# Crystalline silicon: BSE excitons with iterative diagonalization. 
ndtset 4
gwpara  2

# Definition of the planewave basis set 
ecut 6         
ecutwfn 6
ecuteps     2.1

istwfk *1
nstep  50      
diemac 12.0

# Definition of the k-point grid
kptopt 1             # Automatic generation of k points,
ngkpt  2 2 2
nshiftk 4
shiftk  0.5 0.5 0.5  
        0.5 0.0 0.0
        0.0 0.5 0.0
        0.0 0.0 0.5

########################################
# Dataset1: self-consistent calculation
########################################
tolvrs1 1.0d-12

###########################################
# Dataset2: non-self-consistent calculation
###########################################
iscf2    -2       # non self-consistency, 
getden2  -1       # read previous density file
tolwfr2  1.0d-18  
nband2    12


##############################################################
# Dataset3: 
# Build BSE Hamiltonian with model dielectric function 
# and compute bs_nstates excitons with iterative diagonalization
##############################################################
optdriver3 99
getwfk3  2
inclvkb3 2

# Parameters controlling the conjugate gradient method in the BSE code.
bs_algorithm3      3       # CG algorithm
bs_nstates3        10      # Compute first 10 eigenvectors.
tolwfr3            1.e-18  # Tolerance on residuals.
nstep3             20      # Max number of iterations
nline3             4       # Number of line minimization
nbdbuf3            4       # Exclude last 4 states from convergence test.

# Parameters for the BSE Hamiltonian.
bs_exchange_term3  1
bs_coulomb_term3   21     # Use model W and full W_GG.
mdf_epsinf3        12.0
bs_calctype3       1      # Use KS energies and orbitals to construct L0
mbpt_sciss3          0.8 eV
bs_coupling3       0
bs_loband3         2 
nband3             8


##############################################################
# Dataset4: 
# Read BSE Hamiltonian generated in the previous datasets 
# and compute bs_nstates excitons with (partial) direct diagonalization.
##############################################################
optdriver4 99
getwfk4  2
getbsreso4 3              # Read resonant block produced in dataset 4
inclvkb4  2

bs_algorithm4      1      # Direct diagonalization
bs_nstates4        10     # Compute first 10 eigenvectors --> partial diago.
bs_exchange_term4  1      # Include local fields

# Use same parameters as dataset3 for the sake of consistency although 
# H_exc will be read from file.
bs_coulomb_term4   21     # Use full W_GG read from the SCR file.
mdf_epsinf4        12.0
bs_calctype4       1      # Use KS energies and orbitals to construct L0
mbpt_sciss4          0.8 eV
bs_coupling4       0      # No coupling (default)
bs_loband4         2  
nband4             8


########################
# Crystalline structure
########################
# Definition of the unit cell: fcc
acell 3*10.217         
rprim  0.0  0.5  0.5   
       0.5  0.0  0.5
       0.5  0.5  0.0

# Definition of the atom types
ntypat 1         
znucl 14         

# Definition of the atoms
natom 2          
typat 1 1         
xred              
   0.0  0.0  0.0
   0.25 0.25 0.25

 pp_dirpath "$ABI_PSPDIR"
 pseudos "PseudosTM_pwteter/14si.pspnc"

#%%<BEGIN TEST_INFO>
#%% [setup]
#%% executable = abinit
#%% [files]
#%% files_to_test = 
#%%  t16.out,          tolnlines = 20 , tolabs = 1.1e-2, tolrel = 4.0e-2, fld_options =  -ridiculous;
#%%  t16o_DS3_EXC_MDF, tolnlines = 800, tolabs = 1.1e-2, tolrel = 4.0e-2, fld_options =  -ridiculous;
#%%  t16o_DS4_EXC_MDF, tolnlines = 800, tolabs = 1.1e-2, tolrel = 4.0e-2, fld_options =  -ridiculous;
#%% [paral_info]
#%% max_nprocs = 4
#%% [extra_info]
#%% authors = M. Giantomassi
#%% keywords = NC, GW, BSE
#%% description = 
#%%   Silicon: Computation of the excitonic levels with the Bethe-Salpeter equation.
#%%   Dataset3 uses the band-by-band conjugate gradient method to compute the lowest 10 states
#%%   Dataset4 performs the same task with partial direct diagonalization (Lapack)
#%% topics = BSE
#%%<END TEST_INFO>