Next‐generation QTAIM for scoring molecular wires in E‐fields for molecular electronic devices

Abstract

The effect of a varying, directional E x, E y, and E z electric field on the ethene molecule was investigated using next‐generation quantum theory of atoms in molecules (QTAIM). Despite using low E‐field strengths that are within the realm of experiment and do not measurably alter the molecular geometry, significant changes to the QTAIM properties were observed. Using conventional QTAIM, the shifting of the C─C and C─H bond critical points (BCPs) demonstrates polarization through an interchange in the size of the atoms involved in a bond, since a BCP is located on the boundary between a pair of bonded atoms. Next‐generation QTAIM, however, demonstrates the polarization effect more directly with a change in morphology of the 3‐D envelope around the BCP. Modest increases of ≈ 2% in the ellipticity ε of the BCP were uncovered when the C─C bond was aligned parallel or anti‐parallel to the applied E x‐field. Significant asymmetries were found in the response of the next‐generation QTAIM 3‐D paths of the C─H bonds to the applied E‐field. When the E‐field coincided with the C─C bond, the BCP moved in response and was accompanied by the envelope constructed from 3‐D next‐generation paths. The response displayed a polarization effect that increased with increasing magnitude of the E x‐field parallel and anti‐parallel to the C─C bond. Our analysis demonstrates that next‐generation QTAIM is a useful tool for understanding the response of molecules to E‐fields, for example, for the screening of molecular wires for the design of molecular electronic devices. © 2019 Wiley Periodicals, Inc.

Control of chirality, bond flexing and anharmonicity in an electric field

“…For values of the ellipticity ε > 0, the shortest and longest axes of the elliptical distribution of ρ(r b ) are associated with the λ 1 and λ 2 eigenvalues, respectively, and the ellipticity is defined as ε = jλ 1 j/jλ 2 j À 1. We earlier demonstrated that the most preferred direction for bond displacement, corresponding to most preferred direction of electronic charge density displacement, is the e 1σ eigenvector of the stress tensor [48]. Previously, we established the stress tensor trajectory T σ (s) classifications of S and R based on the counterclockwise (CCW) versus clockwise (CW) torsions for the e 1σ .dr components of T σ (s) for lactic acid and alanine [30].…”

“…In extraterrestrial regions, several molecular and ionic species in excited states generated by a strong electric field which can polarize chirality have been observed [47]. Recently, some of the current authors applied a directional (±) E ‐field on the ethene molecule and demonstrated atomic polarization of the shifted C–C and C–H BCPs [48]. The recent Perspective by Shaik et al considers the prospects of oriented external‐electric‐fields, and other electric‐field types, as “smart reagents,” for the control of reactivity and structure for chemical catalysis [49].…”

Chirality-Helicity of Cumulenes: A Non-Scalar Charge Density Derived Perspective

“…The p and q are the 3-D paths that are constructed from the values of the least (e 1 ) and most (e 2 ) preferred directions of electronic charge density accumulation along the bond-path, referred to as r . For further discussions on the construction of bond-path framework set B{p ,q ,r } [31][32][33][34][35][36][37][38][39][40][41] , see the Supplementary Materials S2 .…”

Control of Chirality, Bond flexing and Anharmonicity in an Electric Field

“…For values of the ellipticity ε > 0, the shortest and longest axes of the elliptical distribution of ρ (r b ) are associated with the λ 1 and λ 2 eigenvalues, respectively, and the ellipticity is defined as ε = |λ 1 |/|λ 2 |-1. We earlier demonstrated that the most preferred direction for bond displacement, corresponding to most preferred direction of electronic charge density displacement, is theε 1σ eigenvector of the stress tensor [48]. Previously, we established the stress tensor trajectory T σ (s ) classifications of S and R based on the counterclockwise (CCW) vs. clockwise (CW) torsions for thee 1σ .dr components of T σ (s ) for lactic acid and alanine [30].…”

“…In extraterrestrial regions, several molecular and ionic species in excited states generated by a strong electric field which can polarize chirality have been observed [47]. Recently, some of the current authors applied a directional (±)E -field on the ethene molecule and demonstrated atomic polarization of the shifted C-C and C-H bond critical points (BCPs ) [48] . The recent Perspective by Shaiket al .…”