<div dir="ltr">Dear Stefano, <div>I actually was able to relax it using vc-relax; however, I was curious to see what happens with vc-md and vc-cp, mostly because I could set temperature with vc-md and vc-cp and not with vc-relax.</div>
<div><br></div><div>Do you think it worth trying with vc-cp? i.e. does vc-cp render more accurate structure, especially if I increase pressure?</div><div><br></div><div>Thanks in advance!</div><div><br><div class="gmail_quote">
On Thu, Oct 27, 2011 at 11:52 PM, Stefano de Gironcoli <span dir="ltr"><<a href="mailto:degironc@sissa.it">degironc@sissa.it</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<u></u>
<div bgcolor="#ffffff" text="#000000">
Dear Amin Torabi<br>
you are performing a variable-cell MD simulation therefore the
enthalpy is not minimized by the Newton equations for atoms+cell are
integrated to give you the dynamics around the target pressure (P=0
in your case).<br>
to get the relaxation you should use calculation = "vc-relax" and
then choose the minimization strategy.<br>
the default is bfgs but also damp dynamics is available.<br>
check the relevant input variables: ion_dynamics and
cell_dynamics.<br>
<br>
best regards, <br>
stefano<div><div></div><div class="h5"><br>
<br>
<br>
On 10/28/2011 02:49 AM, Amin Torabi wrote:
</div></div><blockquote type="cite"><div><div></div><div class="h5">
<pre>Dear QE users,
Will you please do me a favor and take a look at my input file, below.
The total energy and force do not converge and keep oscillating...
I have tried different dt (between 20-70) and wmass, and still not able to
relax the structure
Any comment on my the input_cards here (k-point,ecut,pp,conv...?)
Many thanks
&CONTROL
calculation = 'vc-md'
pseudo_dir = './'
outdir = './'
prefix = 'dt20'
tstress = .true
tprnfor = .true
nstep = 100
dt = 20
/
&SYSTEM
ibrav = 12
celldm(1) = 8.3147
celldm(2) = 1.3
celldm(3) = 1.4772
celldm(4) = -0.260
nat = 16
ntyp = 2
ecutwfc = 85
ecutrho = 1100
input_dft = 'pbesol'
nosym = .true
/
&ELECTRONS
conv_thr = 1.0D-9
/
&IONS
pot_extrapolation='second-order'
wfc_extrapolation='second-order'
ion_temperature = 'rescaling'
tempw = 300
/
&CELL
press = 0
cell_dynamics = 'w'
wmass = 4.2
/
ATOMIC_SPECIES
B 10.811 B.pbe-n-van.UPF
H 1.00794 H.pbe-van_bm.UPF
ATOMIC_POSITIONS crystal
B 0.005259620 0.145596712 0.040564862
H -0.199830030 0.176142715 0.150841828
H 0.217291388 0.312290957 -0.013967013
H 0.124960907 -0.022012847 0.122883862
B -0.005259620 -0.145596712 -0.040564862
H 0.199830030 -0.176142715 -0.150841828
H -0.217291388 -0.312290957 0.013967013
H -0.124960907 0.022012847 -0.122883862
B 0.494739818 0.354404554 0.540568678
H 0.699828966 0.323861788 0.650847745
H 0.282707973 0.187708799 0.486039576
H 0.375038882 0.522017144 0.622882523
B 0.505260182 0.645595446 0.459431322
H 0.300171034 0.676138212 0.349152255
H 0.717292027 0.812291201 0.513960424
H 0.624961118 0.477982856 0.377117477
K_POINTS automatic
8 8 8 0 0 0
</pre>
</div></div><pre><fieldset></fieldset>
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</blockquote>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div dir="ltr">Amin Torabi<br>Ph.D. Student<br>Chemistry Department<br>The University <i>of</i> Western Ontario<br>London, On Canada, N6A 5B7<br><span style="font-family:'Droid Sans', arial, sans-serif;font-size:13px;border-collapse:collapse;color:rgb(32, 32, 32)">Phone: <a value="+15196612111" style="color:rgb(103, 117, 58)">519-661-2111</a> Ext: 87871</span><div>
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