scholarly journals The Nature of the Hydrogen-Bond. I. The Delocalization Energy in the Hydrogen-Bond as Calculated by the Atomic-orbital Method

1954 ◽  
Vol 27 (7) ◽  
pp. 445-450 ◽  
Author(s):  
Hiroshi Tsubomura
Keyword(s):  
Hydrogen Bond ◽  
Atomic Orbital ◽  
Orbital Method ◽  
Delocalization Energy

From Atomic Orbitals to Molecular Orbitals and Chemical Bonds

2020 ◽  
pp. 150-187
Author(s):  
Jochen Autschbach
Keyword(s):  
Hydrogen Molecule ◽  
Atomic Orbital ◽  
Plane Waves ◽  
Basis Set ◽  
Orbital Method ◽  
Chemical Bonds ◽  
Atomic Orbitals ◽  
Hartree Fock ◽  
Generalized Matrix

It is shown how an aufbau principle for atoms arises from the Hartree-Fock (HF) treatment with increasing numbers of electrons. The Slater screening rules are introduced. The HF equations for general molecules are not separable in the spatial variables. This requires another approximation, such as the linear combination of atomic orbitals (LCAO) molecular orbital method. The orbitals of molecules are represented in a basis set of known functions, for example atomic orbital (AO)-like functions or plane waves. The HF equation then becomes a generalized matrix pseudo-eigenvalue problem. Solutions are obtained for the hydrogen molecule ion and H2 with a minimal AO basis. The Slater rule for 1s shells is rationalized via the optimal exponent in a minimal 1s basis. The nature of the chemical bond, and specifically the role of the kinetic energy in covalent bonding, are discussed in details with the example of the hydrogen molecule ion.

Use of Replaced Chalcones to Generate a 13C Chemical Shift Staging Factor for Chalcone and Its Derivate

2020 ◽  
Vol 12 (4) ◽  
pp. 464-472
Author(s):  
Thaís F. Giacomello ◽  
Gunar V. da S. Mota ◽  
Antônio M. de J. C. Neto ◽  
Fabio L. P. Costa
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Chemical Shift ◽  
Density Functional ◽  
Chemical Shifts ◽  
Atomic Orbital ◽  
Scaling Factor ◽  
Orbital Method ◽  
Beneficial Effects ◽  
Nuclear Magnetic

Chalcones have attracted the attention of researchers for decades, they are biologically classified as secondary metabolites of low molecular weight. These are considered as the precursors of flavonoids and they are widely distributed in plants such as vegetables, fruits, teas and spices. It has been demonstrating that chalcones possess many important bioactivities including properties of antioxidants and other evidence of its potential beneficial effects on health. Chalcone compounds and its derivatives have been showing a growing interest in the therapeutic properties. Nuclear magnetic resonance (NMR) spectroscopy is one of the most important tools for determining the structures of organic molecules. In the work present a 13C Nuclear magnetic resonance chemical shift protocol of chalcones and derivative based on the application of scaling factor with chalcone molecules. This protocol consists of using density functional theory with gauge-including atomic orbital method to calculating 13C chemical shifts and the application of a parameterized scaling factor in order to ensure accurate structural determination of chalcones and derivative.

FUSION RATE IN μtt IN MUONIC MOLECULAR ION USING LINEAR COMBINATION OF ATOMIC ORBITAL METHOD

2011 ◽  
Vol 20 (03) ◽  
pp. 629-636
Author(s):  
M. MAHDAVI ◽  
B. KALEJI ◽  
T. KOOHROKHI
Keyword(s):  
Reaction Rate ◽  
Transition Probability ◽  
Atomic Orbital ◽  
Fusion Reaction ◽  
Fusion Cross Section ◽  
Nuclear Interaction ◽  
Fusion Rate ◽  
Nuclear Potential ◽  
Orbital Method ◽  
Molecular Ion

In this paper, the tritium–tritium fusion reaction rate in a muonic molecular ion (μtt) is calculated by using a square-well nuclear potential as a complex for nuclear interaction between two tritones. The complex potential parameters are obtained by fitting process on fusion cross-section experimental data. The real and imaginary parts of the nuclear potential are calculated as Ur = -62531.87 (keV) and Ui = -165.63 (keV), respectively. A free parameter that is related to the radius of this potential is A = 0.004155. Also, considering the optical nuclear potential, the energy value of μtt muonic molecular ion is calculated. The fusion rate is calculated by liner combination of atomic orbital (LCAO) method. Finally, the reaction rate, λ, is obtained 0.28×1010 s -1 by calculating the transition probability through the potential barrier and the oscillation frequency of wave function.

A theoretical study of the 77Se NMR and vibrational spectroscopic properties of SenS8–n ring molecules

2002 ◽  
Vol 80 (11) ◽  
pp. 1435-1443 ◽  
Author(s):  
J Komulainen ◽  
R S Laitinen ◽  
R J Suontamo
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Chemical Shifts ◽  
Atomic Orbital ◽  
Geometry Optimization ◽  
Spectroscopic Properties ◽  
Basis Sets ◽  
Orbital Method ◽  
Hybrid Functional ◽  
Ring Molecules

The structures and spectroscopic properties of SenS8–n ring molecules have been studied by the use of ab initio molecular orbital techniques and density functional techniques involving Stuttgart relativistic large core effective core potential approximation with double zeta basis sets for valence orbitals augmented by two polarization functions for both sulfur and selenium. Full geometry optimizations have been carried out for all 30 isomers at the Hartree-Fock level of theory. The optimized geometries and the calculated fundamental vibrations and Raman intensities of the SenS8–n molecules agree closely with experimental information where available. The nuclear magnetic shielding tensor calculations have been carried out by the Gauge-independent atomic orbital method at the DFT level using Becke's three-parameter hybrid functional with Perdew/Wang 91 correlation. The isotropic shielding tensors correlate well with the observed chemical shift data. The calculated chemical shifts provide a definite assignment of the observed 77Se NMR spectroscopic data and can be used in the prediction of the chemical shifts of unknown SenS8–n ring molecules.Key words: selenium sulfides, ab initio, DFT, effective core potentials, geometry optimization, energetics, fundamental vibrations, 77Se chemical shifts.

scholarly journals Spectroscopic (FTIR, UV-Vis and NMR), theoretical investigation and molecular docking of substituted 1,8-dioxodecahydroacridine derivatives

2020 ◽  
Vol 85 (1) ◽  
pp. 53-66
Author(s):  
Krishna Yadav ◽  
Abhishek Kumar ◽  
Sanchari Begam ◽  
Khondekar Nurjamal ◽  
Amarendra Kumar ◽  
...  
Keyword(s):  
Succinic Acid ◽  
Atomic Orbital ◽  
Dft Method ◽  
Docking Studies ◽  
Potential Energy Distribution ◽  
Orbital Method ◽  
Reactivity Descriptors ◽  
Biologically Relevant ◽  
Antileishmanial Drug ◽  
Ft Ir

Recently, substituted 1,8-dioxodecahydroacridine derivatives have been investigated and found to possess a wide variety of biological and pharmacological activities. Two of these biologically relevant N-heterocyclic scaffolds, 2-(9-(4-methoxyphenyl)-3,3,6,6-tetramethyl-1,8-dioxo-1,2,3,4,5,6,7,8- -octahydroacridin-10(9H)-yl)succinic acid (MTDOSA) and 2-(3,3,6,6-tetramethyl- 9-(4-nitrophenyl)-1,8-dioxo-1,2,3,4,5,6,7,8-octahydroacridin-10(9H)-yl)- succinic acid (NTDOSA), have been studied in ground and first excited state using DFT method employing B3LYP/6-311++G(d,p) level of theory. Quantum chemical calculations of geometrical structure and vibrational wavenumbers of MTDOSA and NTDOSA were carried out using DFT method. The experimental FT-IR spectra of the compounds were recorded in the range 4000?400 cm-1 and comprehensively interpreted on the basis of potential energy distribution. The global reactivity descriptors are calculated and discussed. Moreover, 1H- and 13C-NMR spectral data have been calculated using the gauge independent atomic orbital method and compared with experimental spectra. The docking studies reveal that the compounds MTDOSA and NTDOSA have strong binding affinity toward the target protein 5KLH. Thus, the compounds have a possible use as an antileishmanial drug.

scholarly journals Spin-resolved atomic orbital model refinement for combined charge and spin density analysis: application to the YTiO3 perovskite

2021 ◽  
Vol 77 (2) ◽  
pp. 96-104
Author(s):  
Iurii Kibalin ◽  
Ariste Bolivard Voufack ◽  
Mohamed Souhassou ◽  
Béatrice Gillon ◽  
Jean-Michel Gillet ◽  
...  
Keyword(s):  
Neutron Diffraction ◽  
Atomic Orbital ◽  
Orbital Method ◽  
Orbital Ordering ◽  
X Ray Diffraction ◽  
X Ray ◽  
Analysis Application ◽  
Density Analysis ◽  
Perovskite Crystal ◽  
Polarized Neutron

A new crystallographic method is proposed in order to refine a spin-resolved atomic orbital model against X-ray and polarized neutron diffraction data. This atomic orbital model is applied to the YTiO3 perovskite crystal, where orbital ordering has previously been observed by several techniques: X-ray diffraction, polarized neutron diffraction and nuclear magnetic resonance. This method gives the radial extension, orientation and population of outer atomic orbitals for each atom. The interaction term between Ti3+, Y3+ cations and O2− ligands has been estimated. The refinement statistics obtained by means of the orbital method are compared with those obtained by the multipole model previously published.

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