The ABINIT Users Mailing List ( CLOSED )

[deyulu@yahoo.com]

Dear Abinit users:
     I have a question regarding the convergence on the unoccupied states in 
GW calculations. In the GW tutorial, I saw two different ways to compute KSS 
files.

1. compute all the bands within the SCF (e.g.: tgw_1.in), and save to KSS.
2. compute ground state density in the 1st dataset and perform a 
non-self-consistent calculation using the converged density to obtain the KSS 
file.
    In the second aproach, one can normaly set "tolwfr" to control the 
convergence. In the first one, however, I couldn't find a criteria to control 
the non-self-consistent steps in SCF. After a look in vtowfk.F90, it seems to 
me that within one SCF, the number of non-self-consistent loop (nnsclo_now) 
is often to be 1 or 2. 
    If it is true, does it mean that we should NOT use the 1st approach to 
generate KSS file, since the unoccupied states are unlikely to be converged?
    There is another issue related to this. I'm testing the band/FFT 
parallelization of Abinit5.4.3 on powerpc-ibm-aix5.2.0.0 machines. While the 
it works fine for the SCF calculations, "segmentation fault" errors occurred 
in non-self-consistent calculations with "iscf=-2". Below are my hostname.ac 
file and input file.

    Best
    Deyu Lu


***************************************************************************
Deyu Lu (Ph.D)

190 Chemistry Building
University of California, Davis 
One Shields Avenue
Davis, CA 95616
Office phone: (530) 754-9663
Group Webpage: http://angstrom.ucdavis.edu/

***************************************************************************

----------------------------host.ac----------------------------------------
CC=/usr/bin/cc
FC=mpxlf90_r
with_mpi_fc=mpxlf90_r
TRUE_CPPFLAGS=" "
enable_64bit_flags="yes"
with_mpi_fcflags="-O2 -qarch=pwr4 -qtune=pwr4 -qcache=auto -qstrict 
-qsuppress=1520-022:1520-031"
with_fc_optflags="-O2 -qarch=pwr4 -qtune=pwr4 -qcache=auto -qstrict 
-qsuppress=1520-022:1520-031"
with_mpi_cppflags="-DSCALAPACK -DMPI_FFT"
enable_fc_wrapper="yes"
enable_mpi="yes"
with_mpi_prefix=/usr/lpp/ppe.poe
with_mpi_run=/usr/lpp/ppe.poe/bin/mpiexec
enable_linalg="yes"
with_linalg_ldflags="-L../../linalg -lblas -L/usr/local/apps/scalapack 
-lscalapack -L/usr/local/apps/LAPACK -llapack -lessl"

----------------------------tgw_1.in-------------------------------------
# Crystalline silicon
# Calculation of the GW corrections
# Dataset 1: ground state calculation and of the kss file for 10 k-points in 
IBZ
# Dataset 2: calculation of the screening (epsilon^-1 matrix for W)
# Dataset 3: calculation of the Self-Energy matrix elements (GW corrections)

ndtset      1
jdtset      1
istwfk      1

npband 4 npfft 1
timopt -1
fftalg 401 wfoptalg 4 fft_opt_lob 2
iprcch 0 intxc 0


# Definition of parameters for the calculation of the KSS file
nband1      40         # Number of (occ and empty) bands to be computed
prtden1     1

# non-self consistent calculation of bands
iscf2    -2             # Non self-consistent calculation
getden2  -1             # Read previous density file
tolwfr2  1.0d-12        # Still get it converged
nband2   200

# Data common to the three different datasets
enunit      1
prteig      1

# Definition of the unit cell: fcc
acell  3*10.217        # This is equivalent to   10.217 10.217 10.217
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 14          # 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, the only type is Silicon.

# Definition of the atoms
natom 2           # There are two atoms
typat  1 1        # They both are of type 1, that is, Silicon.
xred              # Reduced coordinate of atoms
      0.0  0.0  0.0
      0.25 0.25 0.25


# Definition of the k-point grid
nkpt    1

# Use only symmorphic operations
symmorphi 0

# Definition of the planewave basis set (at convergence 16 Rydberg 8 Hartree)
ecut 8.0          # Maximal kinetic energy cut-off, in Hartree

# Definition of the SCF procedure
nstep   50        # Maximal number of SCF cycles
toldfe  1.0d-6    # Will stop when this tolerance is achieved on total energy
diemac  12.0      # Although this is not mandatory, it is worth to
                  # precondition the SCF cycle. The model dielectric
                  # function used as the standard preconditioner
                  # is described in the "dielng" input variable section.
                  # Here, we follow the prescription for bulk silicon.