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[张 <zhangting@pku.edu.cn>]

Dear Abinit user:
   
    I'm a beginner of abinit codes. I'm going to do some electron-
phonon coupling calculation of CNTs with the code.When I want to 
optimize the geometric configuration of (5,5) CNT,the program send me 
a warning that it can't find the cell's space group. As a result,the 
optimization job continues with maybe P1 symmetry, and consumes quite 
large memory and time. Now the job is still 
running, I'd like to know hwo to let the code find a space group 
automaticaly? and how to impose a symmetry in the cell manually? Does 
the cell have a P21/M (number 11) space group? I've set the keyword 
spgroup = 11,but it doesn't work...  I'm also afraid that if the 
single point energy is calculated with no symmetry, whether ot not the 
next phonon calculation will be reliable? For there are often 
imaginary frequencies near Gamma point in carbon systems(graphite,CNTs)
    My input file is attached.If there are any other mistakes or 
parameters unsuitable in the input file, don't hesitate to point 
out.thanks a lot 

                                                                    
Zhang Ting
                                                                    
Apr.6th 2006
# Crystalline 5_5 CNT : computation of the optimization
#

#Specific to ground state calculation
  kptopt   1            # Automatic generation of k points, taking
                        # into account the symmetry

  toldff   2.0d-8      # SCF E tolarence.when calculating the real one(not 
just testing)
    iscf   5            # Self-consistent calculation, using algorithm 5
 

#######################################################################
#Common input variables

#Definition of the unit cell

acell  25.51  25.51  4.60997932302    # a=b=13.5 A c=1.4? A                
#angdeg 90 90 120                     # alpha=90 beta=90 gamma=120
rprim  1.0    0.0          0.0        # 0.866025404 -0.500 0.0 
      -0.5    0.866025404  0.0
       0.0    0.0          1.0

#spgroup 11   #is the cell with space group 11(P21/M)? It seems no use to 
turn on it...

optcell 6     #6 opt z-direction only
ionmov  2
dilatmx 1.2   
ecutsm  0.5
tolmxf  2.0d-7
ntime   100            # BFGS steps maximum

#Definition of the atom types
ntypat 1               # There are one type of atom
znucl  6               # The keyword "znucl" refers to the atomic number of 
the 
                       # possible type(s) of atom. The pseudopotential(s) 
                       # mentioned in the "files" file must correspond
                       # to the type(s) of atom. Here, all atoms are carbon 
                       # the pseudopotential file is 6c.pspnc

#Definition of the atoms
natom 20                # There are 20 atoms
typat 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1     # All atoms are carbons.

xcart 
-1.541093 -6.257092  1.152494     
 1.131924 -6.321080  1.152494  
 2.422723 -5.936284 -1.152495
 4.636535 -4.433733 -1.152495
 5.463778 -3.371048  1.152494        
 6.358301 -0.850962  1.152494 
 6.407043  0.495587 -1.152495    
 5.699203  3.075062 -1.152495
 4.942302  4.189797  1.152494      
 2.811541  5.808595  1.152494      
 1.541093  6.257093 -1.152495    
-1.131925  6.321082 -1.152495    
-2.422723  5.936286  1.152494      
-4.636534  4.433735  1.152494      
-5.463778  3.371051 -1.152495    
-6.358301  0.850964 -1.152495    
-6.407043 -0.495585  1.152494      
-5.699203 -3.075059  1.152494      
-4.942302 -4.189795 -1.152495    
-2.811541 -5.808593 -1.152495    


#Gives the number of band, explicitely (do not take the default)
nband  48              # 20 atoms, 4 electrons per atom,80 electrons total. 
So 40 bands is enough.For metalic graphite,add 8 
                       # bands. 

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

occopt 4          # 
tsmear 0.05       # 


#Definition of the planewave basis set
ecut    36.0           # Maximal kinetic energy cut-off, in Hartree


#Definition of the k-point grid
ngkpt  2 2 10
nshiftk 1
shiftk 0.0 0.0 0.5       # ngkpt, nshiftk and shiftk .

#Definition of the SCF procedure
nstep 50               # Maximal number of SCF cycles

                       # diemac=default=1e6