Dear siesta users,
I have a problem with obtaining a graphene 2x2 cell (8 atoms) with
Stress-Tensor-Voigt elements less than 0.01 kBar.
The best I have managed to get is:
Stress-tensor-Voigt (kbar): 0.02 0.01 0.00
0.01 0.00 0.00
with fdf attached at the end of this email.
I was trying to obtain it with parameters
MD.VariableCell T
MD.MaxStressTol 0.001 GPa
but siesta made 1000 CG steps and did not manage to achieve a goal.
I have also discovered, that when I incerase MeshCutoff from 300 to 400
Ry the stress
tensor elements become ten times bigger. Why is that happening?
In my future work I want to replace one or more carbon atoms in my 2x2
cell with
other atoms, so I need to optimize that heterogenous cell and I am
afraid, that
it will be much more complicated problem that this with pure graphene,
so I will
appreciate any hints how to optimize pure graphene and that with other
atoms.
I will be grateful for any help and hints about my problem,
Best regards,
Peter Tempczyk
University of Warsaw
ul. Hoza 69
Pl-00-681 WARSZAWA, POLAND
SystemLabel graf
NumberOfAtoms 8
NumberOfSpecies 1
%block ChemicalSpeciesLabel
1 6 C
%endblock ChemicalSpeciesLabel
PAO.BasisSize DZP
PAO.BasisType split
kgrid_cutoff 10 Ang
MeshCutoff 300. Ry
SolutionMethod diagon # diagonalizacion. order-N. TD-DFT
MaxSCFIterations 1000 # Max. number of iterations in SCF.
DM.MixingWeight 0.1 # weight of mixing in the DM for
convergence
DM.Tolerance 1.d-3 # Tolerance in differences of DM
DM.NumberPulay 4 # Number of previous steps of DM for
mixing
ElectronicTemperature 300 K
MD.TypeOfRun CG #molecular dynamics conjugate gradients
MD.NumCGsteps 1000 # number of steps
MD.MaxForceTol 0.00001 eV/Ang
MD.MaxCGDispl 0.01 Bohr
DM.Energy.Tolerance 1.d-3 eV # Tolerance in energy
DM.Require.Harris.Convergence T
DM.Harris.Tolerance 1.d-3 eV
DM.Require.Energy.Convergence T # energia musi zejsc ponizej
zadanego poziomu!!!
WriteCoorInitial T
WriteCoorStep T # must be set true 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
WriteCoorXmol T
WriteCoorCerius T # writes final coordinats for Cerius
WriteMDCoorXmol T
WriteDM T # true is default - allows for a restart
using DM from previous run
WriteMDhistory T
WriteCoorXmol T
# 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
NetCharge 0.00
#SlabDipoleCorrection T
#SimulateDoping T
SpinPolarized F # spin polarization
xc.functional GGA # flavour of functional (LDA/GGA)
xc.authors PBE # Parametrization fos xc
WriteMullikenPop 0
WriteEigenvalues .true.
WriteWaveFunctions .true.
#inny sposob podawania parametrow
LatticeConstant 2.481807 Ang
%block LatticeParameters
2.000000 2.000000 60.0 90. 90. 60.
%endblock LatticeParameters
AtomicCoordinatesFormat NotScaledCartesianAng
%block AtomicCoordinatesAndAtomicSpecies
1.24192412 0.71702548 0.00000 1
2.48283025 1.43346309 0.00000 1
2.48282797 2.86633383 0.00000 1
3.72373434 3.58277111 0.00000 1
3.72373167 0.71702567 0.00000 1
4.96463747 1.43346348 0.00000 1
4.96463527 2.86633370 0.00000 1
6.20554162 3.58277150 0.00000 1
%endblock AtomicCoordinatesAndAtomicSpecies
AtomCoorFormatOut Ang
