The single-particle momentum is studied as a tool for the visualization of the electronic regions in atoms and molecules. The limiting values of this function correctly obey two fundamental theorems: Kato's cusp condition and the Hoffmann-Ostenhof and Hoffmann-Ostenhof exponential decay. The local momentum also depicts the electron shell structure in atoms as given by its local maxima and inflection points. The integration of the electron density in a shell gives electron populations that are in agreement with the ones expected from the periodic table of the elements. The shell structure obtained is in agreement with higher level of theory computations. The average of the local kinetic energy associated with the local momentum is the Weizsäcker kinetic energy. It is shown that this quantity provides an estimate of steric interactions in molecules.
The single-particle momentum is a practical tool for the exploration of new stabilizing interactions for all kinds of molecular systems. It provides a three-dimensional representation of the molecular structure and depicts the polarizability regions, a feature not available with other continuous analyses.
A general definition of the radius of an atom in terms of its ionization energy is found. A relationship between these two fundamental properties is derived from the radial distribution function and the local momentum for the valence electrons. Strong correlations with well-known atomic radii suggest that this is a universally valid definition of the atomic radius.
The stability of peptides in the alpha-helix conformation upon replacement of the central amino acid is studied. These systems were optimized with a continuous solvent model and a recently developed DFT functional with empirical terms accounting for dispersion interactions. Both, the dispersion terms and the solvent model are directly related to the polarizability of the involved atoms. A new formula for an ab initio computation of the polarizability is introduced and tested for the amino acids.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:NSHD.ca#10222/15488 |
| Date | 18 February 2011 |
| Creators | Bohorquez, Hugo J. |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
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