using hartree–fock (hf) and ِِdensity functional theory (dft) calculations the thermodynamic properties such as thermal energy , , thermal enthalpy , , thermal entropy , , thermal gibbs free energy , , heat capacity ,cv, and molecular structures of several species involving in keto↔enol tautomerism related to acetaldehyde (a), 5,5-dimethyl-1,3-cyclohexanedione (dimedone) and  acetylacetone (aa) h...

In the present study, theoretical chemical reactivates Photo isomerization in Cis-Retinal as a Natural Photo switch in Vision. DFT hybrid functional, B3LYP and, post-HF method, were the theoretical methods applied utilizing G09 software. 6-31G+ (d,p) basis set employed for structural optimizations, and single point computations performed using B3LYP/6-31G+(d,p). The isomers cis molecule retinal...

In this article we provide a data package containing the topology files and parameters compatible with the CHARMM22 force field for thirteen non-natural amino acids. The force field parameters were derived based on quantum mechanical (QM) calculations involving geometry optimization and potential energy surface scanning at the HF 6-31G(d) and HF 6-311G(d,p) levels of theory. The resulting energ...

The proton transfer mechanism in malonaldehyde has been investigated from the points of view of the topological analysis of the electron localization function and of the catastrophe theory. The calculations were carried out at the B3LYP hybrid functional level with the ccp-VTZ basis set. Complementary calculations were performed at the HF, MP2, BLYP, and B3LYP levels with the STO-3G, 6-31G, and...

Ab initio HF/6-31G* Methode was employed to calculate  the bond length in 2- phosphinanes  when electronegative groups was at C-2 tend axial and equatorial positions. The magnitude of  the anomeric effect depends on the nature of the substituent, the effect of the substituent can be seen by comparing the bond length in 2-chloro and 2-boromo substituented phosphinanes. The effect of anomeric eff...

13C NMR spectra of molecules containing one or two benzene rings linked with CH=CH2, CH=CH (transor cis-), C C and CH=N groups revealed the existence of long range deuterium isotope effects on 13C chemical shifts. It was found that deuterium isotope effects over six bonds (6D) are related to the conformation of investigated molecules. Molecular torsional angles were calculated by ab initio HF/6...

a computational study of the electronic structure and stability of complexes formed between zeolite y and boric acid was carried out at the hf and b3lyp levels using 6-31g* basis set. five structures located as local minimum in pes of complex (structures d, e, f, g, and h). the most stable structure is formed due to hydrogen bonding between two hydroxyl of boric acid and both oxygen of ...

in this paper geometry optimization of two ionic complexes such as cr042-gly+1, and mo042- gly+i have been carried out at the hf and b3lyp levels oftheory with 6-31g* basis set in the gas phase. moreover, chemical shift andnatural bond of orbital (nbo) of these compounds have been obtainedusing nmr and nbo methods. finally, the obtained theoretical results werecompared with each other.