Bond Length and Local Energy Density Property Connections for Non-Transition-Metal Oxide-Bonded Interactions

Abstract

For a variety of molecules and earth materials, the theoretical local kinetic energy density, G(r(c)), increases and the local potential energy density, V(r(c)), decreases as the M-O bond lengths (M = first- and second-row metal atoms bonded to O) decrease and the electron density, rho(r(c)), accumulates at the bond critical points, r(c). Despite the claim that the local kinetic energy density per electronic charge, G(r(c))/rho(r(c)), classifies bonded interactions as shared interactions when less than unity and closed-shell when greater, the ratio was found to increase from 0.5 to 2.5 au as the local electronic energy density, H(r(c)) = G(r(c)) + V(r(c)), decreases and becomes progressively more negative. The ratio appears to be a measure of the character of a given M-O bonded interaction, the greater the ratio, the larger the value of rho(r(c)), the smaller the coordination number of the M atom and the more shared the bonded interaction. H(r(c))/rho(r(c)) versus G(r(c))/rho(r(c)) scatter diagrams categorize the M-O bonded interactions into domains with the local electronic energy density per electron charge, H(r(c))/rho(r(c)), tending to decrease as the electronegativity differences for the bonded pairs of atoms decrease. The values of G(r(c)) and V(r(c)), estimated with a gradient-corrected electron gas theory expression and the local virial theorem, are in good agreement with theoretical values, particularly for the bonded interactions involving second-row M atoms. The agreement is poorer for shared C-O and N-O bonded interactions.

10.1007/s11445-008-2005-3

“…The positive values of ∇ 2 ρ(r) and h e (r) at the critical point (3, -1) for K(1)-O bonds indicate their predominantly electrostatic nature (interaction of the closedshell type), which is in agreement with the data in the literature for M−é bonds (M is a nontransition metal bound with oxygen) [34]. An important feature of K-O interactions is the proximity of the mean K(1)-O bond length (2.81 Å) (O is an oxygen atom of the first coor-dination sphere) and the sum of the ionic radii for seven-coordinated K + and four-coordinated O 2− (2.84 Å) [35].…”

Antibond Breaking—The Formation and Decomposition of He@Adamantane: Descriptions, Explanations, and Meaning of Concepts

“…The nearly vanishing local energy-density values of H, and the significantly positive local kinetic-energy values G/1 of 1 to 2 au, and the bond degree ratios ÀVA C H T U N G T R E N N U N G (BCP)/GA C H T U N G T R E N N U N G (BCP) of about 1.0 indicate that these interactions are neither covalent nor ionic attractive, in accordance with the chemical point of view. [39,40] …”

Anion–anion interactions: their nature, energy and role in crystal formation

“…As this value is significantly higher than that in the molecule O 2 (1.21 # A), it was concluded 110 that these two oxygen atoms are not bound to each other. The topological analysis of the electron density distribution function calculated for the crystal of silicon oxide III, however, showed 110 111 The natural mineral danburite, a borosilicate CaB 2 Si 2 O 8 , is of special interest for studies of the interactions O_O in silicates with the interatomic distance varying in a wide range, as the corresponding interatomic distances O_O are 2.3 ± 3.5 # A. 85 The peculiarities of the chemical bonding in the crystal were examined 112 by means of the periodic quantum chemical calculations.…”