Abstract
The static linear and nonlinear optical properties of the σ-conjugated polymer α-t-Bu-ω-CN-poly(methylphenyl)silane (PMS) are studied at the Coupled-Perturbed Hartree-Fock (CPHF) level with 6-31+G(d) basis set. The calculated results reveal that the static first hyperpolarizabilities of this system increase with the main chain length and have a good agreement with experiments. The (hyper)polarizabilities per unit cell have been extrapolated to infinite chain limit and a comparison is made to those of polysilane and polyacetylene (PA). Besides, other structural properties depending on the σ-conjugated Si–Si skeleton length are investigated as well. Electron correlation effect is estimated and it turns out that the MP2 static first hyperpolarizability is about times larger than the corresponding CPHF value for the polymer with .
Highlights
In recent years, polysilanes have attracted increasingly extensive attention due to their unique physical and chemical properties resulting from σ-electrons delocalized along the silicon backbone
They have resulted in a variety of technological applications, such as conductor and semiconductor [1], photoconductive materials [2], organic multilayer, light emitting diodes (LEDs) [3], high-density optical data storage materials [4], electro luminescence (EL) devices [5, 6], and nonlinear optical (NLO) materials [7, 8]
One can deduce that the Si–Si bond dissociation energies are getting smaller and smaller; the σ-σ∗ transitions become easier as the Si skeleton length increases
Summary
Polysilanes have attracted increasingly extensive attention due to their unique physical and chemical properties resulting from σ-electrons delocalized along the silicon backbone. In this regard, they have resulted in a variety of technological applications, such as conductor and semiconductor [1], photoconductive materials [2], organic multilayer, light emitting diodes (LEDs) [3], high-density optical data storage materials [4], electro luminescence (EL) devices [5, 6], and nonlinear optical (NLO) materials [7, 8]. The mechanism of the variation of the static (hyper)polarizability as a function of chain length is elucidated by analyzing the Si–Si bond lengths and natural population analysis (NPA) charges on Si atoms along the backbone as well as energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO)
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