Nonlinear Optical Properties of Threefold Coordinated Paramagnetic Si Centers:  An ab Initio Time-Dependent Hartree−Fock Study on SiH₃ Radical

Abstract

Static and dynamic (hyper)polarizabilities of SiH3 radical have been calculated by ab initio time-dependent unrestricted Hartree−Fock method with the use of a double-ζ plus polarization basis set. In order to examine the effect of a Si dangling bond on the polarizabilities, calculations have also been performed on the diamagnetic SiH4 molecule using the same method and the basis set. A comparison of the polarizabilities of the two systems reveals that a dangling bond at the Si atom causes only a minor change in the value of polarizability, α. However, a Si-dangling bond in the case of SiH3 distorts the symmetry in the charge distribution in such a way that the dipole moment, μ, and the first-hyperpolarizability coefficient, β, become nonzero. The calculations also reveal that the contributions of the α-spin electrons and β-spin electrons to (hyper)polarizabilities of the SiH3 radical substantially differ from each other. The magnitude of hyperpolarizability coefficient is found to be determined by the contributions from different spins.

Interplay among Aromaticity, Magnetism, and Nonlinear Optical Response in All-Metal Aromatic Systems

“…A significant number of works highlight the variance of NLO response with a change in the spin multiplicity. , A detailed study of the NLO behavior in open-shell systems also displays the dependence of NLO response on the nature of the spin . We rationalize these observations by correlating NLO response with the spin density of any system.…”