N.M.R.-Studies of Bond Order in Azulene, Biphenylene and 1,6-Methano[10]annulene

1990 ◽  
Vol 43 (9) ◽  
pp. 1541 ◽  
Author(s):  
MJ Collins ◽  
S Sternhell ◽  
CW Tansey
Keyword(s):  
Experimental Data ◽  
Ground State ◽  
Bond Order ◽  
Membered Ring ◽  
Coupling Constants ◽  
Bond Orders ◽  
Bond Lengths ◽  
Theoretical Predictions ◽  
Electron Distributions ◽  
Good Agreement

The 4J(H-C-C-Me) coupling constants of methyl-substituted derivatives, probes of bond order, have been used to examine the ground-state π- electron distributions in azulene (1), biphenylene (2) and 1,6- methano [10] annulene (3). The experimental data obtained are in good agreement with theoretical predictions for biphenylene (2) and provide some evidence for π-electron disproportionation towards the five-membered ring in azulene (1). The bond orders in 1,6-methano [10] annulene (3) obtained in this work are at variance with those predicted on the grounds of bond lengths.

Ground states of conjugated molecules. XVII. The l.c.a.o. s.c.f. m.o. treatment of compounds containing nitrogen and oxygen

1970 ◽  
Vol 315 (1523) ◽  
pp. 457-464 ◽  
Keyword(s):  
Experimental Data ◽  
Ground State ◽  
Ground States ◽  
Resonance Integral ◽  
Conjugated Molecules ◽  
Bond Lengths ◽  
Conjugated Hydrocarbons ◽  
Good Account ◽  
The One ◽  
Good Agreement

In a recent paper (Dewar & Harget 1970) we described an l.c.a.o. s.c.f. m.o. treatment which gave an extremely good account of the ground-state properties of conjugated hydrocarbons. This treatment differed from the previous procedure used in this department, in that the one-electron core resonance integral B is evaluated using theMulliken approximation, B = KS . We now describe an extension of this treatment to conjugated molecules containing nitrogen or oxygen. Calculated heats of atomization and bond lengths are given for some nitrogen and oxygen compounds, and are in good agreement with experimental data.

LCAO MO CALCULATIONS ON A SERIES OF NITRILES AND SOME RELATED MOLECULES BY A METHOD OF SELF-CONSISTENT FORMAL CHARGES

1964 ◽  
Vol 42 (6) ◽  
pp. 1323-1332 ◽  
Author(s):  
J. B. Moffat
Keyword(s):  
Experimental Data ◽  
Input Data ◽  
Electron Systems ◽  
Bond Orders ◽  
Mo Calculations ◽  
Bond Lengths ◽  
Triple Bonds ◽  
Self Consistent ◽  
Good Agreement ◽  
Lcao Mo

A method of self-consistent charges has been applied to an LCAO MO calculation of a series of nitriles and some related molecules. The π-electron bond orders and π-electron densities were calculated for all the molecules considered. The entire calculation was programmed for operation on the IBM 1620 with alterations of the input data for the different molecules. The calculated bond orders yield bond lengths for C—C and C=C bonds in good agreement with experimental data, except when two or more triple bonds are present in the molecule. By the assumption of additivity of the bond orders obtained for the two orthogonal pi-electron systems, bond orders are obtained which yield bond lengths in satisfactory agreement with the experimental results for all CC bonds. For the nitrile bonds the calculated bond orders were fitted to a linear equation with the experimental bond lengths.

scholarly journals THE METHOD OF INCREMENTS — A WAVEFUNCTION-BASED AB-INITIO CORRELATION METHOD FOR SOLIDS

2007 ◽  
Vol 21 (13n14) ◽  
pp. 2204-2214 ◽  
Author(s):  
BEATE PAULUS
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Ground State ◽  
Infinite System ◽  
Correlation Energy ◽  
Correlation Method ◽  
Many Body ◽  
Hartree Fock ◽  
The Many ◽  
Good Agreement

The method of increments is a wavefunction-based ab initio correlation method for solids, which explicitly calculates the many-body wavefunction of the system. After a Hartree-Fock treatment of the infinite system the correlation energy of the solid is expanded in terms of localised orbitals or of a group of localised orbitals. The method of increments has been applied to a great variety of materials with a band gap, but in this paper the extension to metals is described. The application to solid mercury is presented, where we achieve very good agreement of the calculated ground-state properties with the experimental data.

On the π-Electron Content of Bonds and Rings in Benzenoid Hydrocarbons

2004 ◽  
Vol 59 (4-5) ◽  
pp. 295-298 ◽  
Author(s):  
Ivan Gutman ◽  
Tetsuo Morikawa ◽  
Susumu Narita
Keyword(s):  
Bond Order ◽  
Membered Ring ◽  
Electron Content ◽  
Bond Orders ◽  
Double Bonds ◽  
Benzenoid Hydrocarbons ◽  
Carbon Bond ◽  
Carbon Carbon Bond ◽  
Carbon Carbon Bonds ◽  
Single Bonds

The Pauling bond order can be viewed as a measure of the π-electron content of the respective carbon-carbon bond. In benzenoid hydrocarbons its values lie between 0 (in the case of essential single bonds) and 1 (in the case of essential double bonds). If the benzenoid molecule does not possess essential single and double bonds, then the Pauling bond orders are greater than 0 and less than 1, but may assume values arbitrarily close to 0 and 1. The π-electron content of a ring is equal to the sum of the π-electron contents of the carbon-carbon bonds forming this ring. We show that in benzenoid hydrocarbons the π-electron content of any (six-membered) ring lies between 0 and 5.5. If the molecule does not possess essential single and double bonds, then the π-electron content of any ring is greater than 0 and less than 5.5, but may assume values arbitrarily close to 0 and 5.5.

scholarly journals Study of sub-barrier fusion of 36S+50Ti,51V systems

2019 ◽  
Vol 223 ◽  
pp. 01013
Author(s):  
Giulia Colucci ◽  
Giovanna Montagnoli ◽  
Alberto M. Stefanini ◽  
Kouichi Hagino ◽  
Antonio Caciolli ◽  
...  
Keyword(s):  
Experimental Data ◽  
Comparative Study ◽  
Excitation Function ◽  
Ground State ◽  
Weak Coupling ◽  
Coupling Scheme ◽  
Excitation Functions ◽  
Coupled Channels ◽  
Barrier Distribution ◽  
Good Agreement

A detailed comparative study of the sub-barrier fusion of the two near-by systems 36S+50Ti,51V was performed at the National Laboratories of Legnaro (INFN). Aim of the experiment was the investigation of possible effects of the non-zero spin of the ground state of the 51V nucleus on the sub-barrier excitation function, and in particular on the shape of the barrier distribution. The results sh w that the two measured excitation functions are very similar down to the level of 20 - 30 μb. The same is observed for the two barrier distributions. Coupled-channels calculations have been performed and are in good agreement with the experimental data. This result indicates that the low-lying levels in 51V can be interpreted in the weak-coupling scheme, that is, 51V(I) = 50Ti(2+)⊗ p(1 f7/2).

scholarly journals New test of the dynamic theory of neutron diffraction by a moving grating

2018 ◽  
Vol 177 ◽  
pp. 03005
Author(s):  
Maxim Zakharov ◽  
Alexander Frank ◽  
German Kulin ◽  
Semyon Goryunov
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Neutron Diffraction ◽  
Dynamic Theory ◽  
Time Of Flight ◽  
Dynamical Theory ◽  
Zero Order ◽  
Significant Suppression ◽  
Theoretical Predictions ◽  
Good Agreement

Recently, multiwave dynamical theory of neutron diffraction by a moving grating was developed. The theory predicts that at a certain height of the grating profile a significant suppression of the zero-order diffraction may occur. The experiment to confirm predictions of this theory was performed. The resulting diffracted UCNs spectra were measured using time-of-flight Fourier diffractometer. The experimental data were compared with the results of numerical simulation and were found in a good agreement with theoretical predictions.

Bond order-bond length relationships in conjugated hydrocarbons - the microwave spectrum and structure of 3,4-dimethylenecyclobutene

1983 ◽  
Vol 36 (4) ◽  
pp. 639 ◽  
Author(s):  
RD Brown ◽  
PD Godfry ◽  
BT Hart ◽  
AL Ottrey ◽  
M Onda ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Ab Initio ◽  
Bond Length ◽  
Bond Order ◽  
Microwave Spectrum ◽  
Basis Set ◽  
Molecular Orbital Calculations ◽  
Bond Orders ◽  
Bond Lengths ◽  
Typical Error

The microwave spectrum of the benzene isomer 3,4-dimethylenecyclobutene including spectra of all possible single 13C-substituted and sufficient singly and doubly D-substituted species to give a complete r5 geometry, have been measured and analysed. An estimate of the re geometry has also been derived. The additional precise CC bond lengths obtained for an unsubstituted, conjugated hydrocarbon enable us to examine bond order-bond length relationships more thoroughly than has previously been possible. The CC bond lengths exhibit a noticeably better correlation with SCFMO bond orders than with simple H�ckel bond orders. Further confirmatory measurements of the dipole moment of dimethylenecyclobutene have been made. Ab initio molecular orbital calculations using a 6-31G basis set give an optimized geometry with CC bond lengths within 2 pm of the r5 values. The computed dipole moment agrees almost exactly with experiment but a corresponding calculation on fulvene is discrepant with experiment by 0.16 D, which is probably a more typical error.

Accurate heats of atomization and accurate bond lengths.: II. Polyenes and polyphenyls

1968 ◽  
Vol 46 (12) ◽  
pp. 2041-2051 ◽  
Author(s):  
Donald H. Lo ◽  
M. A. Whitehead
Keyword(s):  
Steric Hindrance ◽  
Bond Order ◽  
Minimum Energy ◽  
Stabilization Energy ◽  
Direct Measure ◽  
Bond Lengths ◽  
Molecular Stability ◽  
Linear Polyenes ◽  
Substituted Polyenes ◽  
Good Agreement

Accurate heats of atomization and bond lengths are calculated for several polyenes and polyphenyls, using the s.c.f.–l.c.a.o.–m.o. method described in Part I (1). Localization of π and σ bonds is found in the linear polyenes and in the diphenyl-substituted polyenes. The estimated stabilization energy per CC bond (SECC) gives a direct measure of the π electron conjugation and σ bond compression. Conjugation stabilization and steric hindrance are analyzed in 1,3-butadiene and biphenyl; the predicted geometries are in good agreement with experimental results. The minimum energy for any planar structure is found to be associated with the s.c.f. calculated bond lengths. The validity of pi bond order as a measure of molecular stability in the polyphenyls is discussed.

Thermal Behavior and Friction in Journal Bearings

1970 ◽  
Vol 92 (3) ◽  
pp. 373-380 ◽  
Author(s):  
Al. Nica
Keyword(s):  
Experimental Data ◽  
Thermal Behavior ◽  
Heat Dissipation ◽  
Journal Bearings ◽  
Friction Torque ◽  
Operating Characteristics ◽  
Lubricant Flow ◽  
Theoretical Predictions ◽  
Theoretical Results ◽  
Good Agreement

This paper deals with friction and the field of temperature in the lubricant film of journal bearings. Theoretical results regarding the thermal behavior are checked with experimental data and good agreement is found. Emphasis is put on the variation of temperature and lubricant flow with the operating characteristics of the bearing and it is seen that theoretical predictions for minima of friction torque are backed by temperature measurements. Further on, the friction torque and the mechanism of heat dissipation in bearings are dealt with, in order to verify the assumptions used in the calculation schemes. The means of efficiently cooling the bearing are also discussed, as well as the part played by the divergent zone in this process.

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