Vibrational amplitudes for thionyl tetrafluoride and sulphur tetrafluoride

1965 ◽  
Vol 18 (10) ◽  
pp. 1575 ◽  
Author(s):  
MGK Pillai ◽  
K Ramaswamy ◽  
R Pichai
Keyword(s):  
Electron Diffraction ◽  
Oxygen Atom ◽  
Force Constant ◽  
Spectroscopic Data ◽  
Lone Pair ◽  
Electron Diffraction Data ◽  
Mean Square ◽  
Root Mean Square Amplitude ◽  
Energy Constants ◽  
Good Agreement

The potential energy constants and vibrational mean amplitudes for thionyl tetrafluoride were calculated using the Urey-Bradley Force Field (UBFF) with a view to finding out the influence of the oxygen atom on the SF4 group. It was found that the axial S-F stretching force constant is smaller than the equatorial S-F stretching force constant, which is consistent with the variation in the bond length. The behaviour of the oxygen atom is found to be similar to the lone pair of electrons in sulphur tetrafluoride. The vibrational mean amplitudes calculated from spectroscopic data are in very good agreement with the electron diffraction data. The large root mean square amplitude of vibration for equatorial-equatorial non-bonded fluorine atoms (0.099 Ǻ) in sulphur tetrafluoride indicates the possibility of incomplete inversion as pointed out by Chantry and Ewing.

scholarly journals Notizen:The G eneralised Mean Square Amplitudes of Vibration for Substituted Ethylenes Vinylidene Halides and their Deuterates

1971 ◽  
Vol 26 (4) ◽  
pp. 778-780
Author(s):  
S. Jeyapandian
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Spectroscopic Data ◽  
Electron Diffraction Data ◽  
Mean Square ◽  
Type C ◽  
The Mean

Abstract For six vinylidene halides the generalised mean square amplitudes of displacements parallel and perpendicular to the bond for both bonded and non-bonded atom distances are cal­culated from spectroscopic data using the method of Morino and Hirato. The results are discussed and the mean amplitu­des of these molecules (H2C=CX2) are compared with those from electron diffraction data for the similar molecules of the type C2X4.

Structural Phase Transition in Tetrafluoroaluminates

1982 ◽  
Vol 21 ◽  
Author(s):  
J.M. Launay ◽  
J.Y. Laval ◽  
A. Gibaud ◽  
A. Bulou ◽  
J. Nouet
Keyword(s):  
Electron Diffraction ◽  
Room Temperature ◽  
Structural Phase ◽  
The Other ◽  
Electron Diffraction Data ◽  
Temperature Phase ◽  
X Ray ◽  
Quadratic Phase ◽  
Low Temperature Phase ◽  
Good Agreement

ABSTRACTIt is shown that the detailed investigation of an irreversible SPT implies the combination of X-ray, neutron and electron diffraction data. This diffraction analysis is applied to K Al F4 and Rb Al F4. There is a good agreement between the three diffraction techniques in the case of Rb Al F4 where the SPT is reversible. On the other hand, for K Al F4 room temperature quadratic phase, electron diffraction exhibits exta spots which are not evidenced by X-ray and neutron diffraction. Finally the assumption of an orthorombic lattice from neutron scattering for the low temperature phase is consistant with electron diffraction results.

An Augmented, Small-Parameter Equation for the Squeeze-Film Journal Bearing

1970 ◽  
Vol 92 (3) ◽  
pp. 442-449 ◽  
Author(s):  
C. L. Strodtman
Keyword(s):  
Small Parameter ◽  
Shape Factor ◽  
Radial Displacement ◽  
Journal Bearing ◽  
Numerical Procedure ◽  
Squeeze Film ◽  
Mean Square ◽  
Root Mean Square Amplitude ◽  
Parameter Equation ◽  
Good Agreement

The asymptotic gas film equation for the squeeze-film journal bearing is solved for the quadratic and cubic terms in the series expansion in terms of the radial displacement. The load support calculated from this augmented, small parameter equation is compared to calculations from an all numerical procedure. Good agreement is shown to exist for large values of the radial displacement. A method of treating nonuniform excursion of the driving member by a root-mean-square amplitude and a shape factor is also given.

The Molecular Structures and Conformational Preferences of Simple Molecules Containing Bonds Between a Trivalent Group 15 and a Divalent Group 16 Element: The Molecular Structures of Dimethyl(methylthio)stibane and Dimethyl(methylseleno)stibane, (CH3)2SbECH3 E = S or Se, by Gas Electron Diffraction

1993 ◽  
Vol 48 (8) ◽  
pp. 1065-1068 ◽  
Author(s):  
Arne Haaland ◽  
Hans Peter Verne ◽  
Hans Vidar Volden ◽  
Hans Joachim Breunig ◽  
Sabahittin Gülec
Keyword(s):  
Electron Diffraction ◽  
Dihedral Angle ◽  
Diffraction Data ◽  
Lone Pair ◽  
Molecular Structures ◽  
Gas Electron Diffraction ◽  
Electron Diffraction Data ◽  
Conformational Preferences ◽  
Group 15 ◽  
Simple Molecules

Gas electron diffraction data of (CH3)2SbECH3 E = S or Se, show that the predominant conformer is one where the dihedral angle defined by the E–C bond, the Sb–E bond and the presumed direction of the lone pair at the Sb atom falls in the range –45 to +45°. The Sb–S and Sb–Se bond distances are 241.4(8) and 255.5(3) pm, respectively.

Molecular Constants of PClF4

1969 ◽  
Vol 24 (10) ◽  
pp. 1256-1258
Author(s):  
K. Venkateswarlu ◽  
C. P. Girijavallabhan
Keyword(s):  
Potential Energy ◽  
Spectroscopic Data ◽  
Mean Square ◽  
Coriolis Coupling ◽  
Coupling Coefficients ◽  
Molecular Constants ◽  
Shrinkage Effect ◽  
Energy Constants

Potential energy constants of the G.V.F.F. type, generalised mean square amplitudes of vibration, shrinkage effect and Coriolis coupling coefficients of PClF4 molecule are evaluated from spectroscopic data. The results are discussed in relation to the structure of the molecule.

Molecular force field for thionyl fluoride and sulphuryl fluoride

1967 ◽  
Vol 20 (6) ◽  
pp. 1055 ◽  
Author(s):  
R Pichai ◽  
MGK Pillai ◽  
K Ramaswamy
Keyword(s):  
Oxygen Atom ◽  
Potential Energy ◽  
Force Field ◽  
Spectral Data ◽  
Lone Pair ◽  
Molecular Force ◽  
Molecular Force Field ◽  
Energy Constants

The potential energy constants of thionyl fluoride and sulphuryl fluoride were calculated using a modified UBRF. The behaviour of the oxygen atom is found to be similar to that of the lone pair of electrons in thionyl fluoride. The vibrational mean amplitudes of thionyl fluoride and sulphuryl fluoride were also calculated from the vibrational spectral data.

Spin–spin interactions in polyphenyls

1967 ◽  
Vol 45 (14) ◽  
pp. 1707-1710 ◽  
Author(s):  
C. L. Gardner
Keyword(s):  
Electron Diffraction ◽  
Electron Diffraction Data ◽  
Zero Field ◽  
Triplet States ◽  
Zero Field Splitting ◽  
Structure Information ◽  
Weakly Coupled ◽  
Spin Interactions ◽  
Semi Empirical ◽  
Good Agreement

An attempt has been made, with some success, to interpret the zero field splitting parameters for the triplet states of molecules such as the polyphenyls where the subunits are weakly coupled and the molecules are probably nonplanar. The method used was a semi-empirical exciton theory, applied in particular to biphenyl and 1,3,5-triphenylbenzene. In these two cases it is found that structure information, in particular the angle between rings, obtained by this method is in good agreement with electron diffraction data.

scholarly journals Spectroscopic Analysis with Calculated Mean Amplitudes for P4O6 and P4O10

1971 ◽  
Vol 26 (5) ◽  
pp. 901-906
Author(s):  
S. J. Cyvin ◽  
B. N. Cyvin
Keyword(s):  
Electron Diffraction ◽  
Diffraction Data ◽  
Spectroscopic Analysis ◽  
Atomic Vibration ◽  
Electron Diffraction Data ◽  
Mean Square ◽  
Harmonic Force ◽  
Normal Coordinate ◽  
Mean Amplitudes Of Vibration ◽  
Symmetry Coordinates

Abstract Normal coordinate analyses are reported for P4O6 and P4O10 . Harmonic force constants are given in terms of precisely defined symmetry coordinates. The force fields are used to calculate mean amplitudes of vibration, which are compared with electron diffraction data, and some discrepancies are discussed. Calculated atomic vibration mean-square amplitudes, which are of interest in crystallographic studies, are also given.

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.

Crystal Structure Determination of Glycerol-Containing Lipids from Electron Diffraction Data. Use of Analog Compounds Based upon Configurational Isomers of Cyclopentane-1, 2, 3-TRIOL

1977 ◽  
Vol 35 ◽  
pp. 24-25
Author(s):  
Douglas L. Dorset ◽  
Anthony J. Hancock
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Diffraction Data ◽  
Structure Determination ◽  
Crystal Surface ◽  
Coherent Scattering ◽  
Crystal Structure Determination ◽  
Electron Diffraction Data ◽  
Polar Group ◽  
Axis Orientation

Lipids containing long polymethylene chains were among the first compounds subjected to electron diffraction structure analysis. It was only recently realized, however, that various distortions of thin lipid microcrystal plates, e.g. bends, polar group and methyl end plane disorders, etc. (1-3), restrict coherent scattering to the methylene subcell alone, particularly if undistorted molecular layers have well-defined end planes. Thus, ab initio crystal structure determination on a given single uncharacterized natural lipid using electron diffraction data can only hope to identify the subcell packing and the chain axis orientation with respect to the crystal surface. In lipids based on glycerol, for example, conformations of long chains and polar groups about the C-C bonds of this moiety still would remain unknown.One possible means of surmounting this difficulty is to investigate structural analogs of the material of interest in conjunction with the natural compound itself. Suitable analogs to the glycerol lipids are compounds based on the three configurational isomers of cyclopentane-1,2,3-triol shown in Fig. 1, in which three rotameric forms of the natural glycerol derivatives are fixed by the ring structure (4-7).

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