Bond Flexing, Twisting, Anharmonicity and Responsivity for the IR-active
modes of Benzene
Abstract
In this investigation we have used NG-QTAIM to fully quantity the
response to the four IR-active modes of all the bonding in benzene in
terms of bond-flexing, bond-torsion and bond-anharmonicity that includes
the tendencies towards IR-responsivity and IR-non-responsivity.
Bond-anharmonicity is found to be lacking for the C-C bonds comprising
the lowest frequency mode (721.57 cm-1) measured as the absence of bond
critical point (BCP) sliding. Additionally, bond-flexing was absent for
this mode harmonic-like variation of the profile of the variation of the
wrapping (torsion) of the {p,p’} path-packet, referred to as the
Precession K, along the conventional QTAIM bond-path, the remaining
three IR-active mode possessed step-like variations in the K profiles.
The presence of non-nuclear attractors was detected for the IR-active
mode with frequency 1573.93 cm-1 with C-C K profiles that most closely
resemble those of the relaxed benzene. We quantified the C-H bonds in
terms of bond-flexing and bond-anharmonicity and IR-responsivity and
IR-non-responsivity.