Dear All, I am a new student to the field of calculation on carbon nanotube using SIESTA.I would like to have a 2unit cell optimised structure of carbonnanotube for 10-10 tube.I have already done 2 unit cell optimisation for zigzag nanotube .My procedure was as follows.
1 Geometry optimisation with mesh 250 Ry and with that optimised coordinates I
optimised mesh seeing the total energy (No geometry optimisation CG=0).In
this case I have not used any k points.
2.Then with the optimised mesh and coordinates I have started k point
optimisation(using block monkhorstpack and No geometry optimisation CG=0).Then
I found the required k points 10.Then I have done 1 k point variable
relaxation .
3.With the coordinates and lattice parameters ,I did Fixed geometry
optimisation using 10 k points.
4.Finally with the optimised coordinates I did Variable cell realxation .
Fianlly I obtained the good Density of states plot and band structures for
this unit cell relaxation..Like wise I have done optimisation for 2 unit cell
calcualtion generating the coordinates from the final variable relaxation.Here
also I obtained the good DOS and band structures.
When I was doing calcualtion for zig zag tube I observed the final pressure
for 1 unitcell fixed relaxation was -4.0569 Kbar.Then it was reduced to
-0.0004 when doing va riable cell relaxation
But When I am doing the calcualtion using the same procedure for 10-10 tube I
couldnot find any good DOS and band structure for 1 unit cell.I have not
done for 2 unitcell calcualtion.In this case pressure was -104.7488 for fixed
relaxation .
Interestingly when I tried putting 280 Mesh and 60k points for 10-10 tube
(just putting all the values in the same input file ,see the input below) I got
the very good band structures and DOS.Can I generate the coordinates for 2 Unit
cell calculation ?.Any one who has done this type of calcualtion is required to
help in this regard.
SIncerely
Kugan
#FDF file for 10-10 nanotube
#NumCG =50!!!
SystemName 10-10 tube
SystemLabel SWNT_10_10
NumberOfAtoms 40 # Number of atoms
NumberOfSpecies 1
%block ChemicalSpeciesLabel
1 6 C
%endblock ChemicalSpeciesLabel
PAO.Basis < C_Basis.fdf # contains optimized basis
# Lattice, coordinates, k-sampling
LatticeConstant 1.00 Ang
%block LatticeVectors
25.000000 0.000000 0.0000000
0.0000000 2.514900 0.0000000
0.0000000 0.000000 25.000000
%endblock LatticeVectors
%block ProjectedDensityOfStates
-20.0 10.00 0.200 500 eV
%endblock ProjectedDensityOfStates
#kgrid_cutoff 0.0 Bohr # not used as kgrid_Monkhorst_Pack is specified
%block kgrid_Monkhorst_Pack
1 0 0 0.0
0 60 0 0.0
0 0 1 0.0
%endblock kgrid_Monkhorst_Pack
WriteBands .true.
BandLinesScale ReciprocalLatticeVectors
%block BandLines
1 0.0 0.0 0.0 \Gamma
45 0.0 1.0 0.0 X
%endblock BandLines
SolutionMethod diagon
ElectronicTemperature 300.0 K # default = 300 K
AtomCoorFormatOut Ang
# DFT, Grid, SCF
XC.functional LDA # Exchange-correlation functional type
XC.authors CA # Particular parametrization of xc func
SpinPolarized F # Spin unpolarized calculation
MeshCutoff 280. Ry # Equivalent planewave cutoff for the grid
MaxSCFIterations 200 # Maximum number of SCF iterations per step
DM.MixingWeight 0.3 # New DM amount for next SCF cycle
DM.Tolerance 1.d-4 # Tolerance in maximum difference
# between input and output DM
DM.NumberPulay 3 # Number of SCF steps between pulay mixing
# Molecular dynamics and relaxations
MD.TypeOfRun cg # Type of dynamics:
MD.VariableCell F
MD.NumCGSteps 300
MD.MaxStressTol 0.02 GPa
MD.MaxForceTol 0.04 eV/Ang
MD.TargetPressure 0.00 GPa
# Output options
WriteCoorInitial T
WriteCoorStep T # must be set false to write coords at each
relax step to .ANI file
WriteForces T
WriteKpoints F
WriteEigenvalues F # use with eig2dos to plot density of states
WriteKbands F
WriteBands F
WriteMullikenPop 0 # Write Mulliken Population Analysis
WriteCoorXmol F
WriteCoorCerius F # writes final coordinats for Cerius
WriteMDCoorXmol F
WriteDM T # true is default - allows for a restart using
DM from previous run
WriteMDhistory F
WriteCoorXmol F
# Options for saving/reading information
DM.UseSaveDM T # Use DM Continuation files (use for restarting
jobs)
MD.UseSaveXV T # Use stored positions and velocities (use for
restart jobs)
UseSaveData T # useful if a restart is needed
MD.UseSaveCG T # Use stored positions and velocities
SaveRho F # Write valence pseudocharge at the mesh
SaveDeltaRho F # Write RHOscf-RHOatm at the mesh
SaveElectrostaticPotential F # Write the total elect. pot. at the mesh
SaveTotalPotential F # Write the total pot. at the mesh
WriteSiestaDim F # Write minimum dim to siesta.h and stop
WriteDenchar F # Write information for DENCHAR
AtomicCoordinatesFormat NotScaledCartesianAng
%block AtomicCoordinatesAndAtomicSpecies
9.680181 0.628716 18.833418 1
11.058592 0.628716 19.281291 1
6.496028 0.628716 15.966395 1
7.347933 0.628716 17.138942 1
5.605189 0.628716 11.775326 1
5.605189 0.628716 13.224674 1
7.347933 0.628716 7.861058 1
6.496028 0.628716 9.033605 1
11.058592 0.628716 5.718709 1
9.680181 0.628716 6.166582 1
15.319819 0.628716 6.166582 1
13.941408 0.628716 5.718709 1
18.503972 0.628716 9.033605 1
17.652067 0.628716 7.861058 1
19.394811 0.628716 13.224674 1
19.394811 0.628716 11.775326 1
17.652067 0.628716 17.138942 1
18.503972 0.628716 15.966395 1
13.941408 0.628716 19.281291 1
15.319819 0.628716 18.833418 1
9.033605 1.886184 18.503972 1
11.775326 1.886184 19.394811 1
6.166582 1.886184 15.319819 1
7.861058 1.886184 17.652067 1
5.718709 1.886184 11.058592 1
5.718709 1.886184 13.941408 1
7.861058 1.886184 7.347933 1
6.166582 1.886184 9.680181 1
11.775326 1.886184 5.605189 1
9.033605 1.886184 6.496028 1
15.966395 1.886184 6.496028 1
13.224674 1.886184 5.605189 1
18.833418 1.886184 9.680181 1
17.138942 1.886184 7.347933 1
19.281291 1.886184 13.941408 1
19.281291 1.886184 11.058592 1
17.138942 1.886184 17.652067 1
18.833418 1.886184 15.319819 1
13.224674 1.886184 19.394811 1
15.966395 1.886184 18.503972 1
%endblock AtomicCoordinatesAndAtomicSpecies
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10_10.fdf
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