The ABINIT Users Mailing List ( CLOSED )

["Aldo Humberto Romero" <aromero@qro.cinvestav.mx>]

Dear Igor,

Some advises:

did you optimize the acell?.. it does not seem like... did you try
different LDA pseudos?.. in any case, you should upgrade Abinit
to the most recent version... people is not supporting old versions
anymore. Did you check the electron occupation? in other words
did you check the warnings?

Regards

-aldo.


-> Dear abinit users,
->
-> I am having some problems while trying to reproduce the bandstructure of
-> VN in
-> its metallic rocksalt phase at ambient pressure (C. Stampfl, PRB 63,
-> 155106
-> (2001)). Specifically, I cannot calculate the closed bands at X point. I
-> always
-> get a finite opened gap.
-> I am using abinit 5.4.4p, LDA psps from the website and the following
-> input
-> file:
->
->
-> # VN rocksalt phase
-> #
-> # Computation of the band structure at about 0 GPa
-> # First, a SCF density computation, then a non-SCF band structure
-> calculation.
->
-> ndtset 2
->
-> #Dataset 1 : usual self-consistent calculation
-> kptopt1 1       # Option for the automatic generation of k points,
->                 # taking into account the symmetry
-> nshiftk1 4
-> shiftk1  0.5 0.5 0.5  # These shifts will be the same for all grids
->       0.5 0.0 0.0
->       0.0 0.5 0.0
->       0.0 0.0 0.5
-> ngkpt1        3*6
-> prtden1  1      # Print the density, for use by dataset 2
-> toldfe1  1.0d-8
-> nband1        10
->
-> #Dataset 2 : the band structure
-> iscf2         -2
-> getden2  -1
-> kptopt2  -6
-> nband2        10
-> ndivk2        15 7 12 15 15 12 # 15, 7, 12, 15, 15 and 12 divisions of 6
-> segments,
-> delimited
->                        # by 7 points
-> kptbounds2  0.0 0.0  0.0  # Gamma
->          0.5 0.0  0.5  # X
->          0.5 0.25 0.75 # W
->          0.5 0.5  0.5  # L
->          0.0 0.0  0.0  # Gamma
->          0.5 0.5  1.0  # K
->          0.5 0.0  0.5  # X
->
-> tolwfr2  1.0d-12
-> occopt        4
-> tsmear        0.04
->
-> iprcel        45
-> npulayit 10
-> nline         8
-> nnsclo        4
->
-> #Definition of the unit cell
-> acell         3*7.97
-> angdeg        90  90  90
-> spgroup  225
-> brvltt       -1
->
-> #Definition of the atom types
-> ntypat        2
-> znucl         23 7
->
-> #Definition of the atoms
-> natom 2        # There are two atoms
-> typat 1 2      # They both are of type 1, that is, Silicon.
-> 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.
->    1/2       1/2  1/2  # Triplet giving the REDUCED coordinate of atom 2.
->
-> #Definition of the planewave basis set
-> ecut 48        # Maximal kinetic energy cut-off, in Hartree
->
-> #Definition of the SCF procedure
-> nstep 100      # Maximal number of SCF cycles
->
->
->
-> I have tried to increase GS ngkpt (after 3*12 results don't change
-> anymore),
-> nband (12 gives the same results as 10) and DS2 tolwfr (10^-16 gives the
-> same
-> as 10^-12), but without success to close the gap. I am aware of the LDA
-> inappropriatness, but I thought that at least it would give the correct
-> nature
-> of the crystal.
->
-> I would appreciate any tips and corrections to my calculations.
->
-> Thank you in advance!
->
-> Igor Lukacevic
->


-- 

Prof. Aldo Humberto Romero
CINVESTAV-Unidad Queretaro
Libramiento Norponiente 2000
CP 76230, Queretaro, QRO, Mexico
tel: 442 211 9909
fax: 442 211 9938

email: aromero@qro.cinvestav.mx
        aldorome@gmail.com
www: qro.cinvestav.mx/~aromero