SUPPORTING INFORMATION
Various transport behaviors of zigzag
graphene nanoribbons tailoring by strain
Jinying Wang, Zhongfan Liu, and Zhirong Liu*
1 College of Chemistry and Molecular Engineering, Peking University, Beijing
100871, China
2 State Key Laboratory for Structural Chemistry of Unstable and Stable Species, and
Beijing National Laboratory for Molecular Sciences (BNLMS), Peking University,
Beijing 100871, China
*Address correspondence to: LiuZhiRong@pku.edu.cn
1. Test of the structure optimization
We performed geometry relaxations for the complete two-probe system of strained
ZGNRs using the Vienna ab initio simulation package (VASP). The projected
augmented wave (PAW) pseudopotential, and the general gradient approximation
(GGA) PW91 were used with a 520eV cutoff energy. Interactions between adjacent
sheets were avoided by using a spacing of 10Å between the sheets. A
Monkhorst-Pack grid mesh of 25×1×1 was used for ZGNRs. The energy was taken to
be converged when the difference between consecutive total energy was less than
1
0.1meV. Atoms were relaxed until the forces on the atoms were less than 0.01eV/Å.
All the atoms in the scattering region were allowed to relax in the x-direction, while
the other coordinates of atoms were fixed.
The current-voltage characteristics of the uniaxial and shear strained ZGNRs show
only small differences before and after geometry relaxation (Fig. S-1). Therefore,
structural optimization after applying strains could be neglected.
FIG. S-1. (Color online) I-Vbias characteristic of (a) shear-strained 4-ZGNR and (b)
uniaxial-strained 5-ZGNRwith structural optimization (black) and without structural
optimization (red).
2. Conductance peak at the Fermi level
We calculated the conductance spectrum of unstrained 5-ZGNR under zero bias
using different basis sets to check the accuracy of the peak at the Fermi level. The
results are summarized in Fig. S-2. The peak in the conductance spectrum has a
narrow width, and the peak height at the Fermi level decreases for the more complete
2
basis sets. Moreover, the calculated value is not an integer, which is at odds with
physical theory. This may come from the numerical nature of the calculation package
and the difficulty in automatically recognizing the exact number of energy subbands
at the Fermi level where the π and π* subbands form a degenerated flat band. Apart
from the peak at the Fermi level, the conductances at the other energy levels are
accurate. We also tested the I-Vbias characteristics of unstrained 5-ZGNRs for the three
basis sets (Fig. S-2 inset). The results show the single zeta basis set is sufficiently
accurate for our studies. Because the peak was very narrow, we excluded any further
analysis of conductance at the Fermi level and focused on the conductance spectrum
in a relatively large energy range near the Fermi level.
FIG. S-2. (Color online) Conductance spectrum of unstrained 5-ZGNR calculated by
using three basis sets: single zeta (SZT), double zeta (DZT), and double zeta polarized
(DZTP). Inset: the I-V characteristics of unstrained 5-ZGNR using the three basis
sets.
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