Chemistry Reference
In-Depth Information
In this chapter, we mainly describe the effect of external dopants of a
few novel metal clusters and electron donor or acceptor molecules on the
modification of electronic properties of a pure single layer 2D graphene
using first-principles density functional theory calculations. We consider
a few representative metal clusters of Pd, Ag, Pt and Au with 40 nu-
clearity embedded on graphene surface to model the metal nanoclusters
doping. The molecular doping on the other hand is achieved by adsorb-
ing selective donor and acceptor molecules onto the graphene surface.
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For this, we consider a few representative donor and acceptor molecules
with varying anities of electron-withdrawing and donating power. Tetra-
cyanoethylene (TCNE) and tetracyanoquinodimethane (TCNQ) have been
chosen as electron acceptors, and tetrathiafulvalene (TTF) as the electron
donor. Our study reveals that all the composite systems are stabilized
in spin-polarized ground state. The type of the deposited dopants (metal
clusters or donor/acceptor molecules) on graphene has significant effects in
changing its intriguing electronic structure. Results obtained from molec-
ular doping of graphene show that the donors and acceptors are adsorbed
on the graphene surface through a physisorption process. Mulliken popu-
lations analysis predicts that there is an effective charge transfer between
the adsorbed dopant and graphene, and its directionality follow the nature
of the adsorbed dopants. The propensity of observed interaction strength
is more for metal clusters doping compared to the molecular doping which
in fact governed by the relative extent of charge transfer between the two.
We analyze the effect of molecular charge transfer on the Raman active
phonon frequencies in graphene. The band structures together with den-
sity of states (DOS) analysis clearly show the presence of discrete localized
levels in between valence and conduction bands arising from dopants. We
too have focused on the low-frequency profile of optical conductivity of
these charge transfer complexes. Our theoretical findings
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compare fairly
well with recently reported experimental results.
43,44
2. Computational Details
The first-principles calculations are carried out using the linear combination
of atomic orbital density-functional theory (DFT) methods implemented in
the SIESTA package.
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The generalized gradient approximation (GGA) in
the Perdew-Burke-Ernzerhof (PBE) form
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polarized (DZP)
basis set are chosen for the spin-polarized DFT calculations. The inter-
action between ionic cores and valence electrons is described by norm
and double
ΞΆ
