factors led to several inconsistencies. It is shown that different conventions for macroscopic susceptibilities have to be taken into account, too, in order to arrive at consistently comparable values. The complete set of conversion factors between several conventions are given for second harmonic generation, electric field induced second harmonic (EFISH) generation, and third harmonic generation. As an illustration, experimental EFISH and hyper-Rayleigh scattering results of p-nitroaniline are compared with each other and with recent results of ab initio computations including solvation effects. Several problems in the comparison of computational and experimental values are also discussed.

Problems in the comparison of theoretical and experimental hyperpolarizabilities revisited.

Macroscopic first-, second-, and third-order susceptibilities of the urea crystal are calculated using static and frequency-dependent ab initio molecular (hyper)polarizabilities at the self-consistent field (SCF) and second-order-Mo/ller–Plesset (MP2) levels. Environmental effects are taken into account using a rigorous local-field theory and are compared with the anisotropic Lorentz field factor approximation. The electric field arising from the permanent dipoles of the surrounding molecules is explicitly taken into account using a self-consistent approach. The dipole moment and the first hyperpolarizability are particularly strongly dependent on this field, but the crystal structure leads to a fortuitous cancellation of the field effect on the second-order susceptibility. The experimental linear susceptibility is accurately reproduced, while differences remain for the quadratic susceptibility. Dispersion curves for the first-order susceptibility, and results for quadratic electrooptic effect (QEO), elec...

Calculation of macroscopic first-, second-, and third-order optical susceptibilities for the urea crystal

Calculation of macroscopic linear and nonlinear optical susceptibilities for the naphthalene, anthracene and meta-nitroaniline crystals

The electric field poling process of nonlinear optical chromophores embedded in an amorphous polymer matrix was studied using molecular dynamics (MD) simulations. Three systems were considered, consisting of a poly(methyl methacrylate) matrix doped with the following chromophores:  N,N-dimethyl-p-nitroaniline (DPNA), 4-(dimethylamino)-4‘-nitrostilbene (DMANS), and N,N‘-di-n-propyl-2,4-dinitro-1,5-diaminobenzene (DPDNDAB). The cooling process in the presence of a poling electric field was simulated at constant NPT conditions using simulated annealing. The rotational dynamics of the dopants was investigated in the unpoled and poled states above Tg and in the poled state below Tg. The short-time behavior with respect to the back-relaxation to the unpoled state following removal of the poling field was examined for the systems below Tg and was found to deviate from the single-exponential model. The electric field effects, during and following poling, were examined by computing the angle between the dipole mom...

Heribert Reis

Papers

The Dipole Moment, Polarizabilities, and First Hyperpolarizabilities of HArF. A Computational and Comparative Study

Problems in the comparison of theoretical and experimental hyperpolarizabilities revisited.

Calculation of macroscopic first-, second-, and third-order optical susceptibilities for the urea crystal

Calculation of macroscopic linear and nonlinear optical susceptibilities for the naphthalene, anthracene and meta-nitroaniline crystals

Molecular Dynamics Simulations of Electric Field Poled Nonlinear Optical Chromophores Incorporated in a Polymer Matrix