Hi Shoutian Sun,<br><br>With CPMD one can calculate the IR spectra by taking the fourier transform of the velocity autocorrelation function (VAF). For this, one has to run a very long simulation ( time scale few picoseconds) and then calculate the VAF. You can read a bit about VAF from any standard statistical mechanics book ( plenty of materials are available online). Also refer to the paper : <br>
<font size="2"><font size="2">J. Phys. Chem. A <b> 111</b>, 12810 (2007)
regarding the expression for the fourier transform. </font></font><br><br>Regarding your problem of tempp changing at every step, try using the nose thermostat. <br><br>Regards,<br><br>Somesh<br><br><br><div class="gmail_quote">
2009/10/6 shoutian sun <span dir="ltr"><<a href="mailto:sunshoutian168@yahoo.com.cn">sunshoutian168@yahoo.com.cn</a>></span><br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div><div style="font-family: times new roman,new york,times,serif; font-size: 12pt; color: rgb(0, 0, 0);"><div>Dear all,<br>I want to calculate IR spectrum with cp MD (cp.x) at the temperature of 100K(without elec-field).<br>
And I just make a change the input file of example30 as follows. But in the ourput file<br>the temperature value: tempp changed every step. Can anyone tell me how can I <br>calculate IR with cp MD. Thanks in advance.<br><br>
>&CONTROL<br>> calculation = 'cp',<br>> <span style="color: rgb(255, 0, 0);">restart_mode = 'from_scratch',</span><br> ><span style="color: rgb(255, 0, 0);"> nstep = 10000,</span><br>> iprint = 100,<br>
> isave = 100,<br> > tstress = .FALSE.,<br> >tprnfor = .TRUE.,<br>> <span style="color: rgb(255, 0, 0);">tefield = .TRUE., </span><br>> prefix =
'mgo',<br>> dt=5.,<br>> pseudo_dir = '/ds13/zfliu/stsun/espresso-4.1/pseudo/',<br>> outdir='/ds13/zfliu/stsun/espresso-4.1/examples/example30/results/tmp'<br>>/<br>><br>>&SYSTEM<br>
> ibrav = 1,<br>> celldm(1) = 15.912,<br>> celldm(2) = 0.0,<br>> celldm(3) = 0.0,<br>> celldm(4) = 0.0,<br> > celldm(5) = 0.0,<br> > celldm(6) = 0.0,<br>> nbnd=128,<br>> nelec=256,<br>> nat =64,<br>
> ntyp =2,<br>> ecutwfc = 40,<br>> ecutrho = 250,<br>> nr1b= 30, nr2b = 30, nr3b = 30,<br>> nspin=1,<br>>/<br>><br>>&ELECTRONS<br>> emass = 250.d0,<br>> emass_cutoff = 3.d0,<br>> electron_dynamics='damp', ortho_max=30<br>
> electron_damping=0.05<br>> startingwfc = 'random',<br>> ampre = 0.02,<br>> <span style="color: rgb(255, 0, 0);">efield = 0.0</span><br>> epol = 3<br>>/<br>><br>>&IONS<br>> ion_dynamics = 'verlet',<br>
> ion_temperature = 'rescaling',<br>> <span style="color: rgb(255, 0, 0);"> tempw = 100,</span><br>>/<br>><br>>&CELL<br> > cell_dynamics = 'none',<br>>/<br>><br>>ATOMIC_SPECIES<br>
>O 1.0 O.pz-rrkjus.UPF<br> >Mg 1.0 Mg.pz-n-vbc.UPF<br>>ATOMIC_POSITIONS (bohr)<br>>Mg 0.066300000 0.066300000 0.066300000<br>>...........<br></div></div><br>
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<br></blockquote></div><br><br clear="all"><br>-- <br>Somesh Kr. Bhattacharya<br>Post Doctoral Fellow<br>Room No. 263,<br>Leonardo Building,<br>The Abdus Salam International Centre for Theoretical Physics<br>Strada Costiera, 11<br>
I-34014 Trieste<br>Italy<br>Phone: +39-040-2240399<br>