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[yshtogun@cas.usf.edu]

Dear ABINIT users,
I am new in ABINIT. I am trying to calculate (5.0) carbon nanotubes. My 
problem is I don't see lattice constant evidently in abinit input variables 
(in the case of carbon nanotube the lattice constant is included into 
translation vector (acell(3)-z component) and position of atoms. Does Abinitn 
work with lattice constant evidently or i have to calculate it from output 
data? Is there a way to work with lattice constant?


This is the input file I'm using:

# (5,0) Zigzag Carbon Nanotube

#Definition of the unit cell
acell 10 10 8.7494319587           # The keyword "acell" refers to the
                                   # lengths of the primitive vectors (in 
Bohr)
#Optimization of the lattice parameters
ionmov 3                                 # Use the modified Broyden algorithm
ntime 10                                 # Maximum number of Broyden 
"timesteps"

#Definition of the atom types
ntypat 1                                 # There is only one type of atom
znucl 6                               

#Definition of the atoms
natom 20                                # There are twenty atoms
typat 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1     
xangst                 # This keyword indicate that the location of the atoms
                       # will follow, one triplet of number for each atom
   1.9572176000  0.0000000000 0.0000000000   
   1.5834223000  1.1504236000 0.7100000000   
   0.6048135000  1.8614245000 0.0000000000   
  -0.6048135000  1.8614245000 0.7100000000   
  -1.5834223000  1.1504236000 0.0000000000   
  -1.9572176000 -0.0000000000 0.7100000000   
  -1.5834223000 -1.1504236000 0.0000000000   
  -0.6048135000 -1.8614245000 0.7100000000   
   0.6048135000 -1.8614245000 0.0000000000   
   1.5834223000 -1.1504236000 0.7100000000   
   1.5834223000  1.1504236000 2.1300000000   
   0.6048135000  1.8614245000 2.8400000000   
  -0.6048135000  1.8614245000 2.1300000000   
  -1.5834223000  1.1504236000 2.8400000000   
  -1.9572176000 -0.0000000000 2.1300000000   
  -1.5834223000 -1.1504236000 2.8400000000   
  -0.6048135000 -1.8614245000 2.1300000000   
   0.6048135000 -1.8614245000 2.8400000000   
   1.5834223000 -1.1504236000 2.1300000000   
   1.9572176000  0.0000000000 2.8400000000   

#Exchange-correlation functional
ixc 1                                    # LDA Teter Pade parametrization

#Definition of the planewave basis set
ecut 30.0                                # Maximal plane-wave kinetic energy  
 
                                         #cut-off, in Hartree
#Definition of the k-point grid
kptopt   1                               # Option for the automatic 
generation    
                                         #of k points, taking
                                         # into account the symmetry
#Definition of the SCF procedure
nstep 100                                # Maximal number of SCF cycles
toldfe 1.0d-6                            
diemac 12.0  


Can someone give me some advice or more information?
Any help would be greatly appreciated...

Best regards,
Yaroslav Shtogun