On the accurate calculation of polarizabilities and second hyperpolarizabilities of polyacetylene oligomer chains using the CAM-B3LYP density functional

Abstract

The polarizability and second hyperpolarizability of polyacetylene oligomer chains of increasing size up to C(24)H(26) were investigated by means of the Coulomb-attenuating method (CAM-B3LYP) using response theory. It was found that this long-range corrected density functional removes to large parts the overestimation observed for standard methods and in many cases provides results close to those of coupled cluster calculations. A direct comparison to experimentally observed dynamic hyperpolarizabilities is made to estimate the accuracy of the method. A basis set study revealed a noticeable contribution of diffuse orbitals to the hyperpolarizability also for larger oligomers. Furthermore, CAM-B3LYP is also confirmed to provide molecular geometries close to experimentally observed structures, especially for longer chain lengths.

Evaluation of the nonlinear optical properties for an expanded porphyrin Hückel-Möbius aromaticity switch

“…37 It is well established that diffuse and polarization functions are required for a quantitative description of both the electronic and vibrational (hyper)polarizabilities of medium size organic molecules. 32,[38][39][40][41] Nevertheless, it has also been found in the past that the 6-31G basis set is adequate to obtain qualitative results, and many previous theoretical investigations of NLOP have used it. 31,36,39,40,42 In Tables II and III, one can see that the increment of basis set from 6-31G to 6-311G(d) does not provoke a large variation of α e and γ e values (lie in the 2%-32% range).…”

Stereoelectronic, Vibrational, and Environmental Contributions to Polarizabilities of Large Molecular Systems: A Feasible Anharmonic Protocol

“…This separation is denoted by the indices in the apex, the first one denoting the level of electric anharmonicity and the second one denoting the level of mechanical anharmonicity: 13,14 (3) The pure vibrational terms can be treated in a similar way obtaining explicit formulas that depend on the derivatives of the electric dipole moment, in addition to the cubic and quartic force constants. The total value is separated into a harmonic term and three anharmonic contributions which are distinguished according to their degree of mechanical and electric anharmonicity: (4) We compute these terms using the formulas obtained by Bishop et al [13][14][15][16] albeit with a slightly different expression for the [μ 2 ] 0,2 term, shown in the Appendix, since we found the original expression for this term reported in the literature to be incorrect. Anharmonic calculations tend to be very expensive for medium-large sized systems because they require the evaluation of force constants up to the fourth order, as well as high-order geometrical derivatives of the electronic properties under investigation.…”

“…Molecular cavities were built using a set of interlocking spheres centered on the atoms, with radii according to the Gaussian09 defaults. The solvents' static and optical dielectric constants used are ε = 2.27 and ε opt = 2.25 for benzene, ε = 2.23 and ε opt = 2.13 for CCl 4 , and ε 0 = 2.21 and ε opt = 2.02 for 1,4-dioxane. In the following tables we report the isotropic polarizabilities (the trace of the polarizability tensor divided by 3) α is , as well as the longitudinal component (along the molecular axis) α zz .…”

“…[1][2][3] In this context, the role of quantum mechanical approaches for complementing experimental studies is continuously increasing from both the point of view of the dimensions of the systems amenable to accurate computations, and of the inclusion of dynamic and environmental effects in addition to intrinsic stereoelectronic ones. Even pending further developments for specific shortcomings, lastgeneration density functionals are providing sufficiently reliable results for the nonlinear properties of isolated molecules at their equilibrium geometries 4 to warrant consideration of additional effects. As a matter of fact, a number of studies have demonstrated the importance of both vibrational and environmental contributions to (hyper)polarizabilities.…”

Choosing a density functional for static molecular polarizabilities

“…[4][5][6][7][8][9]. The purpose of this Letter is to report how well a comprehensive range of functionals, including recently proposed ones, predict the static mean electronic dipole polarizabilities (α) of molecules of interest in bioorganic and pharmaceutical chemistry.…”