Properties of atoms in molecules: structures and reactivities of boranes and carboranes

1992 ◽  
Vol 70 (2) ◽  
pp. 657-676 ◽  
Author(s):  
R. F. W. Bader ◽  
D. A. Legare
Keyword(s):  
Charge Density ◽  
Molecular Structures ◽  
Atoms In Molecules ◽  
Basis Set ◽  
Reduced Order ◽  
Atomic Interactions ◽  
Polarization Functions ◽  
Experimental Findings ◽  
Scf Calculations ◽  
Good Agreement

The energies, geometries, and charge distributions of the closo-, nido-, and arachno-boranes and closo-carboranes are determined in SCF calculations using a contracted (9s,5p) basis set of Huzinaga, supplemented with polarization functions. Good agreement is obtained between the experimental and calculated geometries. Molecular structures are assigned on the basis of the bond paths defined by the topology of the charge density using the theory of atoms in molecules. This theory is used to characterize the atomic interactions and to account for the stabilities of these electron-deficient systems. It is shown that their stability is a consequence of the delocalization of charge over the surfaces of the three- and four-membered rings of atoms that result from the formation of bonds of reduced order, a delocalization that is itself essential to the formation of the ring bonds. The Laplacian of the charge density is used to predict the sites of nucleophilic and electrophilic attack in these molecules, predictions that are in agreement with known experimental findings. Keywords: boranes, carboranes, charge density, Laplacian of ρ.

scholarly journals Synthesis, structural characterization and comparison of experimental and theoretical results by DFT level of molecular structures of 1,2,3-triazoles derived from 5-chloroisatin

2017 ◽  
Vol 5 (2) ◽  
pp. 91
Author(s):  
Zineb Tribak ◽  
Mohammed Skalli ◽  
Omar Senhaji ◽  
Youssef Kandri Rodi
Keyword(s):  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
Molecular Structures ◽  
Basis Set ◽  
Dipolar Cycloaddition ◽  
Nmr Characterization ◽  
The Stability ◽  
Experimental Findings ◽  
Good Agreement

This work deals about the synthesis, NMR characterization and the density functional method (B3LYP) with the 6-31G basis set of 1, 3-dipolar cycloaddition reactions between the two azides as dipoles and propargylchloroisatin as dipolarophile. Furthermore, DFT calculations were used to study the nucleophile–electrophile interactions of the azides and dipolarophile and also the stability between the regioisomers comparing their energy. Our calculations are in a good agreement with the experimental findings.

Tests of second-generation and third-generation density functionals for electron affinities of the alkylthio radicals

2014 ◽  
Vol 13 (04) ◽  
pp. 1450030 ◽  
Author(s):  
Aifang Gao ◽  
Aiguo Li
Keyword(s):  
Dft Method ◽  
Absolute Error ◽  
Molecular Structures ◽  
Basis Set ◽  
Density Functionals ◽  
Electron Affinities ◽  
Generalized Gradient ◽  
Experimental Values ◽  
P Type ◽  
Good Agreement

The molecular structures and electron affinities of the R – S / R – S -( R = CH 3, C 2 H 5, n- C 3 H 7, n- C 4 H 9, n- C 5 H 11, i- C 3 H 7, i- C 4 H 9, t- C 4 H 9) species have been studied using 17 pure and hybrid density functionals (five generalized gradient approximation (GGA) methods, six hybrid GGAs, one meta GGA method and five hybrid meta GGAs). The basis set used in this work is of double-ζ plus polarization quality with additional diffuse s- and p-type functions, denoted by DZP++. The geometries are fully optimized with each DFT method and discussed. Harmonic vibrational frequencies are found to be within 3.5% of available experimental values for most functionals. Three different types of the neutral-anion energy separations have been presented. The theoretical electron affinities of alkylthio radicals are in good agreement with the experiment data. The M06 method is very good for the adiabatic electron affinity calculations, and the average absolute error is 0.0439 eV. The HCTH method performs better for EA prediction. The M06-HF, mPWPW91, VSXC and B98 are also reasonable. The most reliable adiabatic electron affinities are predicted to be 1.864 eV ( CH 3 S ), 1.946 eV ( C 2 H 5 S ), 1.959 eV (n- C 3 H 7 S ), 1.970 eV (n- C 4 H 9 S ), 1.982 eV (n- C 5 H 11 S ), 2.053 eV (i- C 3 H 7 S ), 1.991 eV (i- C 4 H 9 S ) and 2.100 eV (t- C 4 H 9 S ) at the M06/DZP++ level of theory, respectively.

Ab Initio Calculations of the Molecular Structures and the Electronic Properties of Sulfur-containing Compounds: III. Thioacrolein (CH2=CH–CH=S) and Thioglyoxal (S = CH–CH=S)

1982 ◽  
Vol 37 (2) ◽  
pp. 125-128
Author(s):  
Tae-Kyu Ha ◽  
M. T. Nguyen ◽  
L. Vanquickenborne
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Electronic Properties ◽  
Gradient Method ◽  
Molecular Structures ◽  
Basis Set ◽  
Double Zeta ◽  
Scf Calculations ◽  
Sulfur Containing ◽  
Sulfur Containing Compounds

Abstract Results of ab initio SCF calculations on thioacrolein (CH2=CH-CH=S) and thioglyoxal (S=CH-CH=S) are reported. The geometries are optimized by the analytical gradient method using the double zeta (DZ) basis set. The trans conformers of these molecules are calculated to be more stable than the cis conformer by 2.06 and 4.31 kcal/mol, respectively.

Theoretical predictions of the molecular structure of sulphur tetrafluoride

1975 ◽  
Vol 28 (9) ◽  
pp. 2069 ◽  
Author(s):  
L Radom ◽  
III HF Schaefer
Keyword(s):  
Basis Set ◽  
Basis Sets ◽  
Structure Theory ◽  
Equilibrium Geometry ◽  
Double Zeta ◽  
Theoretical Predictions ◽  
Self Consistent Field ◽  
Polarization Functions ◽  
Hypervalent Molecules ◽  
Scf Calculations

The equilibrium geometry of the SF4 molecule has been investigated by means of ab initio electronic structure theory. Self-consistent-field (SCF) calculations employing a minimum basis set (MBS) incorrectly predict SF4 to have a square- pyramidal (C4V) structure. The correct qualitative prediction of a C2V geometry is obtained with a basis of nearly double zeta quality. Comparable calculations on H2S and SF2 suggest that it may only be for hypervalent molecules containing sulphur that minimum basis sets are inappropriate. However, polarization functions seem to be necessary for an accurate prediction of S-F bond distances.

An ab Initio SCF Study on the Stability and Structure of H2CN+ · nN2 Clusters

1983 ◽  
Vol 38 (8) ◽  
pp. 855-858 ◽  
Author(s):  
Tae-Kyu Ha ◽  
Minh Tho Nguyen
Keyword(s):  
Ab Initio ◽  
Basis Set ◽  
Localized Orbitals ◽  
Heats Of Formation ◽  
Charge Distributions ◽  
The Stability ◽  
Scf Calculations ◽  
Good Agreement

Abstract The clustering energies and geometries of the H2CN+ · nN2 (n = 1, 2 and 3) species have been determined by ab initio SCF calculations with the 4-31G basis set. The calculated clustering energies are in good agreement with the experimentally estimated heats of formation of the cor-responding clusters. The stability of various conformers has been studied in terms of localized orbitals and charge distributions.

Ab Initio Calculations of the Molecular Structures and the Electronic Properties of Phospha-AlkynesR-C≡P(R=H,CH3,NH2,OH, F and Cl)

1984 ◽  
Vol 39 (2) ◽  
pp. 169-174 ◽  
Author(s):  
Minh Tho Nguyen
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Electronic Properties ◽  
Molecular Structures ◽  
Basis Sets ◽  
Effect Of Substituents ◽  
Force Method ◽  
Double Zeta ◽  
Polarization Functions ◽  
Scf Calculations

Results of ab initio SCF calculations on phospha-alkynes R-C≡P with R=H. CH3, NH2, OH. F and Cl are reported. The geometries were optimized by the force method with analytical gradient employing double zeta (DZ) basis sets. Various molecular and one-electron properties are calculated with double zeta plus polarization functions (DZ + P) and compared with experimental ones. The effect of substituents is analysed in terms of computed properties.

Basis set dependence of SO stretching frequencies and its consequences for IR and VCD spectra predictions

2020 ◽  
Vol 22 (48) ◽  
pp. 27979-27986
Author(s):  
Kevin Scholten ◽  
Elric Engelage ◽  
Christian Merten
Keyword(s):  
Ir Spectra ◽  
Model Systems ◽  
Basis Set ◽  
Polarization Functions

Using chiral tosylates as model systems we evaluate the effect of diffuse and polarization functions on the quality of predicted VCD and IR spectra. Polarization functions on sulfur are shown to be important to reliable determine ACs using VCD.

Ground Flutter Simulation Test Based on Reduced Order Modeling of Aerodynamics by CFD/CSD Coupling Method

2019 ◽  
Vol 11 (01) ◽  
pp. 1950008
Author(s):  
Binwen Wang ◽  
Xueling Fan
Keyword(s):  
Aerodynamic Force ◽  
Test System ◽  
Simulation Test ◽  
Robust Controller ◽  
Test Technique ◽  
Reduced Order ◽  
Aerodynamic Model ◽  
Flutter Boundary ◽  
Computational Fluid Dynamics Cfd ◽  
Good Agreement

Flutter is an aeroelastic phenomenon that may cause severe damage to aircraft. Traditional flutter evaluation methods have many disadvantages (e.g., complex, costly and time-consuming) which could be overcome by ground flutter test technique. In this study, an unsteady aerodynamic model is obtained using computational fluid dynamics (CFD) code according to the procedure of frequency domain aerodynamic calculation. Then, the genetic algorithm (GA) method is adopted to optimize interpolation points for both excitation and response. Furthermore, the minimum-state method is utilized for rational fitting so as to establish an aerodynamic model in time domain. The aerodynamic force is simulated through exciters and the precision of simulation is guaranteed by multi-input and multi-output robust controller. Finally, ground flutter simulation test system is employed to acquire the flutter boundary through response under a range of air speeds. A good agreement is observed for both velocity and frequency of flutter between the test and modeling results.

Disorientations in dislocation structures: Formation and spatial correlation

2002 ◽  
Vol 17 (9) ◽  
pp. 2433-2441 ◽  
Author(s):  
Wolfgang Pantleon
Keyword(s):  
Plastic Deformation ◽  
Spatial Correlation ◽  
Distribution Functions ◽  
Scaling Behavior ◽  
Dislocation Dynamics ◽  
Slip Systems ◽  
Experimental Findings ◽  
Good Agreement

During plastic deformation, dislocation boundaries are formed and orientation differences across them arise. Two different causes lead to the formation of two kinds of deformation-induced boundaries: a statistical trapping of dislocations in incidental dislocation boundaries and a difference in the activation of slip systems on both sides of geometrically necessary boundaries. On the basis of these mechanisms, the occurrence of disorientations across both types of dislocation boundaries is modeled by dislocation dynamics. The resulting evolution of the disorientation angles with strain is in good agreement with experimental observations. The theoretically obtained distribution functions for the disorientation angles describe the experimental findings well and explain their scaling behavior. The model also predicts correlations between disorientations in neighboring boundaries, and evidence for their existence is presented.

scholarly journals DFT calculation and assignment of vibrational spectra of aryl and alkyl chlorophosphates

2014 ◽  
Vol 12 (2) ◽  
pp. 153-163
Author(s):  
Viktor Anishchenko ◽  
Vladimir Rybachenko ◽  
Konstantin Chotiy ◽  
Andrey Redko
Keyword(s):  
Vibrational Spectra ◽  
Basis Sets ◽  
Heavy Atoms ◽  
Wide Range ◽  
Complete Assignment ◽  
Key Factor ◽  
Polarization Functions ◽  
Experimental Values ◽  
Semi Empirical ◽  
Good Agreement

AbstractDFT calculations of vibrational spectra of chlorophosphates using wide range of basis sets and hybrid functionals were performed. Good agreement between calculated and experimental vibrational spectra was reached by the combination of non-empirical functional PBE0 with both middle and large basis sets. The frequencies of the stretching vibrations of the phosphate group calculated using semi-empirical functional B3LYP for all basis sets deviate significantly from the experimental values. The number of polarization functions on heavy atoms was shown to be a key factor for the calculation of vibrational frequencies of organophosphates. The importance of consideration of all the stable rotamers for a complete assignment of fundamental modes was shown.

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