The first hyperpolarizability of p-nitroaniline in 1,4-dioxane: A quantum mechanical/molecular mechanics study

Abstract

In this work we have investigated the first hyperpolarizability of pNA in 1,4-dioxane solution using a quantum mechanics/molecular mechanics (QM/MM) model. The particular model adopted is the recently developed discrete solvent reaction field (DRF) model. The DRF model is a polarizable QM/MM model in which the QM part is treated using time-dependent density-functional theory and local-field effects are incorporated. This allows for direct computation of molecular effective properties which can be compared with experimental results. The solvation shift for the first hyperpolarizability is calculated to be 30% which is in good agreement with the experimental results. However, the calculated values, both in the gas phase and in solution, are by a factor of 2 larger than the experimental ones. This is in contrast to the calculation of the first hyperpolarizability for several small molecules in the gas phase where fair agreement is found with experimental. The inclusion of local-field effects in the calculations was found to be crucial and neglecting them led to results which are significantly larger. To test the DRF model the refractive index of liquid 1,4-dioxane was also calculated and found to be in good agreement with experiment.

Concomitant Effects of Transition Metal Chelation and Solvent Polarity on the First Molecular Hyperpolarizability of 4-Methoxyacetophenone Thiosemicarbazone: A DFT Study

“…For instance, the tot value for L1 is 7.298 × 10 −30 esu in gas-phase and 19.282 × 10 −30 esu in DMSO, while that for L2 is 11.079 × 10 −30 esu in gas-phase and 24.945 × 10 −30 esu in DMSO. The gas-phase tot values of the thione-thiol tautomers of MAPTSC are approximately 0.92-1.40 times larger than that of para-nitroaniline (7.9 × 10 −30 esu [35]), a prototype push-pull molecule [36], and about 19.57-29.71 times larger than that of urea (372.89 ×10 −33 esu [37]), indicating that MAPTSC is a potent NLO material. From the tot values of the thione-thiol tautomers of MAPTSC, it is clear that the second-order NLO response of MAPTSC is potentially switchable especially in polar solvents, due to the presence of a tautomeric form (thiol form) with a higher CT capability.…”

A joint theoretical and experimental study for elastic electron scattering from 1,4-dioxane

“…21 and that for 1,4-dioxane being ∼58.79 a.u. 22 Similarly, as a consequence of their very high symmetry (see. Fig.…”

Positron scattering from the cyclic ethers oxirane, 1,4-dioxane, and tetrahydropyran

“…25 We therefore do not repeat those details here, except for noting that a tungsten moderator of thickness 1 μm (Ref. 26) was employed in conjunction with a radioactive 22 Na isotope (current activity ∼1.6 mCi) and some electrostatic optics in order to produce the positron beam. Note that it is a standard practice in our laboratory, as a check for the validity of our techniques and procedures, to carry out preliminary validation measurements using targets for which positron scattering total cross sections might be considered to be well known.…”

“…In addition, here we also seek to investigate if there are any trends in the energy dependence of the positron total cross sections for all the cyclic ethers we have investigated, and if so can those trends be related to some of the more important physico-chemical properties (see Table I) of the species in question. [19][20][21][22][23] In Sec. II we give a summary of our experimental apparatus and measurement techniques.…”