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I believe Eyvaz is correct, for anatase use:<br>
<br>
ibrav = 7<br>
A choice of cartesian coordinates for measured values:<br>
Ti (0,0,0)<br>
Ti (0,a/2,c/4)<br>
O (0,0,-uc)<br>
O (0,0,+uc)<br>
O (0,a/2,c/4-uc)<br>
O (0,a/2,c/4+uc)<br>
<br>
where a = 3.785, c=9.514, u=.2081<br>
<br>
Luke<br>
<a class="moz-txt-link-abbreviated" href="mailto:eyvaz_isaev@yahoo.com">eyvaz_isaev@yahoo.com</a> wrote:
<blockquote cite="mid20060820145956.23780.qmail@web60312.mail.yahoo.com" type="cite">
<pre wrap="">OK, let me hint more.
Anatase has a Pearson symbol tI12 or space group
I4_1/amd. So, ibrav should be 7, but you have chosen a
monoclinic lattice, i.e. ibrav=14. The space group has
16 symmetry elements, but your choice after correcting
ecutrho gives only 4 symmetry elements .
Imagine FCC lattice and its conventional basis
vectors now. According to you now we have to put
ibrav=4 or 5. But ibrav=2 for FCC lattice.
In addition, I also checked your input file via
XCrysDen before I replied previously. Yes, there is no
problem with it, but a figure does not look like
anatase though you used nonzero ibrav. XcrysDen
usually replicates atomic positions if ibrav.neq.0.
For example, if you put ibrav=0 for FCC cell and
specify conventional CELL_PARAMETERS you will find a
rhombohedron, but using ibrav=2 and default basis
vectors you find a cubic cell.
Bests,
Eyvaz.
--- lan haiping <a class="moz-txt-link-rfc2396E" href="mailto:lanhaiping@gmail.com"><lanhaiping@gmail.com></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Dear Eyvaz,
Thank you.
I checked the strcuture again using XCRYSDEN,
and found no problems related to the lattices.
Regards,
Hai-Ping
On 8/20/06, Eyvaz Isaev <a class="moz-txt-link-rfc2396E" href="mailto:eyvaz_isaev@yahoo.com"><eyvaz_isaev@yahoo.com></a>
wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hi,
It seems your lattice choice is not correct.
</pre>
</blockquote>
<pre wrap="">Please
</pre>
<blockquote type="cite">
<pre wrap="">have a look at
<a class="moz-txt-link-freetext" href="http://cst-www.nrl.navy.mil/lattice/struk/c5.html">http://cst-www.nrl.navy.mil/lattice/struk/c5.html</a>
Bests,
Eyvaz.
--- lan haiping <a class="moz-txt-link-rfc2396E" href="mailto:lanhaiping@gmail.com"><lanhaiping@gmail.com></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Dear All,
I also have calculated gamma phonon frequencies
</pre>
</blockquote>
</blockquote>
<pre wrap="">of
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">anatase TiO2 .
I run ph.x caculation after relaxing the
</pre>
</blockquote>
</blockquote>
<pre wrap="">structure,
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">but 9 of 18 frequencies
are minus.
Would you please give me some hints and help?
input settings are below, thank you in advance !
*phonons of TiO2 at Gamma
&inputph
tr2_ph=1.0d-14,
recover=.true.,
epsil=.true.,
prefix='tio2',
fildyn='TiO2-gamma.dyn',
outdir='/home/haiping/tmp/'
/
0.0 0.0 0.0*
**
*Relaxing calculation input :*
*&CONTROL
title = 'TiO2' ,
calculation = 'relax',
verbosity = 'default',
tprnfor = .true.,
outdir = '/home/haiping/tmp/',
prefix = 'tio2',
disk_io = 'default',
nstep = 200,
pseudo_dir =
'/home/haiping/espresso/pseudo/',
/
&SYSTEM
ibrav= 14,
celldm(1)=10.2856,celldm(2)=1.0,celldm(3)=1.0,
celldm(4)=-0.759357,celldm(5)=-0.759357,
celldm(6)=0.518714
nat = 6 ,
ntyp = 2 ,
nbnd = 30 ,
ecutwfc = 30.0000000000,
ecutrho = 160.000,
occupations = 'fixed' ,
/
&ELECTRONS
electron_maxstep = 100,
conv_thr = 1.0e-07,
mixing_mode = 'plain' ,
startingpot = 'atomic' ,
startingwfc = 'atomic' ,
mixing_beta = 0.300000000,
mixing_ndim = 8,
diagonalization = 'david_overlap' ,
diago_david_ndim = 8,
/
&IONS
ion_dynamics = 'bfgs',
pot_extrapolation = 'first_order',
wfc_extrapolation = 'first_order',
/
ATOMIC_SPECIES
O 15.999 O.pw91-van_ak.UPF
Ti 47.867 Ti.pw91-nsp-van.UPF
ATOMIC_POSITIONS crystal
Ti 0.00000 0.00000 0.00000
Ti 0.75000 0.25000 0.50000
O 0.20800 0.20800 -0.00000
O 0.95800 0.45800 0.50000
O 0.54200 0.04200 0.50000
O 0.79200 0.79200 -0.00000
K_POINTS automatic
6 6 7 0 0 0
*
On 8/19/06, Ezad Shojaee
</pre>
</blockquote>
</blockquote>
<pre wrap=""><a class="moz-txt-link-rfc2396E" href="mailto:ezadshojaee@hotmail.com"><ezadshojaee@hotmail.com></a>
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">wrote:
</pre>
<blockquote type="cite">
<pre wrap="">hi
i am trying to calculate phonon frequencies at
</pre>
</blockquote>
<pre wrap="">gamma point of
</pre>
<blockquote type="cite">
<pre wrap="">TiO2(anatase)
and i have relaxed the structure enough (i
</pre>
</blockquote>
</blockquote>
</blockquote>
<pre wrap="">think
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">)but performing PH.Xafter
</pre>
<blockquote type="cite">
<pre wrap="">scf, 2of 18 frequencies are minus!
i want to know that what technical problem do
</pre>
</blockquote>
</blockquote>
</blockquote>
<pre wrap="">i
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">have? does anyone
</pre>
<blockquote type="cite">
<pre wrap="">calculate
these beore?
any suggestion will be appreciated
</pre>
</blockquote>
</blockquote>
</blockquote>
</blockquote>
<pre wrap=""><!---->
--- lan haiping <a class="moz-txt-link-rfc2396E" href="mailto:lanhaiping@gmail.com"><lanhaiping@gmail.com></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Dear Eyvaz,
Thank you.
I checked the strcuture again using XCRYSDEN,
and found no problems related to the lattices.
Regards,
Hai-Ping
On 8/20/06, Eyvaz Isaev <a class="moz-txt-link-rfc2396E" href="mailto:eyvaz_isaev@yahoo.com"><eyvaz_isaev@yahoo.com></a>
wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Hi,
It seems your lattice choice is not correct.
</pre>
</blockquote>
<pre wrap="">Please
</pre>
<blockquote type="cite">
<pre wrap="">have a look at
<a class="moz-txt-link-freetext" href="http://cst-www.nrl.navy.mil/lattice/struk/c5.html">http://cst-www.nrl.navy.mil/lattice/struk/c5.html</a>
Bests,
Eyvaz.
--- lan haiping <a class="moz-txt-link-rfc2396E" href="mailto:lanhaiping@gmail.com"><lanhaiping@gmail.com></a> wrote:
</pre>
<blockquote type="cite">
<pre wrap="">Dear All,
I also have calculated gamma phonon frequencies
</pre>
</blockquote>
</blockquote>
<pre wrap="">of
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">anatase TiO2 .
I run ph.x caculation after relaxing the
</pre>
</blockquote>
</blockquote>
<pre wrap="">structure,
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">but 9 of 18 frequencies
are minus.
Would you please give me some hints and help?
input settings are below, thank you in advance !
*phonons of TiO2 at Gamma
&inputph
tr2_ph=1.0d-14,
recover=.true.,
epsil=.true.,
prefix='tio2',
fildyn='TiO2-gamma.dyn',
outdir='/home/haiping/tmp/'
/
0.0 0.0 0.0*
**
*Relaxing calculation input :*
*&CONTROL
title = 'TiO2' ,
calculation = 'relax',
verbosity = 'default',
tprnfor = .true.,
outdir = '/home/haiping/tmp/',
prefix = 'tio2',
disk_io = 'default',
nstep = 200,
pseudo_dir =
'/home/haiping/espresso/pseudo/',
/
&SYSTEM
ibrav= 14,
celldm(1)=10.2856,celldm(2)=1.0,celldm(3)=1.0,
celldm(4)=-0.759357,celldm(5)=-0.759357,
celldm(6)=0.518714
nat = 6 ,
ntyp = 2 ,
nbnd = 30 ,
ecutwfc = 30.0000000000,
ecutrho = 160.000,
occupations = 'fixed' ,
/
&ELECTRONS
electron_maxstep = 100,
conv_thr = 1.0e-07,
mixing_mode = 'plain' ,
startingpot = 'atomic' ,
startingwfc = 'atomic' ,
mixing_beta = 0.300000000,
mixing_ndim = 8,
diagonalization = 'david_overlap' ,
diago_david_ndim = 8,
/
&IONS
ion_dynamics = 'bfgs',
pot_extrapolation = 'first_order',
wfc_extrapolation = 'first_order',
/
ATOMIC_SPECIES
O 15.999 O.pw91-van_ak.UPF
Ti 47.867 Ti.pw91-nsp-van.UPF
ATOMIC_POSITIONS crystal
Ti 0.00000 0.00000 0.00000
Ti 0.75000 0.25000 0.50000
O 0.20800 0.20800 -0.00000
O 0.95800 0.45800 0.50000
O 0.54200 0.04200 0.50000
O 0.79200 0.79200 -0.00000
K_POINTS automatic
6 6 7 0 0 0
*
On 8/19/06, Ezad Shojaee
</pre>
</blockquote>
</blockquote>
<pre wrap=""><a class="moz-txt-link-rfc2396E" href="mailto:ezadshojaee@hotmail.com"><ezadshojaee@hotmail.com></a>
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">wrote:
</pre>
<blockquote type="cite">
<pre wrap="">hi
i am trying to calculate phonon frequencies at
</pre>
</blockquote>
<pre wrap="">gamma point of
</pre>
<blockquote type="cite">
<pre wrap="">TiO2(anatase)
and i have relaxed the structure enough (i
</pre>
</blockquote>
</blockquote>
</blockquote>
<pre wrap="">think
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">)but performing PH.Xafter
</pre>
<blockquote type="cite">
<pre wrap="">scf, 2of 18 frequencies are minus!
i want to know that what technical problem do
</pre>
</blockquote>
</blockquote>
</blockquote>
<pre wrap="">i
</pre>
<blockquote type="cite">
<blockquote type="cite">
<pre wrap="">have? does anyone
</pre>
<blockquote type="cite">
<pre wrap="">calculate
these beore?
any suggestion will be appreciated
</pre>
</blockquote>
</blockquote>
</blockquote>
</blockquote>
<pre wrap=""><!---->_________________________________________________________________
</pre>
<blockquote type="cite">
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<blockquote type="cite">
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</pre>
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