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Kevin M. Lefrancois-Gagnon Robert C. Mawhinney 《Journal of computational chemistry》2020,41(29):2485-2503
The quantum theory of atoms in molecules (QTAIM) provides a theoretical foundation to determine the properties of functional groups through additive atomic contributions. Many studies have used QTAIM in their analyses with a variety of electronic structure methods, but it is unknown if the properties measured using one model chemistry, the combination of the electronic structure method and basis set, can be compared to those measured by another. Here, we evaluate the sensitivity of QTAIM functional group and bond critical point properties using six functionals and seven basis sets. High-level B2PLYPD3-BJ/aug-cc-pV5Z reference values are provided for 116 functional groups and the property sensitivity with respect to these values are evaluated based on absolute deviations and by assessing linear relationships. Functional group properties, including charges, dipoles, quadrupoles and volumes, were found to be mostly insensitive to choice of computational model chemistry. However, due to structural and topological inconsistencies, the 6-31G(d) basis set is not recommended for use. Bond critical point properties varied with choice of model chemistry, but models incorporating hybrid functionals and triple-ζ basis sets provided values suitable for use in regression studies. 相似文献
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To study the effect of the lateral substituents on the UV stability of high birefringence liquid crystals (LCs), computational chemistry was used to examine a series of high birefringence LCs based on a diphenyl-diacetylene (DPDA) central core, thiophene segments as elongated π-conjugated units and four electron-withdrawing groups (-F, -CF3, -OCF3, -CN) as lateral substituents. In the present study, geometry optimisations have been performed using the DFT/B3LYP/6-311G (d, p) method. Out of a series of functional and basis sets examined, the functional ωB97X-D and basis set 6-31G (d, p) are most successful in predicting charge transfer absorption. The theoretical study indicates that the enhancement of UV stability is related with the types, numbers and positions of the lateral substituents. The calculated results indicate that the electron-withdrawing groups can shorten triple bond length, decrease energy gap value and increase the absorption maxima of the high-Δn LCs, which is beneficial for good UV stability. With the introduction of increasing lateral electron-withdrawing substituent numbers, the DPDA derivatives would further improve UV stability. This work may provide an effective solution for the obstacle existed in the high-Δn LCs with DPDA structures and pave a way for their applications in LC photonics. 相似文献
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Substituent shifts of the energetics of four related ionization processes of pyridines and benzoic acids (Fig. 1) were investigated. The first process is core-electron ionization of gas-phase pyridines (Fig. 1A), while the second concerns gas-phase acid-base reaction between a substituted pyridine and a conjugated acid (Fig. 1B), and the third and fourth processes are the acid dissociation of substituted benzoic acids in aqueous solution (Fig. 1C) and in vacuum (Fig. 1D), respectively. Core-electron binding energies for the first process were calculated using density-functional theory with the scheme ΔEKS (PW86x-PW91c/TZP+Crel)//HF/6-31G*. Average absolute deviation of calculated core electron binding energy shifts at N atom in substituted pyridines from experiment was 0.08 eV. The shift at N coincides highly with that at a ring carbon atom. The four shifts corresponding to the four processes shown in Figs. 1A–D correlate strongly with one another, with numerical values fairly close to each other when expressed in unit of electron volts. 相似文献
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Victor Bassiloua Lahouari Ghaicha Mireille Privat René Bennes Emmanuel Tronel-Peyroz 《Journal of solution chemistry》1995,24(9):935-952
Activities of 2,5-dimethylpyridine in aqueous solution have been measured at eleven temperatures, two below and nine above the lower critical temperature of the mixture, by the dynamic method of Randall and Weber. Gibbs free energy, enthalpy and entropy are derived to obtain excess quantities and all the results are discussed in connection with the liquid-liquid phase separation, the critical situation and the association properties of the molecules. A comparison is also made with the aqueous 2,6-dimethylpyridine system. A new version of the phase diagram is proposed. 相似文献