An Orbital Exchange Calculation of Chemical Bonding in Metals

<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>

An Orbital Exchange Calculation of Chemical Bonding in Metals

<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>

Extreme-Modulation of Liquid Crystal Viscoelasticity via Altering Ester Bond Direction

The understanding of correlations between molecular-details and macroscopic material behaviors is a fundamental question of molecular chemistry/physics and offers practical interests in material design with fine-property-tunability. Herein, we demonstrate extreme...

Mulliken-Dipole Population Analysis

Atomic charge is one of the most important concepts in Chemistry. Mulliken population analysis is historically the most important method to calculate atomic charges and is still widely used. One basic hypothesis of this method is the half-and-half partition of the overlap populations, Q(μ, <i>v</i>), into equal charges in orbitals μ and <i>v</i>. This partition preserves the monopole moment of the overlap density but, other than that, is arbitrary. In this work we derive a new population analysis (which we designate Mulliken-Dipole population analysis) based on the conservation of both the monopole moment and the dipole moment along the bond direction. Test calculations show that the Mulliken-Dipole atomic charges are in accord to the chemical intuition; also they are very different from the Mulliken ones, being quite similar to the Hirshfeld atomic charges. Mulliken-Dipole atomic charges are conceptually appealing and very easy to calculate. In a further step, we also show how this Mulliken-Dipole population analysis can be used to derive atomic charges for atomistic simulations that reproduce the total dipole moment of the molecule, yielding at the same time a good description of the local charges and dipole moments for the molecular fragments.<br>

Mulliken-Dipole Population Analysis

Atomic charge is one of the most important concepts in Chemistry. Mulliken population analysis is historically the most important method to calculate atomic charges and is still widely used. One basic hypothesis of this method is the half-and-half partition of the overlap populations, Q(μ, <i>v</i>), into equal charges in orbitals μ and <i>v</i>. This partition preserves the monopole moment of the overlap density but, other than that, is arbitrary. In this work we derive a new population analysis (which we designate Mulliken-Dipole population analysis) based on the conservation of both the monopole moment and the dipole moment along the bond direction. Test calculations show that the Mulliken-Dipole atomic charges are in accord to the chemical intuition; also they are very different from the Mulliken ones, being quite similar to the Hirshfeld atomic charges. Mulliken-Dipole atomic charges are conceptually appealing and very easy to calculate. In a further step, we also show how this Mulliken-Dipole population analysis can be used to derive atomic charges for atomistic simulations that reproduce the total dipole moment of the molecule, yielding at the same time a good description of the local charges and dipole moments for the molecular fragments.<br>

Cylindrical macrocyclic compounds synthesized by connecting two bowl-shaped calix[3]aramide moieties: structures and chiroptical properties

Chiral macrocyclic compounds whose absolute configurations were derived from the amide bond direction were synthesized by homo coupling of meta-calix[3]aramide derivatives.

Use of Electronic Stress Tensor Density and Energy Density in Chemistry

The concepts of electronic stress tensor density and energy density give new viewpoints for conventional ideas in chemistry. In this paper, we introduce the electronic stress tensor and energy density and other related quantities such as tension density and kinetic energy density, which are based on quantum field theory, and show their connection to the concepts in chemistry. The topics are: (i) zero surface of the electronic kinetic energy density and size of atoms, (ii) separatrix of the tension field as a boundary surface of atoms in a molecule, (iii) interpretation of energy density based bond order as directional derivative of a total energy of a molecule regarding the bond direction, and (iv) eigenvalues of the stress tensor as tools to classify types of chemical bond.