Quantum Signature in Anisotropic Singularities of Dihedral Energy in
Hydrogen Bond Breaking of Water Dimer
Abstract
Molecular simulations from small molecules to large bio-macromolecules
and polymer systems are routinely used to simulate thermodynamics
properties of interests by molecular mechanics-based potentials. In a
recent paper, via three different semi-empirical methods, we reported
quantum singularities in dihedral energies as signature of chemical bond
break-up process revealed under experimental X-ray as broken chemical
moieties. In this present work, applying first principle methods of
Hartree-Fock, Density Functional as well as MollerPlesset techniques we
have reconfirmed the previous general predictions of singularities in in
dihedral energies for the case of water dimer that connects two water
monomers by weak hydrogen bond. Due to quantum nature of chemical bond
breaking process leading to break-point conditions in otherwise
connected molecular topology, the singularities in dihedral energies are
also suggestive of large forces as onset in the bond-breaking process.
We have presented the details of these novel interesting findings in
this paper. These results of quantum singularities can have significant
impacts to improve current force fields and can open up new areas we
define as “Fracture Molecular Mechanics” or “Fracture Force Field”
in overlap regions of molecular and quantum mechanics based approaches
to explore and account for chemical bond-breaking mechanisms in
molecular simulation techniques.