15: (5,0) Carbon Nanotube Transport properties¶
Note that these systems require reasonably large-scale electronic structure calculations.
Bulk Transport properties¶
-
Outline: Obtain the quantum conductance of a pristine single-walled carbon nanotube
-
Directory:
tutorials/tutorial14/periodic
Files can be downloaded fron here -
Input Files
-
cnt.scf
Thepwscf
input file for ground state calculation -
cnt.nscf
Thepwscf
input file to obtain Bloch states for the conduction states -
cnt.pw2wan
Input file forpw2wannier90
-
cnt.win
Thewannier90
input file
-
First we consider a single unit cell, with 10 k-points. With
transport_mode = bulk
we compute the transport properties of a
pristine, infinite, periodic (5,0) carbon nanotube. Later, we will
compare the quantum conductance of this system with a defected nanotube.
-
Run
pwscf
andwannier90
. -
The quantum conductance and density of states are written to the files
cnt_qc.dat
andcnt_dos.dat
, respectively.
LCR transport properties Defected nanotube¶
-
Outline: Use the automated LCR routine to investigate the effect of a single silicon atom in a infinite (5,0) carbon nanotube.
-
Directory:
tutorials/tutorial15/defected
Files can be downloaded from here -
Input Files
-
cnt+si.scf
Thepwscf
input file for ground state calculation -
cnt+si.nscf
Thepwscf
input file to obtain Bloch states for the conduction states -
cnt+si.pw2wan
Input file forpw2wannier90
-
cnt+si.win
Thewannier90
input file
-
In this calculation an 11-atom supercell is used with a single silicon substitutional defect in the central unit cell. The supercell is chosen so that is conforms to the 2c2 geometry (see User Guide for details) with principal layers set to be two unit cells long.
-
Run
pwscf
andwannier90
. Again these are large calculations, progress can be monitored by viewing respective output files. -
The quantum conductance is written to
cnt+si_qc.dat
. Compare the quantum conductance with the periodic (bulk) calculation. Your plot should look like this{reference-type="ref" reference="fig:cnt_qc"}.
Further ideas¶
-
Set
write_hr = true
in the bulk case. Consider the magnitude of Hamiltonian elements between Wannier functions in increasingly distant unit cells. Are two unit cell principal layers really large enough, or are significant errors introduced? -
Does one unit cell either side of the defected unit cell shield the disorder so that the leads are ideal? Does the quantum conductance change if these 'buffer' regions are increased?