A linear regression correction approach has been developed successfully to account for the electron correlation energy missing in Hartree–Fock calculation and to reduce the calculation errors of density functional theory. The numbers of lone-pair electrons, bonding electrons and inner layer electrons in molecules, and the number of unpaired electrons in the composing atoms in their ground state...

A linear regression correction approach has been developed successfully to account for the electron correlation energy missing in Hartree-Fock calculation and to reduce the calculation errors of density functional theory. The numbers of lone-pair electrons, bonding electrons and inner layer electrons in molecules, and the number of unpaired electrons in the composing atoms in their ground state...

The geometrical structures and properties of conjugated polyhelicenes and annelated fused-ring carbon helices with analogous frameworks were theoretically studied at the HF/6-31G and B3LYP/6-31G levels. These studies focused on the stability of the fused-ring structures with special emphasis on the helical geometrical arrangements. To elucidate bonding patterns, the orbitals, electron density c...

Self-assembled monolayers (SAMs) of omega-substituted biphenylthiolates (omega-MBP) on gold were characterized by spectral ellipsometry, X-ray photoelectron spectroscopy (XPS), infrared reflection absorption spectroscopy (IRRAS), and vibrational sum frequency generation spectroscopy (VSFG). The vibrational studies of the SAMs were supported by an ab initio frequency analysis at HF/6-31G and BP8...

qspr study on benzene derivatives have been made using recently introduced topological methodology. in this study the relationship between the randic' (x'), balaban (j), szeged (sz),harary (h), wiener (w), hyperwiener and wiener polarity (wp) to the thermal energy (eth), heat capacity (cv) and entropy (s) of benzene derivatives is represented.physicochemical properties are taken from the quantu...

We investigated spectroscopic and dynamic fluorescence properties of the S1 <-- S0 transitions of three intramolecularly hydrogen-bonded molecules, 1,8-dihydroxyanthraquinone (1,8-DHAQ), 1-aminoanthraquinone (1-AAQ), and 9-hydroxyphenalenone (9-HPA), by determining their fluorescence excitation spectra and state-selective fluorescence lifetimes under supersonic jet conditions. Moreover, ab init...

HF level of ab initio calculations with basis-set 6-31G including full counterpoise correction hasbeen applied to compute the AspHis potential with the Ser and HisSer potential with the Asp inAspHisSer trimer. The potential energy surface has a minimum of -16.765 kcal/mol in R1=1.912nm and R2=2.719 nm. The optimum computed curves for two interactions were fitted withintermolecular pair potentia...

the combination of quantum mechanics (qm) and molecular mechanics (mm) methods hasbecome alternative tool for many applications that pure qm and mm could not be suitable.the qm/mm method has been used for different type of problems, for example: structuralbiology, surface phenomena, and liquid phase. in this paper we have performed these methods forsome antibiotics and vitamins and then we comp...

The acid dissociation (ionization) constant pK(a) is one of the fundamental properties of organic molecules. We have evaluated different computational strategies and models to predict the pK(a) values of substituted phenols using partial atomic charges. Partial atomic charges for 124 phenol molecules were calculated using 83 approaches containing seven theory levels (MP2, HF, B3LYP, BLYP, BP86,...

The conformational flexibility of the expanded porphyrins allows them to achieve different topologies with distinct aromaticities and nonlinear optical properties (NLOP). For instance, it is possible to switch between Möbius and Hückel topologies applying only small changes in the external conditions or in the structure of the ring. In this work, we evaluate the electronic and vibrational contr...