Graphene nanoflakes - structural and electronic properties

Physical Review B (Impact Factor: 3.66). 02/2013; 81:085430. DOI: 10.1103/PhysRevB.81.085430
Source: arXiv

ABSTRACT The structures, cohesive energies and HOMO-LUMO gaps of graphene nanoflakes
and corresponding polycyclic aromatic hydrocarbons for a large variety of size
and topology are investigated at the density functional based tight-binding
level. Polyacene-like and honeycomb-like graphene nanoflakes were chosen as the
topological limit structures. The influence of unsaturated edge atoms and
dangling bonds on the stability is discussed. Our survey shows a linear trend
for the cohesive energy as function of Ns/N (N - total number of atoms and Ns
is number of edge atoms). For the HOMO-LUMO gap the trends are more complex and
include also the topology of the edges.

1 Bookmark
  • Carbon 02/2014; 67:721-735. · 6.16 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Graphene nanoflakes (GNFs) have more configurational degrees of freedom as compared to Graphene nanoribbons (GNRs) and are viable candidates for future nanodevices. GNFs can be devised with disparate geometries, and their electronic properties can be fine-tuned by genuine chemical functionalization. Hence, it is vital to know specific sites on GNFs where reaction is most feasible for chemical functionalization with donor− acceptor functional groups (nucleophiles/electrophiles). Here, we present spin-polarized and dispersion-corrected density functional theory based relative reactivity descriptor calculations to shed light on the reactivity pattern in small-sized GNFs. To have a clear understanding on the structure−property relationship, we consider GNFs with 24, 42, and 54 carbon atoms having various edges, namely, fully armchair, armchair/zigzag (arm-zig), and fully zigzag. All the edge atoms are saturated by hydrogen atoms. On the basis of the symmetry of the GNFs, susceptibility of assorted reactive sites pertinent to nucleophilic and electrophilic attacks is anticipated using relative reactivity descriptors. Further, we validate these relative reactivity descriptors for nucleophilic attack on armchair-C 24 H 14 and zigzag-C 24 H 12 by explicit adsorption of OH − , NH 2 − , and H 2 O molecules. Our study reveals that the reactivity pattern varies in small-sized GNFs as a function of shape. Importantly, few specific structural isomers have alternate Lewis acid−base pairs. It also manifests how the reactivity of peripheral and interior carbon atoms differ with shape and size of GNFs. With a discernment on site selectivity, GNFs can be functionalized by proper donor−acceptor groups at specific sites and hence can be used as potential candidates for molecular-and nanoelectronics.
  • [Show abstract] [Hide abstract]
    ABSTRACT: Boron and nitrogen substitutional impurities in graphene are analyzed using a self-consistent tight-binding approach. An analytical result for the impurity Green's function is derived taking broken electron-hole symmetry into account and validated by comparison to numerical diagonalization. The impurity potential depends sensitively on the impurity occupancy, leading to a self-consistency requirement. We solve this problem using the impurity Green's function and determine the self-consistent local density of states at the impurity site and, thereby, identify acceptor and donor energy resonances.
    Physical review. B, Condensed matter 04/2013; 87(15). · 3.66 Impact Factor

Full-text (2 Sources)

Available from
May 27, 2014