Hi. Would you be so kind as to sign your posts, with your name and academic affiliation? MD conserves energy. It is natural that the temperature fluctuates. I am not an expert in MD, but I would also say that in order to calculate dynamical properties (such as the time correlations needed to get the IR spectrum) it is not a good idea to rescale the temperature, as "ion_temperature = 'rescaling' " seems to imply. Finally, it does not seem to me a great idea either to use MD to calculate the IR spectrum of MgO at such a low temperature. Even when when you'll have learnt all the tricks of MD, I would expect the dynamics to be very harmonic, and hence not ergodic, thus requiring long (and difficult to estimate) equilibration times. Why not using standard lattice dynamics? (vibrational frequencies + effective charges, both calculated bu "phonon"). Stefano Baroni
On Oct 6, 2009, at 2:44 AM, shoutian sun wrote: > 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 > >........... > > ????????????????? > _______________________________________________ > Pw_forum mailing list > Pw_forum at pwscf.org > http://www.democritos.it/mailman/listinfo/pw_forum --- Stefano Baroni - SISSA & DEMOCRITOS National Simulation Center - Trieste http://stefano.baroni.me [+39] 040 3787 406 (tel) -528 (fax) / stefanobaroni (skype) La morale est une logique de l'action comme la logique est une morale de la pens?e - Jean Piaget Please, if possible, don't send me MS Word or PowerPoint attachments Why? See: http://www.gnu.org/philosophy/no-word-attachments.html
