Hi Shoutian Sun, 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 : J. Phys. Chem. A * 111*, 12810 (2007) regarding the expression for the fourier transform.
Regarding your problem of tempp changing at every step, try using the nose thermostat. Regards, Somesh 2009/10/6 shoutian sun <sunshoutian168 at yahoo.com.cn> > Dear all, > I want to calculate IR spectrum with cp MD (cp.x) at the temperature of > 100K(without elec-field). > And I just make a change the input file of example30 as follows. But in the > ourput file > the temperature value: tempp changed every step. Can anyone tell me how can > I > calculate IR with cp MD. Thanks in advance. > > >&CONTROL > > calculation = 'cp', > > restart_mode = 'from_scratch', > > nstep = 10000, > > iprint = 100, > > isave = 100, > > tstress = .FALSE., > >tprnfor = .TRUE., > > tefield = .TRUE., > > prefix = 'mgo', > > dt=5., > > pseudo_dir = '/ds13/zfliu/stsun/espresso-4.1/pseudo/', > > outdir='/ds13/zfliu/stsun/espresso-4.1/examples/example30/results/tmp' > >/ > > > >&SYSTEM > > ibrav = 1, > > celldm(1) = 15.912, > > celldm(2) = 0.0, > > celldm(3) = 0.0, > > celldm(4) = 0.0, > > celldm(5) = 0.0, > > celldm(6) = 0.0, > > nbnd=128, > > nelec=256, > > nat =64, > > ntyp =2, > > ecutwfc = 40, > > ecutrho = 250, > > nr1b= 30, nr2b = 30, nr3b = 30, > > nspin=1, > >/ > > > >&ELECTRONS > > emass = 250.d0, > > emass_cutoff = 3.d0, > > electron_dynamics='damp', ortho_max=30 > > electron_damping=0.05 > > startingwfc = 'random', > > ampre = 0.02, > > efield = 0.0 > > epol = 3 > >/ > > > >&IONS > > ion_dynamics = 'verlet', > > ion_temperature = 'rescaling', > > tempw = 100, > >/ > > > >&CELL > > cell_dynamics = 'none', > >/ > > > >ATOMIC_SPECIES > >O 1.0 O.pz-rrkjus.UPF > >Mg 1.0 Mg.pz-n-vbc.UPF > >ATOMIC_POSITIONS (bohr) > >Mg 0.066300000 0.066300000 0.066300000 > >........... > > ------------------------------ > ?????????????????<http://cn.rd.yahoo.com/mail_cn/tagline/card/*http://card.mail.cn.yahoo.com/> > > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum > > -- Somesh Kr. Bhattacharya Post Doctoral Fellow Room No. 263, Leonardo Building, The Abdus Salam International Centre for Theoretical Physics Strada Costiera, 11 I-34014 Trieste Italy Phone: +39-040-2240399 -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20091006/8a85d31c/attachment.htm
