1 research outputs found
Nature of Lone-Pair–Surface Bonds and Their Scaling Relations
We investigate the (surface) bonding
of a class of industrially and biologically important molecules in
which the chemically active orbital is a 2<i>p</i> electron
lone pair located on an N or O atom bound via single bonds to H or
alkyl groups. This class includes water, ammonia, alcohols, ethers,
and amines. Using extensive density functional theory (DFT) calculations,
we discover scaling relations (correlations) among molecular binding
energies of different members of this class: the bonding energetics
of a single member can be used as a descriptor for other members.
We investigate the bonding mechanism for a representative (H<sub>2</sub>O) and find the most important physical surface properties that dictate
the strength and nature of the bonding through a combination of covalent
and noncovalent electrostatic effects. We describe the importance
of surface intrinsic electrostatic, geometric, and mechanical properties
in determining the extent of the lone-pair–surface interactions.
We study systems including ionic materials in which the surface positive
and negative centers create strong local surface electric fields,
which polarize the dangling lone pair and lead to a strong “electrostatically
driven bond”. We emphasize the importance of noncovalent electrostatic
effects and discuss why a fully covalent picture, common in the current
first-principles literature on surface bonding of these molecules,
is not adequate to correctly describe the bonding mechanism and energy
trends. By pointing out a completely different mechanism (charge transfer)
as the major factor for binding N- and O-containing unsaturated (radical)
adsorbates, we explain why their binding energies can be tuned independently
from those of the aforementioned species, having potential implications
in scaling-driven catalyst discovery