Dear Mash
When an scf calculation does not converge the problem is almost always
in the starting structure. In your case, you have used the lattice
parameter of alpha-Mn, which has more than 1 atom inside the unit
cell. See here, for example to look at the crystal structure
http://www.crystallography.net/cod/9011068.html
Your Mn atoms are therefore quite far from one another (around 7.7 A)
and their density does not overlap, causing your convergence
difficulties. As bcc is not the stable structure of Mn you should
guess a better (shorter) starting lattice parameter. Moreover, You may
also want to consider the fact that bcc Mn can be paramagnetic,
depending on the lattice parameter. You should therefore use nspin=2
and a meaningful value for the starting magnetization. Finally, when
you use occupations='smearing' the pw.x code add a suitable number of
unoccupied bands to ensure the stability of the calculation for
metallic systems. nband=9 might be on the scarce side: if you skip the
variable you automatically obtain 12 bands, which should ensure a
better convergence (with a meaningful lattice parameter...)
HTH
Giuseppe
Quoting Mashroor Nitol <mashroorni...@gmail.com>:
Dear Users:
I am new in QE. I want to know for which lattice parameter Manganese will
have minimum potential energy. For this the following input file is used.
But every time same error message is showing " convergence is NOT achieved
after 100 iterations: stopping. ". Can anyone help me out ?
!!!!!!!!!!!!!!!!!!!!!!!!!!! INPUT !!!!!!!!!!!!!!!!!!!!!
&control
calculation='vc-relax'
prefix='Mn_bcc_8'
restart_mode='from_scratch'
wf_collect = .false.
pseudo_dir = '/home/mash/Desktop/qe/qe-6.3/pseudo'
outdir= 'Mn_bcc_8/temp'
tprnfor = .true.
tstress = .true.
etot_conv_thr = 1.0E-5 ,
forc_conv_thr = 1.0D-4 ,
/
&system
ibrav= 3
A = 8.9125
nat= 1
ntyp= 1
ecutwfc = 37.0
ecutrho = 250.0
nbnd = 9
occupations='smearing'
smearing='methfessel-paxton'
degauss=0.005
/
&electrons
conv_thr=1d-7
/
&ions
ion_dynamics = 'bfgs'
/
&CELL
cell_dynamics = 'bfgs'
cell_dofree = 'all'
/
ATOMIC_SPECIES
Mn 54.938044 Mn.pbe-spn-kjpaw_psl.0.3.1.UPF
ATOMIC_POSITIONS {angstrom}
Mn 0.0 0.0 0.0
K_POINTS automatic
8 8 8 0 0 0
Thank you
Mash
Mississippi State University
________________
GIUSEPPE MATTIOLI
CNR - ISTITUTO DI STRUTTURA DELLA MATERIA
Via Salaria Km 29,300 - C.P. 10
I-00015 - Monterotondo Scalo (RM)
Mob (*preferred*) +39 373 7305625
Tel + 39 06 90672342 - Fax +39 06 90672316
E-mail: <giuseppe.matti...@ism.cnr.it>
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