The Molecular Structures and Conformational Preferences of Bis(dimethylstibyl)-Sulfane and -Tellurane, E(SbMe2)2, E = S or Te, Me = CH3, by Density Functional Theory Calculations and Gas Electron Diffraction

1998 ◽  
Vol 53 (3) ◽  
pp. 381-385 ◽  
Author(s):  
Arne Haaland ◽  
Dimitry J. Shorokhov ◽  
Hans Vidar Volden ◽  
Hans Joachim Breunig ◽  
Michael Denker ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electron Diffraction ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Equilibrium Structure ◽  
Molecular Structures ◽  
Electron Diffraction Data ◽  
Functional Theory ◽  
Anti Conformer ◽  
Equilibrium Structures

Density functional theory calculations on E(SbMe2)2, E = S or Te, Me = CH3, indicate that the equilibrium structures are syn-syn or near syn-syn conformers with overall C2v or C2 symmetry. The calculations further indicate the existence of syn-anti conformers about 4 kJ mol-1 (E = S) or 1 kJ m ol-1 (E = Te) above the equilibrium structure. G as electron diffraction data show that both conform ers are present in gaseous S(SbMe2)2, while the presence of the syn-anti conformer in gaseous Te(SbMe2)2 is uncertain. The Sb - S and Sb - Te bond distances are 241.4(4) and 278.1(3) pm, respectively, the valence angles of the synsyn conformers are <SbSSb = 9 8.7(5)° and <SbTeSb = 91(2)°.

The Molecular Structures and Conformational Preferences of Bis(dimethylstibyl)- Oxane, -Sulfane and -Selane, E(SbMe2)2, E = O, S or Se, Me = CH3, by Density Functional Theory Calculations and Gas Electron Diffraction

1997 ◽  
Vol 52 (2) ◽  
pp. 296-300 ◽  
Author(s):  
Arne Haaland ◽  
Vasili Ivanovitch Sokolov ◽  
Hans Vidar Volden ◽  
Hans Joachim Breunig ◽  
Michael Denker ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Electron Diffraction ◽  
Density Functional ◽  
Lone Pair ◽  
Density Functional Theory Calculations ◽  
Molecular Structures ◽  
Gas Electron Diffraction ◽  
Electron Diffraction Data ◽  
Functional Theory ◽  
Anti Conformer

Abstract Density Functional Theory calculations on E(SbMe2)2, E = O, S or Se, Me = CH3, indicate that the equilibrium structures are syn-syn or near syn-syn conformers with over-all C2 symmetry. The barriers restricting rotation about E-Sb bonds are very low, the equilibrium values for the dihedral angles ϕ(Sb-E-Sb-lp) where lp denotes the direction of the electron lone pair on one of the Sb atoms are probably less than 45°. The calculations further indicate the existence of syn-anti conformers some 4 kJ mol-1 above the more stable syn-syn. Gas electron diffraction data show that both conformers are present in gaseous O(SbMe2)2, while the presence of the syn-anti conformer in gaseous Se(SbMe2)2 is uncertain; least-squares refinements yielded the mole fraction χ = 0.27(18). The Sb-O and Sb-Se bond distances are 197.6(14) and 255.1(5) pm respectively, the valence angles of the syn-syn conformers are <SbOSb = 122.3(16)° and <SbSeSb = 96.3(11)°. It is suggested that the wide <SbOSb angle is due to across-angle repulsion between the Sb atoms.

scholarly journals Including dispersion interactions in the ONETEP program for linear-scaling density functional theory calculations

2008 ◽  
Vol 465 (2103) ◽  
pp. 669-683 ◽  
Author(s):  
Quintin Hill ◽  
Chris-Kriton Skylaris
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Computational Cost ◽  
Density Functional Theory Calculations ◽  
Binding Energies ◽  
Molecular Structures ◽  
Dispersion Interactions ◽  
Biomolecular Systems ◽  
Functional Theory ◽  
High Level

While density functional theory (DFT) allows accurate quantum mechanical simulations from first principles in molecules and solids, commonly used exchange-correlation density functionals provide a very incomplete description of dispersion interactions. One way to include such interactions is to augment the DFT energy expression by damped London energy expressions. Several variants of this have been developed for this task, which we discuss and compare in this paper. We have implemented these schemes in the ONETEP program, which is capable of DFT calculations with computational cost that increases linearly with the number of atoms. We have optimized all the parameters involved in our implementation of the dispersion correction, with the aim of simulating biomolecular systems. Our tests show that in cases where dispersion interactions are important this approach produces binding energies and molecular structures of a quality comparable with high-level wavefunction-based approaches.

scholarly journals Molecular Structure and Vibrational Spectra of 2-Ethylhexyl Acrylate by Density Functional Theory Calculations

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Ottman Belaidi ◽  
Tewfik Bouchaour ◽  
Ulrich Maschke
Keyword(s):  
Density Functional Theory ◽  
Infrared Spectrum ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Molecular Geometry ◽  
Electron Diffraction Data ◽  
Functional Theory ◽  
Infrared Intensities ◽  
The Fourier Transform ◽  
Optimized Geometries

The Fourier transform infrared spectra (FTIR) of 2-ethylhexyl acrylate have been measured in liquid phase. The molecular geometry, vibrational frequencies, and infrared intensities have been calculated by using density functional theory. We found two local minima representing s-cis and s-trans conformations for 2-ethylhexyl acrylate molecule. The optimized geometries at DFT//B3LYP/6-311+ are in good agreement with electron diffraction data of methyl acrylate for the acrylic group. The two conformers were used for the interpretation of the experimental infrared spectrum of title compound. PED calculations are represented for a more complete and concise assignment. There is one band in the infrared spectrum at 1646 cm−1 that definitely indicates the conformer with s-trans arrangement of acrylic moiety to be present or not in the liquid 2-ethylhexyl acrylate.

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