scholarly journals An Orbital Exchange Calculation of Chemical Bonding in Metals

2021 ◽  
Author(s):  
Paul Merrithew
Keyword(s):  
Electrical Properties ◽  
Continuous Flow ◽  
Chemical Bonds ◽  
Lithium Metal ◽  
Bond Energies ◽  
Exchange Method ◽  
Bond Lengths ◽  
The Difference ◽  
Beryllium Metal ◽  
Bond Direction

<p><a>This work calculates the chemical bonds in lithium metal and beryllium metal </a>using the orbital exchange method, a method that recognizes that the two electrons of a bonding pair cannot be completely distinguished when their orbitals overlap to bond. Since in metals there is no preferred bond direction, the symmetry axes of the lattice are chosen as the bonding axes. The calculations sum the primary, secondary and many tertiary bonds along these axes. <a>The bond length and bond energy results are in agreement with the observed values with bond energies accurate to 0.2 eV or better and bond lengths to 0.02Å. </a> The bond lengths are found at the point where the total bond overlap equals 1.0. </p><p> These results are compared with <a>the orbital exchange calculations of bonding in diamond, a nonconductor, and graphite, a semiconductor</a>. An uncomplicated explanation for the difference in electrical properties emerges. The conductor, lithium metal, has a 2s bonding orbital which bonds equally in both directions along all axes providing for the continuous flow of electrons. The nonconductor, diamond, has a directional s p hybrid type bonding orbital which bonds in one direction along a single axis, preventing the flow of electrons from atom to atom. </p><p> </p><p> </p><p></p>

scholarly journals An Orbital Exchange Calculation of Chemical Bonding in Metals

2021 ◽  
Author(s):  
Paul Merrithew
Keyword(s):  
Electrical Properties ◽  
Continuous Flow ◽  
Chemical Bonds ◽  
Lithium Metal ◽  
Bond Energies ◽  
Exchange Method ◽  
Bond Lengths ◽  
The Difference ◽  
Beryllium Metal ◽  
Bond Direction

<p><a>This work calculates the chemical bonds in lithium metal and beryllium metal </a>using the orbital exchange method, a method that recognizes that the two electrons of a bonding pair cannot be completely distinguished when their orbitals overlap to bond. Since in metals there is no preferred bond direction, the symmetry axes of the lattice are chosen as the bonding axes. The calculations sum the primary, secondary and many tertiary bonds along these axes. <a>The bond length and bond energy results are in agreement with the observed values with bond energies accurate to 0.2 eV or better and bond lengths to 0.02Å. </a> The bond lengths are found at the point where the total bond overlap equals 1.0. </p><p> These results are compared with <a>the orbital exchange calculations of bonding in diamond, a nonconductor, and graphite, a semiconductor</a>. An uncomplicated explanation for the difference in electrical properties emerges. The conductor, lithium metal, has a 2s bonding orbital which bonds equally in both directions along all axes providing for the continuous flow of electrons. The nonconductor, diamond, has a directional s p hybrid type bonding orbital which bonds in one direction along a single axis, preventing the flow of electrons from atom to atom. </p><p> </p><p> </p><p></p>

Molecular orbital structures of sulfones

1982 ◽  
Vol 60 (6) ◽  
pp. 730-734 ◽  
Author(s):  
Russell J. Boyd ◽  
Jeffrey P. Szabo
Keyword(s):  
Crystal Structure ◽  
Gas Phase ◽  
Molecular Orbital ◽  
Geometry Optimization ◽  
Membered Ring ◽  
Molecular Orbital Calculations ◽  
Bond Lengths ◽  
Comparison With Experiment ◽  
The Difference

Abinitio molecular orbital calculations are reported for several cyclic and acyclic sulfones. The geometries of XSO2Y, where X, Y = H, F, or CH3 are optimized at the STO-3G* level. Similar calculations are reported for the smallest cyclic sulfone, thiirane-1,1 -dioxide, as well as the corresponding sulfoxide, thiirane-1-oxide, and the parent sulfide, thiirane. Where comparison with experiment is possible, the agreement is satisfactory. In order to consider the possibility of substantial differences between axial and equatorial S—O bonds in the gas phase, as observed in the crystal structure of 5H,8H-dibenzo[d,f][1,2]-dithiocin-1,1-dioxide, STO-3G* calculations are reported for a six-membered ring, thiane-1,1-dioxide, and a model eight-membered ring. Limited geometry optimization of the axial and equatorial S—O bonds in the chair conformations of the six- and eight-membered rings leads to bond lengths of 1.46 Å with the difference being less than 0.01 Å.

Abstract 84: Atrial Fibrillation Causes a Progressive, Time-Dependent Reduction in Myocardial Neuronal NOS in Humans and Goats: Implications for AF-Induced Electrical Remodeling

2012 ◽  
Vol 111 (suppl_1) ◽  
Author(s):  
Svetlana Reilly ◽  
Xing Liu ◽  
Raja Jayaram ◽  
Sunder Verheule ◽  
Uli Schotten ◽  
...  
Keyword(s):  
Atrial Fibrillation ◽  
Electrical Properties ◽  
Tissue Concentration ◽  
Specific Effect ◽  
Right Atrial ◽  
Early Event ◽  
Atrial Myocytes ◽  
History Of ◽  
Neuronal Nos ◽  
The Difference

Rationale: Nitric oxide (NO) plays a key role in the regulation of cardiac and endothelial function and thrombogenesis. Atrial fibrillation (AF) has been associated with reduced NO availability but the mechanisms and implications of this finding remain to be fully investigated. Methods and Results: We evaluated NO synthase (NOS) activity and localization in right atrial (RA) tissue from 30 patients with permanent AF (vs. 65 controls in sinus rhythm, SR), and in the RA and left atrial (LA) tissue of 48 goats after 2 weeks (2W) and 6 months (6M) of pacing-induced AF. NOS activity was uncoupled in RA tissue from patients and goats in 6M-AF, and was caused by a reduction in BH4 tissue concentration and by an increase in arginase activity (HPLC). Although BH4 and arginine supplementation re-coupled NOS, it did not abolish the difference in NOS activity between AF and SR. Immunoblotting and immunolocalization revealed a progressive reduction in bi-atrial neuronal NOS (nNOS) protein with the duration of AF (by 65% at 2W, 86% at 6M in goats and by 62% in patients with AF) and a reduction in eNOS in long-standing AF. nNOS was reduced in atrial myocytes but not in neuronal tissue. The mRNA expression of NOS (qRT-PCR) was unaltered; however, the reduction in nNOS protein in AF was associated with an increase in nNOS ubiquitination which was partially reversed by inhibition of proteosomal activity with MG132; inhibition of the autophagy-lysosomal pathway with bafilomycin A1 did not restore nNOS protein. To investigate the electrophysiological consequences of a reduced nNOS in LA and RA myocytes, we compared electrical properties of the isolated atrial myocytes from nNOS-/- mice (n=18) and their wild type (WT) littermates after nNOS inhibition with SMTC. Both nNOS gene deletion and inhibition impaired myocytes' relaxation in both RA and LA, and result in a slower rate of decay of [Ca2+]i transient in the LA myocytes only. Conclusions: A reduction in bi-atrial nNOS activity and protein level is an early event in the natural history of AF that results in a chamber-specific effect on electrical properties of the myocytes.

Bond Energies

2008 ◽  
Author(s):  
José A. Martinho Simões ◽  
Manuel Minas da Piedade
Keyword(s):  
Driving Forces ◽  
Theoretical Models ◽  
Enthalpies Of Formation ◽  
Chemical Bonds ◽  
Bond Energies ◽  
Bond Dissociation ◽  
Dissociation Energies ◽  
Or Groups ◽  
Quantum Chemistry Calculations ◽  
Standard Enthalpies Of Formation

Although standard enthalpies of formation provide information about the net stability of molecules and their transformations, they do not always indicate stability of individual bonds. This analysis normally involves parameters, loosely called “bond energies,” that reflect the amount of energy required to cleave chemical bonds. Bond energies are essential for understanding the nature of chemical bonds. They can be used to assess the results from quantum chemistry calculations (or from other, less sophisticated theoretical models) and thus support or oppose the descriptions of those bonds. Moreover, bond energy values also enable us to estimate the driving forces of chemical reactions by considering the strengths of all the bonds that are cleaved and formed. In fact, there are many reactions for which the standard enthalpies of formation of all reactants and products are not available (and cannot be easily estimated) but whose energetics can be predicted from the appropriate bond energies. In the previous chapters, we attempted to review all the important parameters in molecular energetics, but to avoid unnecessary distraction, we deliberately omitted bond energies from the discussion. The literature is plagued with a variety of concepts that fall into that designation but are not always synonymous. We can find names like bond strengths, bond enthalpies, bond energies, bond dissociation enthalpies, bond dissociation energies, bond disruption enthalpies, bond enthalpy terms, intrinsic bond energies, and symbols like D, D̄, 〈D〉, E, BDE, and so on. The meaning of these concepts it not always obvious and, unfortunately, some are occasionally misused. Now we look into each one of them. Consider a molecule AB, where A and B can be atoms or groups of atoms.

Balance between van der Waals and coordination bond energies—Unified Model of coordination bond length in lanthanide complexes

1988 ◽  
Vol 66 (1) ◽  
pp. 109-110
Author(s):  
Xi-Zhang Feng ◽  
Ying-Ting Xu ◽  
Peng-Nian Sun
Keyword(s):  
Bond Length ◽  
Lanthanide Complexes ◽  
Morse Potential ◽  
Van Der Waals ◽  
Coordination Bond ◽  
Unified Model ◽  
Potential Well ◽  
Bond Energies ◽  
Bond Lengths

This paper presents the variation of coordination bond lengths in lanthanide complexes as a balance between van der Waals and coordination bond energies. Each coordination atom moves in a unified potential well that is a combination of the Morse potential of its coordination bond and the van der Waals potentials of its neighboring coordination atoms. This is termed the Unified Model of coordination bond length.

Isotopic Effect on the Melting Point of Lithium Nitrate

1970 ◽  
Vol 25 (5) ◽  
pp. 697-699 ◽  
Author(s):  
Bert Jansson ◽  
Arnold Lundén
Keyword(s):  
Melting Point ◽  
Isotope Effects ◽  
Zone Melting ◽  
Isotopic Effect ◽  
Lithium Nitrate ◽  
Lithium Metal ◽  
Self Diffusion ◽  
Fee Structure ◽  
The Difference ◽  
Self Diffusion Coefficient

The techniques of segregation during normal freezing and of zone melting have been used to establish that the melting point of 6LiNO3 is higher than that of 7LiNO3. The difference is of the order of 0.03 °C. The isotope shift of the melting point is in the opposite direction of the isotope effects found previously for phase transitions in solid lithium metal and lithium sulfate. For the latter salt a recalculation based on a more accurate value for the self-diffusion coefficient shows that the temperature of transition at about 575 °C to a fee structure is about 0.08 degr. lower for 6Li2SO4 than for 7Li2SO4.

scholarly journals Bond Energies and Bond Lengths

Nature ◽  
1950 ◽  
Vol 165 (4206) ◽  
pp. 908-911 ◽  
Author(s):  
H. C. LONGUET-HIGGINS
Keyword(s):  
Bond Energies ◽  
Bond Lengths

scholarly journals Capacitance of the Surface and Transverse Tubular Membrane of Frog Sartorius Muscle Fibers

1969 ◽  
Vol 53 (3) ◽  
pp. 265-278 ◽  
Author(s):  
Peter W. Gage ◽  
Robert S. Eisenberg
Keyword(s):  
Electrical Properties ◽  
Time Course ◽  
Muscle Fibers ◽  
Membrane Resistance ◽  
Ringer Solution ◽  
Sartorius Muscle ◽  
Tubular Membrane ◽  
Essentially Normal ◽  
The Difference ◽  
Passive Electrical Properties

The passive electrical properties of glycerol-treated muscle fibers, which have virtually no transverse tubules, were determined. Current was passed through one intracellular microelectrode and the time course and spatial distribution of the resulting potential displacement measured with another. The results were analyzed by using conventional cable equations. The membrane resistance of fibers without tubules was 3759 ± 331 ohm-cm2 and the internal resistivity 192 ohm-cm. Both these figures are essentially the same as those found in normal muscle fibers. The capacitance of the fibers without tubules is strikingly smaller than normal, being 2.24 ± 0.14 µF/cm2. Measurements were also made of the passive electrical properties of fibers in a Ringer solution containing 400 mM glycerol (which is used in the preparation of glycerol-treated fibers). The membrane resistance and capacitance are essentially normal, but the internal resistivity is somewhat reduced. These results show that glycerol in this concentration does not directly affect the membrane capacitance. Thus, the figure for the capacitance of glycerol-treated fibers, which agrees well with previous estimates made by different techniques, represents the capacitance of the outer membrane of the fiber. Estimates of the capacitance per unit area of the tubular membrane are made and the significance of the difference between the figures for the capacitance of the surface and tubular membrane is discussed.

(Ph4P)2 Mn2Br6 und (Ph3PCH2Ph)2Mn2I6 (Ph = C6H5) / (Ph4P)2Mn2Br6 and (Ph 3PCH2Ph)2Mn2I6 (Ph = C6H5

1988 ◽  
Vol 43 (2) ◽  
pp. 171-174 ◽  
Author(s):  
Siegfried Pohl ◽  
Wolfgang Saak ◽  
Peter Stolz
Keyword(s):  
Single Crystal ◽  
Diffraction Data ◽  
Unit Cell ◽  
Formula Unit ◽  
X Ray Diffraction ◽  
Triclinic Space Group ◽  
X Ray ◽  
Bond Lengths ◽  
The Mean ◽  
The Difference

(Ph4P)2Mn2Br6 (1) and (Ph3PCH2Ph)2Mn2I6 (2) were prepared from the reaction of manganese dihalide with the corresponding phosphonium halide in CH2Cl2.The structures of 1 and 2 were determined from single crystal X-ray diffraction data.Both compounds crystallize in the triclinic space group P 1 with one formula unit per unit cell.1:a = 998.1(1), b = 1005.7(1), c = 1313.3(2) pm, α = 108.51(1), β = 94.25(1), γ = 100.36(1)°.2: a = 1058.6(2), b = 1236.3(2), c = 1248.4(3) pm, α = 63.53(1), β = 74.15(1), γ = 74.65(1)°.The structures of 1 and 2 exhibit discrete, dimeric anions formed by the fusion of two identical tetrahedral-like units with a common halogen-halogen edge. The mean Mn-Hal bond lengths were found to be 251.8 pm (Mn-Br) and 272.2 pm (Mn-I). The difference between the bridging and terminal Mn-Hal bond lengths is about 12-13 pm in both compounds

scholarly journals AX2: Type of compounds and an overview of theoretically investigated TiO2

2020 ◽  
Vol 9 (2) ◽  
pp. 79-87
Author(s):  
Dušica Jovanović ◽  
Jelena Zagorac ◽  
Branko Matović ◽  
Aleksandra Zarubica
Keyword(s):  
Band Gap ◽  
Wide Band ◽  
Theoretical Studies ◽  
Chemical Bonds ◽  
Wide Band Gap ◽  
Specific Temperature ◽  
Temperature And Pressure ◽  
The Difference ◽  
The Stability ◽  
Experimental And Theoretical Studies

AX 2-type compounds can be ionic, covalent or molecular types of structure, which depends on the size of atoms and the polarization properties. The materials of such type of the structure have different properties that can find the application in various areas of science and industry. Titanium dioxide, as a material of AX 2-type of the structure is a wide band gap semiconductor that has been widely investigated due to its photocatalytic properties and applicability for various purposes, such as the production of solar cells, decontamination of pollutants, elimination of microorganisms, suppression of cancer cells, etc. Experimental and theoretical studies of this metal oxide can give different data on the stability of individual crystalline modifications and their transitions. This study has presented an overview of theoretically examined TiO 2 modifications and current problems that can be encountered (such as various band gap values obtained by different methods and functionals; the difference between the stability of modifications examined on ab initio level and experimentally; the character of chemical bonds and transitions at the specific temperature and pressure conditions…) and overrun by optimal corrections added in calculations.

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