<div>Dear Yansun</div>

<div> </div>

<div>Thank you !</div>

<div>Since i just use  experimental  values of the lattices, </div>

<div>i didnot  optimize the lattices and just relaxed the internal coordinates.</div>

<div> Should I optimize the lattices using "vc-relax" , and then run the ph.x calculation again ?</div>

<div> </div>

<div>Regards,</div>

<div> </div>

<div>Hai-Ping</div>

<div><br><br> </div>

<div><span class="gmail_quote">On 8/20/06, <b class="gmail_sendername">Yansun Yao</b> <<a href="mailto:yay451@mail.usask.ca">yay451@mail.usask.ca</a>> wrote:</span>

<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Dear Haiping,<br><br>     Other than the internal coordinates, did you optimize the unit cell?<br><br>     Cheers

Yansun Quoting lan haiping <<a href="mailto:lanhaiping@gmail.com">lanhaiping@gmail.com</a>>: > Dear All, > I also have calculated gamma phonon frequencies of anatase TiO2 .

> I run ph.x caculation after relaxing the structure, but  9 of 18 frequencies > are minus. > > Would you please give me some hints and help? > > input settings are below, thank you in advance !

<br>><br>> *phonons of TiO2 at Gamma<br>>  &inputph<br>>   tr2_ph=1.0d-14,<br>>   recover=.true.,<br>>   epsil=.true.,<br>>   prefix='tio2',<br>>   fildyn='TiO2-gamma.dyn',<br>>   outdir='/home/haiping/tmp/'

<br>>  /<br>> 0.0 0.0 0.0*<br>> **<br>> *Relaxing calculation input :*<br>> *&CONTROL<br>>              title = 'TiO2' ,<br>>        calculation = 'relax',<br>>          verbosity = 'default',<br>

>            tprnfor = .true.,<br>>             outdir = '/home/haiping/tmp/',<br>>             prefix = 'tio2',<br>>            disk_io = 'default',<br>>              nstep = 200,<br>>         pseudo_dir = '/home/haiping/espresso/pseudo/',

<br>> /<br>> &SYSTEM<br>>                 ibrav= 14,<br>>                celldm(1)=10.2856,celldm(2)=1.0,celldm(3)=1.0,<br>>                celldm(4)=-0.759357,celldm(5)=-0.759357,<br>>                celldm(6)=

0.518714<br>>                nat = 6 ,<br>>               ntyp = 2 ,<br>>               nbnd = 30 ,<br>>            ecutwfc = 30.0000000000,<br>>            ecutrho = 160.000,<br>>        occupations = 'fixed' ,

<br>> /<br>><br>><br>> &ELECTRONS<br>>   electron_maxstep = 100,<br>>           conv_thr = 1.0e-07,<br>>        mixing_mode = 'plain' ,<br>>        startingpot = 'atomic' ,<br>>        startingwfc = 'atomic' ,

<br>>        mixing_beta = 0.300000000,<br>>        mixing_ndim = 8,<br>>    diagonalization = 'david_overlap' ,<br>>   diago_david_ndim = 8,<br>> /<br>><br>> &IONS<br>>              ion_dynamics = 'bfgs',

<br>>              pot_extrapolation = 'first_order',<br>>              wfc_extrapolation = 'first_order',<br>><br>> /<br>><br>> ATOMIC_SPECIES<br>> O  15.999 O.pw91-van_ak.UPF<br>> Ti 47.867  Ti.pw91-nsp-van.UPF

<br>> ATOMIC_POSITIONS crystal<br>> Ti    0.00000   0.00000   0.00000<br>> Ti    0.75000   0.25000   0.50000<br>> O     0.20800   0.20800  -0.00000<br>> O     0.95800   0.45800   0.50000<br>> O     0.54200

   0.04200   0.50000<br>> O     0.79200   0.79200  -0.00000<br>> K_POINTS   automatic<br>> 6 6 7   0 0 0<br>><br>> *<br>><br>><br>> On 8/19/06, Ezad Shojaee <<a href="mailto:ezadshojaee@hotmail.com">

ezadshojaee@hotmail.com</a>> wrote:<br>> ><br>> > hi<br>> > i am trying to calculate phonon frequencies at gamma point of<br>> > TiO2(anatase)<br>> > and i have relaxed the structure enough (i think )but performing 

PH.Xafter<br>> > scf, 2of 18 frequencies  are minus!<br>> > i want to know that what technical problem do i have? does anyone<br>> > calculate<br>> > these beore?<br>> > any suggestion will be appreciated

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