3 research outputs found
Interlayer Potential for Homogeneous Graphene and Hexagonal Boron Nitride Systems: Reparametrization for Many-Body Dispersion Effects
A new
parametrization of the anisotropic interlayer potential for
hexagonal boron nitride (<i>h</i>-BN ILP) is presented.
The force-field is benchmarked against density functional theory calculations
of several dimer systems within the Heyd-Scuseria-Ernzerhof hybrid
density functional approximation, corrected for many-body dispersion
effects. The latter, more advanced method for treating dispersion,
is known to produce binding energies nearly twice as small as those
obtained with pairwise correction schemes, used for an earlier ILP
parametrization. The new parametrization yields good agreement with
the reference calculations to within âŒ1 and âŒ0.5 meV/atom
for binding and sliding energies, respectively. For completeness,
we present a complementary parameter set for homogeneous graphitic
systems. Together with our previously suggested ILP parametrization
for the heterogeneous graphene/<i>h</i>-BN junction, this
provides a powerful tool for consistent simulation of the structural,
mechanical, tribological, and heat transport properties of both homogeneous
and heterogeneous layered structures based on graphene and <i>h</i>-BN
Interlayer Potential for Graphene/<i>h</i>âBN Heterostructures
We present a new
force-field potential that describes the interlayer
interactions in heterojunctions based on graphene and hexagonal boron
nitride (<i>h</i>-BN). The potential consists of a long-range
attractive term and a short-range anisotropic repulsive term. Its
parameters are calibrated against reference binding and sliding energy
profiles for a set of finite dimer systems and the periodic graphene/<i>h</i>-BN bilayer, obtained from density functional theory using
a screened-exchange hybrid functional augmented by a many-body dispersion
treatment of long-range correlation. Transferability of the parametrization
is demonstrated by considering the binding energy of bulk graphene/<i>h</i>-BN alternating stacks. Benchmark calculations for the
superlattice formed when relaxing the supported periodic heterogeneous
bilayer provide good agreement with both experimental results and
previous computational studies. For a free-standing bilayer we predict
a highly corrugated relaxed structure. This, in turn, is expected
to strongly alter the physical properties of the underlying monolayers.
Our results demonstrate the potential of the developed force-field
to model the structural, mechanical, tribological, and dynamic properties
of layered heterostructures based on graphene and <i>h</i>-BN
Why Are Diphenylalanine-Based Peptide Nanostructures so Rigid? Insights from First Principles Calculations
The diphenylalanine peptide self-assembles
to form nanotubular
structures of remarkable mechanical, piezolelectrical, electrical,
and optical properties. The tubes are unexpectedly stiff, with reported
Youngâs moduli of 19â27 GPa that were extracted using
two independent techniques. Yet the physical basis for the remarkable
rigidity is not fully understood. Here, we calculate the Youngâs
modulus for bulk diphenylalanine peptide from first principles, using
density functional theory with dispersive corrections. The calculation
demonstrates that at least half of the stiffness of the material is
the result of dispersive interactions. We further quantify the nature
of various inter- and intramolecular interactions. We reveal that
despite the porous nature of the lattice, there is an array of rigid
nanotube backbones with interpenetrating âzipper-likeâ
aromatic interlocks that result in stiffness and robustness. This
presents a general strategy for the analysis of bioinspired functional
materials and may pave the way for rational design of bionanomaterials