Linear response and variational treatment are formulated for Hartree-Fock (HF) and Kohn-Sham density functional theory (DFT) methods and combined discrete-continuum solvation models that incorporate self-consistently induced dipoles and charges. Due to the variational treatment, analytic nuclear gradients can be evaluated efficiently for these discrete and continuum solvation models. The forces...

Compound (N,N-bis (salicylidene) 1,2-diaminophenylene) was prepared by condensation of ethanolsolution of 2-Hydroxybanzaldehyde and 1,2-diaminophenylene. The compound was characterized by1H NMR, infrared spectroscopy (FT-IR) data and analytical data. The geometrical parameters andenergies have been obtained from Density Functional Theory (DFT) B3LYP method and Hartree-Fock (HF) method with 3-21...

The relative stability of the different tautomers of hydantoin has been studied through the use of DFT method. The structures and the vibrational frequencies of all stable tautomers and all the transitions states connecting between them have been calculated at the B3LYP/6-311+G(d,p) level of theory in the gas phase and selected solvents using IE-PCM model. Final energies have been obtained in s...

A combined computational and (13)C NMR study was used to investigate the formation of mixed aggregates of 1-methoxyallenyllithium and lithium chloride in tetrahydrofuran (THF) solution. The observed and calculated chemical shifts, as well as the calculated free energies of mixed aggregate formation (MP2/6-31+G(d)), are consistent with the formation of a mixed dimer as the major species in solut...

Density-functional-based and ab initio calculations were implemented at different computational levels to estimate the binding energy of Zn2+ ion adsorbed on the available sites of a silicate MEL-type adsorbent. B3LYP and MP2 were used in combination with the 6-31G*, 6-31+G*, LanL2DZ, 6-311+G*, and Def2-TZVP basis sets. The zinc cation was found to preferentially occupy the 6MR sites followed b...

to investigation non-bonded interaction of the [cuf4]2- complex inside nanoring, we focus on the single wall boron-nitride b18n18 nanoring. thus, the geometry of b18n18 nanoring has been optimized by b3lyp method with epr-ii basis set and geometry of the [cuf4]2- complex has been optimized at b3lyp method with def2-tzvp basis set and stuttgart rsc 1997 effective core potential. also electronic ...

in this paper, electronic, structural, and spectroscopic properties of mono-, di-, tri-, andtetrafluorothiophenes and their radical cations are studied using the density functional theory andb3lyp method with 6-311++g** basis set. also the effects of the number and position of thesubstituent on the electrochemical properties of the thiophene ring have been studied usingoptimized structures obta...

A DFT-SOFM-RBFNN method is proposed to improve the accuracy of DFT calculations on Y-NO (Y = C, N, O, S) homolysis bond dissociation energies (BDE) by combining density functional theory (DFT) and artificial intelligence/machine learning methods, which consist of self-organizing feature mapping neural networks (SOFMNN) and radial basis function neural networks (RBFNN). A descriptor refinement s...

The quantitative influence of the choice of energy evaluation method used in the geometry optimization step prior to the calculation of molecular descriptors in QSAR and QSPR models was investigated. A total of 11 energy evaluation methods on three molecular datasets (toxicological compounds, aromatic compounds and PPARgamma agonists) were studied. The methods employed were: MMFF94 s, MM3* with...

Recently, a novel, neural-networks-based method, the DFT-NEURON method, was developed to improve the accuracy of first-principles calculations and was applied to correct the systematic deviations of the calculated heats of formation for small-to-medium-sized organic molecules (Hu, L. H.; Wang, X. J.; Wong, L. H.; Chen, G. H. J. Chem. Phys. 2003, 119, 11501). In this work, we examine its theoret...