The ABINIT Users Mailing List ( CLOSED )

[Gerd Steinle-Neumann <g.steinle-neumann@uni-bayreuth.de>]

Dear all --

We are trying to do linear response calculations for the conventional 
unit cell of MgO, and encounter a sunstantial problem on the way 
(probably more to come).

The goal is to move to a supercell built on the conventional cell and 
model the influence of impurities on the phonon spectrum. Obviously we 
need the pure MgO end-member to have a comparison to (a) the phonon 
spectrum for MgO from the primitive cell and (b) a baseline for the 
impurity study.

The in-file is given below.

The error we get is for the ddk computation with the following problem:

>  occeig : ERROR -
>   In a non-metallic case (occopt<3), for a RF calculation,
>   if the eigenvalues are degenerate, the occupation numbers must also 
> be degener
> ate.
>   However, the following pair of states gave :
>   k -state, band number  16, occ=    2.000000E+00, eigenvalue=    
> 3.432344E-01,
>   kq-state, band number  17, occ=    0.000000E+00, eigenvalue=    
> 3.432344E-01.
>   Action : change occopt, consistently, in GS and RF calculations.
>
>  leave_new : decision taken to exit ...
Initially we had a similar problem with the GS calculations, and were 
able to trick the code to do what we wanted by using the brvlatt 3 
option (see below). It appears that the brvlatt does not apply to the 
ddk calculation. Any idea on either (a) how we can get the code to do we 
want to do here, or (b) a completely different approach on doing this 
for the conventional cell.

Thanks, Vojtech + Gerd.

*.in-file

ndtset 2
#GS-SC
getwfk1 0
kptopt1 2
tolvrs1 1.0d-18  # from tutorial
rfphon1 0
nqpt1 0

# 2 MgO calculation - d/dk calculation
getwfk2 1
iscf2 -3
kptopt2 2
tolwfr2 1.0d-22
tolvrs2 0
rfelfd2 2
rfphon2 0
rfatpol2 1 8
rfdir2 1 1 1
#qpts
nqpt 1
    qpt2    0.00000000E+00  0.00000000E+00  0.00000000E+00


acell 3*7.89862
brvltt 3
chkprim 0
natom 8
ntypat 2
znucl 8 12
typat 1 1 1 1 2 2 2 2
nband 20             # oxygen = 6; magnesium = 2
rprim 1.0 0.0 0.0   # primitive
     0.0 1.0 0.0
     0.0 0.0 1.0
xred 0.5 0.5 0.5 
    0.5 0.5 0.0
    0.5 0.0 0.5
    0.0 0.5 0.5
    0.0 0.0 0.0
    0.5 0.0 0.0
    0.0 0.5 0.0
    0.0 0.0 0.5
ngkpt 4 4 4
nshiftk 1           # recommended in abinit tutorial
shiftk 0.5 0.5 0.5  # recommended in abinit tutorial
ecut 40

#scf
nstep 25