The ABINIT Users Mailing List ( CLOSED )

[Xavier Gonze <xavier.gonze@uclouvain.be>]

Dear Wei-Bing Zhang,

This is a bug, that has just been uncovered also in Queretaro (where  
we are having a school).
The getcell variable does not work properly for the initialization of  
the response calculations (phonon, electric field,
homogeneous electric field).
Please, do not follow the last input file of the "elastic" lesson of  
the tutorial at present.

This is easy to solve from the user's point of view.

The following will work properly : optimize the geometry of your  
system in one run, then copy by hand the
optimized geometry in another run (do not use getcell), that should  
perform the response calculations,
(so might include phonons and elastic computations). The latter run  
could do first
a very accurate determination of the density, non-self-consistent k  
point calculations, etc,
before going to response calculations.

Sorry for this.
Xavier

On 04 Apr 2008, at 11:41, Wei-Bing Zhang wrote:

> Dear abinit users!
>      I am a new user of abinit. As a test , I want to use DFFT of  
> abinit to
> calculated the elastic constants of fcc Ni. Following the example  
> provided in
> "elastic" lesson of the tutorial:, Firstly , perform a optimization  
> of acell,
> following by GS calculation. third perform a Non-self-consistent  
> GS .finally ,
> perform a RF run for symmetry-inequivalent elastic constants. And  
> the getcell
> -1 is used in last three steps.  however,  When I check the *.out,  
> I found that
> the getcell work well in step 2 and step4 but became valid in step  
> 4. in step
> 4, I found the acell is not read from the output of step 3 but come  
> from the
> input of step 1. Is "getcell" valid in RF calculations??
>    And, I cannot get reasonable elastic constant results of Ni.  
> First, i always
> get the negative constants. When I increase the "ecut" and Kpoints  
> mesh, I get
> c11  127.73978170477126  c12 97.034604419461246  c13   
> 6.812321968597402  which
> is only half of experimental value. Can you help what wrong about  
> my input
> file. How can I get the reasonable elastic results based on DFFT.  
> Thanks you.
> any suggestions about calculations of Ni will be appreciated!!
>  Wei-Bing Zhang
>  zwb256@hotmail.com
> ===================================================================
> #Al fcc metal - elastic constant calculation
>
>    ndtset   4       # Total number of datasets (3*4)
>   dilatmx=1.5
>
> # Set 1 : Initial self-consistent and lattice optimization run
>
>   getwfk1   0
>   ionmov1   2        # Broyden lattice optimization scheme
>    ntime1   50        # Maximim lattice optimization steps
>  optcell1   1        # Optimize cell volume only
>  strfact1   100      # Test convergence of stresses (Hartree/ 
> bohr^3) by
>                       # multiplying by this factor and applying force
>                       # convergence test
>   tolmxf1   1.0e-6   # Convergence limit for forces as above
>   tolvrs1   1.0d-18  # Need excellent convergence of GS quantities  
> for RF runs
> #set 2
>  prtden2   1        # Third dataset needs density
>   tolvrs2   1.0d-18
>
> # Set 3 : Converge unoccupied wave functions
>
>   getden3   -1       # Use density from previout set
>   tolwfr3   1.0d-30  # This is simply for a reason of portability  
> of automatic
> tests
>   nstep3  45
>
> # Set 4 : response-function calculations for all needed perturbations
>
>   kptopt4   2        # Time-reversal only for RF calculation
>     nqpt4   1
>      qpt4  0  0  0  # By symmetry, only need one direction
>    rfdir4   1  0  0
>   rfstrs4   3        # Need both unaxial and shear strains
>   tolvrs4   1.0d-12  # Need reasonable convergence of 1st-order  
> quantities
>
> #Common input data
>
> #Double loop data passing
>
> #getcell   -1	      # Start from optimized (datasets ?2-?4) or  
> previously
>                      # optimized (datasets ?1) acell
>  getwfk   -1	     # Use last set of wave functions (except  
> datasets ?1)
>
>
> getcell   -1
>
> nband=8
> #Definition of the plane wave basis set
>  ecutsm   0.5            # Smoothing energy needed for lattice parameter
>                          # optimization.  This will be retained for
>                          # consistency throughout.
>
> #Definition of the k-point grid - loop over 3 k-point densities
>  kptopt   1              # Use symmetry and treat only inequivalent points
>
> #ngkpt1?   6  6  6      
> ngkpt   8  8  8         
> #ngkpt3?   10 10 10
>
> nshiftk   4              # Use one copy of grid only (default)
>  shiftk   0.0 0.0 0.5    # This gives the usual fcc Monkhorst-Pack grid
>           0.0 0.5 0.0
>           0.5 0.0 0.0
>           0.5 0.5 0.5
>
> ecut 1000 eV
> #Definition of occupation numbers
> occopt 7
> tsmear 0.01
>
>
> #spin related quantities
>  spinat   0.0 0.0 1.0
>  nsppol   2
>
>
> #Definition of the unit cell
> acell 3*6.7713705382          # This is equivalent to   7.60 7.60 7.60
> rprim  0.0  0.5  0.5   # FCC primitive vectors (to be scaled by acell)
>        0.5  0.0  0.5
>        0.5  0.5  0.0
>
>
> #Definition of the atom types
> ntypat 1          # There is only one type of atom
> znucl 28          # 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.
>                         
>
> #Definition of the atoms
> natom 1           # There is only one atom per cell
> typat 1           # This atom is of type 1, that is, Aluminum
> xred              # This keyword indicate that the location of the atoms
>                   # will follow, one triplet of number for each atom
>    0.0  0.0  0.0     # Triplet giving the REDUCED coordinate of atom 1.
>
>
>
> #Exchange-correlation functional
> ixc 11             # GGA, Perdew-Burke-Ernzerhof GGA functional
>
> #Definition of the SCF procedure
> nstep 60          # Maximal number of SCF cycles
>                   # between two consecutive evaluations of total energy
>                   # differ by less than toldfe (in Hartree)
> ====================================================================== 
> ==
> == DATASET  1
> ==================================================================
>
>  Real(R)+Recip(G) space primitive vectors, cartesian coordinates
> (Bohr,Bohr^-1):
>  R(1)=	0.0000000  3.3856853  3.3856853  G(1)= -0.1476806   
> 0.1476806  0.1476806
>  R(2)=	3.3856853  0.0000000  3.3856853  G(2)=	0.1476806 -0.1476806   
> 0.1476806
>  R(3)=	3.3856853  3.3856853  0.0000000  G(3)=	0.1476806  0.1476806  
> -0.1476806
>  Unit cell volume ucvol=  7.7619305E+01 bohr^3
>  Angles (23,13,12)=  6.00000000E+01  6.00000000E+01  6.00000000E+01  
> degrees
>
>  getcut: wavevector=  0.0000  0.0000  0.0000  ngfft=  40  40  40
>          ecut(hartree)=     82.686   => boxcut(ratio)=        2.04088
> == DATASET  2
> ==================================================================
>
>  mkfilename : getwfk/=0, take file _WFK from output of DATASET   1.
>
>  driver : getcell/=0, take acell and rprim from output of dataset  
> with index
> 1.
>
>  Real(R)+Recip(G) space primitive vectors, cartesian coordinates
> (Bohr,Bohr^-1):
>  R(1)=	0.0000000  3.3857125  3.3857125  G(1)= -0.1476794   
> 0.1476794  0.1476794
>  R(2)=	3.3857125  0.0000000  3.3857125  G(2)=	0.1476794 -0.1476794   
> 0.1476794
>  R(3)=	3.3857125  3.3857125  0.0000000  G(3)=	0.1476794  0.1476794  
> -0.1476794
>  Unit cell volume ucvol=  7.7621178E+01 bohr^3
>  Angles (23,13,12)=  6.00000000E+01  6.00000000E+01  6.00000000E+01  
> degrees
>
>  getcut: wavevector=  0.0000  0.0000  0.0000  ngfft=  40  40  40
>          ecut(hartree)=     82.686   => boxcut(ratio)=        2.04086
> ---------------------------------------------------------------------- 
> ----------
>
> == DATASET  3
> ==================================================================
>
>  mkfilename : getwfk/=0, take file _WFK from output of DATASET   2.
>
>  mkfilename : getden/=0, take file _DEN from output of DATASET   2.
>
>  driver : getcell/=0, take acell and rprim from output of dataset  
> with index
> 2.
>
>  Real(R)+Recip(G) space primitive vectors, cartesian coordinates
> (Bohr,Bohr^-1):
>  R(1)=	0.0000000  3.3857125  3.3857125  G(1)= -0.1476794   
> 0.1476794  0.1476794
>  R(2)=	3.3857125  0.0000000  3.3857125  G(2)=	0.1476794 -0.1476794   
> 0.1476794
>  R(3)=	3.3857125  3.3857125  0.0000000  G(3)=	0.1476794  0.1476794  
> -0.1476794
>  Unit cell volume ucvol=  7.7621178E+01 bohr^3
>  Angles (23,13,12)=  6.00000000E+01  6.00000000E+01  6.00000000E+01  
> degrees
>
>  getcut: wavevector=  0.0000  0.0000  0.0000  ngfft=  40  40  40
>          ecut(hartree)=     82.686   => boxcut(ratio)=        2.04086
> ---------------------------------------------------------------------- 
> ----------
>
> ================================================
>
> ====================================================================== 
> ==========
> == DATASET  4
> ==================================================================
>
>  mkfilename : getwfk/=0, take file _WFK from output of DATASET   3.
>
>  driver : getcell/=0, take acell and rprim from output of dataset  
> with index
> 3.
>
>  Real(R)+Recip(G) space primitive vectors, cartesian coordinates
> (Bohr,Bohr^-1):
>  R(1)=	0.0000000  3.3856853  3.3856853  G(1)= -0.1476806   
> 0.1476806  0.1476806
>  R(2)=	3.3856853  0.0000000  3.3856853  G(2)=	0.1476806 -0.1476806   
> 0.1476806
>  R(3)=	3.3856853  3.3856853  0.0000000  G(3)=	0.1476806  0.1476806  
> -0.1476806
>  Unit cell volume ucvol=  7.7619305E+01 bohr^3
>  Angles (23,13,12)=  6.00000000E+01  6.00000000E+01  6.00000000E+01  
> degrees
>  setup1 : take into account q-point for computing boxcut.
>
>  getcut: wavevector=  0.0000  0.0000  0.0000  ngfft=  40  40  40
>          ecut(hartree)=     82.686   => boxcut(ratio)=        2.04088