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If you know where the atoms and the cell should be, then you do not
need vc-relax (not even relax)...<br>
but the code apparently disagrees with your thoughts.<br>
trying to figure out why is probably going to increase your
understanding.<br>
have you visualized the initial and final configuration by XCrysDen
or other visualization tool?<br>
is it what you think ?<br>
<br>
stefano<br>
<br>
On 10/04/2011 11:43 AM, Ashish Kumar wrote:
<blockquote
cite="mid:CAJmZS=VCzRJ-n8fNS8JoEhc7w5jiNSeZ22ypYPxJAiP5evBWtw@mail.gmail.com"
type="cite">
<pre wrap="">Hello to all,
I have tried for the vc-relax of Mo2C hexagonal system, job is not done
properly it come out in between and the atomic positions
what I have given in the input file and what I am getting in the out file is
different.
(i) Why the crystal positions changes. what I think that the nature of the
atomic postions must be retained.
In Input file
ATOMIC_POSITIONS (alat)
C 0.00 0.00 0.00
Mo 0.3333333 0.666666 0.25
Mo 0.6666666 0.333333 0.75
In out file we get
CELL_PARAMETERS (alat= 5.67296009)
0.946518633 0.001215132 -0.004855406
-0.474470641 0.819090796 -0.000958606
0.009278926 0.007480907 1.741942673
ATOMIC_POSITIONS (alat)
C 0.156590059 0.041446237 -0.212516996
Mo 0.157761886 0.589915381 0.269109338
Mo 0.636664528 0.321113609 1.041609035
(ii) why cell_parameter changes in the out file . (I think that for
hexagonal system it must be what given in the input file)
my input file
&control
calculation='vc-relax'
restart_mode='from_scratch',
pseudo_dir = '/home/ashish/softwares/espresso/pseudo/',
outdir='/home/ashish/dft/espresso_mo2c/test1/tmp_espresso/'
prefix='mo2c'
tprnfor = .true.,
tstress = .true.
/
&system
ibrav=4, celldm(1) =5.672960087 , celldm(3)=1.573617588 , nat=3, ntyp=2,
nspin = 1, starting_magnetization(1)=0.7,
ecutwfc = 24.0, ecutrho = 288.0,
occupations='smearing', smearing='methfessel-paxton', degauss=0.02
/
&electrons
diagonalization='cg'
conv_thr = 1.0e-8
mixing_beta = 0.7
/
&ions
ion_dynamics='bfgs'
/
&cell
cell_dynamics='bfgs'
/
ATOMIC_SPECIES {crystal}
C 12.01 C.pw91-van_ak.UPF
Mo 95.94 Mo.pw91-n-van.UPF
ATOMIC_POSITIONS
C 0.0 0.0 0.0
Mo 1/3 2/3 1/4
Mo 2/3 1/3 3/4
K_POINTS automatic
4 4 4 0 0 0
can any one help me. What is the mistake (in my input file or else)
with best wishes
Ashish
</pre>
<pre wrap="">
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</blockquote>
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