Dear Christoph I suppose that you can filter out the R0 translation to obtain the autocorrelation of the dipole moment across the trajectory.
> Total 0.2108 -0.3623 0.1151 au, 0.5358 -0.9209 > 0.2925 Debye before FFT the autocorrelation function you may also try to convolute the autocorrelation function with a truncated exponential decay, an old NMR practice that will smooth your power spectrum in the frequency domain. I'm sorry but I cannot send you my old executables that have been lost in a painful hard-disk failure years ago... :-( HTH Giuseppe Quoting "Christoph Wolf(신소재공학과)" <[email protected]>: > Dear all > > > I am currently trying to calculate the IR spectrum by taking the FFT > of the Autocorrelation function obtained from a CPMD run in cp.x (QE > 6.1). > > > I recently stumbled across a post by Giuseppe Mattioli > (http://qe-forge.org/pipermail/pw_forum/2015-July/107471.html) > indicating that applying the MP correction would allow to calculate > the FFT of the AC of the dipole; hence my attempt. I obtain (for CO2 > centered inside a large empty box): > > > charge density inside the Wigner-Seitz cell: 16.00000000 > > > reference position (R0): 12.57468453 15.78158723 > 13.05433235 bohr > > > Dipole moments (with respect to x0): > > Elect 0.2108 -0.3623 0.1151 au, 0.5358 -0.9209 > 0.2925 Debye > > Ionic 0.0000 0.0000 0.0000 au, 0.0000 0.0000 > 0.0000 Debye > > Total 0.2108 -0.3623 0.1151 au, 0.5358 -0.9209 > 0.2925 Debye > > > Electrons quadrupole moment -139.68377611 a.u. > > Ions quadrupole moment 101.51494350 a.u. > > Total quadrupole moment -38.16883261 a.u. > > > ********* MAKOV-PAYNE CORRECTION ********* > > > Makov-Payne correction 0.00000000 a.u. = 0.000 eV (1st order, 1/a0) > > 0.00001738 a.u. = 0.000 eV (2nd > order, 1/a0^3) > > 0.00001738 a.u. = 0.000 eV (total) > > > corrected Total energy = -37.17673195 a.u. > > > Now a LAMMPS script (http://lammps.sandia.gov/threads/msg63251.html) > tells me that I am supposed to do the following: > > > calculate the autocorrelation function of the net dipole moment. > Compute the Fourier transform of the autocorrelation function to get > the spectrum. > > > Now I wonder which quantity to "autocorrelate". Is it > > > "Total_Dipole(timestep)+R0(timestep)" > > > Any help is greatly appreciated, especially I wonder if cppp.x is of > any help to me on my journey! Input is below (for the ion dynamics) > > > Best, > > Chris > > > Christoph Wolf, Seoul National University, Dept. of Materials > Science and Engineering > > > &control > calculation = 'cp' > title='CO2 MD' > prefix='co2', > pseudo_dir = '/home/chris/quantum_espresso/pseudo/', > outdir='./' > restart_mode='reset_counters', > nstep=8000, iprint=10, isave=10, > dt=5, > ndr=50, ndw=51 > / > &SYSTEM > ibrav = 1 > A=15 !relaxed cell value! 5.91 A > nat = 3 > ntyp = 2 > ecutwfc =80.0 > assume_isolated='mp' > / > &electrons > electron_dynamics = 'verlet' > emass=700 > / > &ions > ion_dynamics = 'verlet' > ion_temperature='nose' > fnosep=70.0 > tempw=300.0 > / > ATOMIC_SPECIES > C 12.0107 C_ONCV_PBE-Chris.UPF > O 15.999 O_ONCV_PBE-Chris.UPF > ATOMIC_POSITIONS angstrom > C 7.19147 7.73724 7.21980 > O 6.24948 7.68725 5.68537 > O 6.69993 9.42553 7.92219 -- ******************************************************** - Article premier - Les hommes naissent et demeurent libres et égaux en droits. Les distinctions sociales ne peuvent être fondées que sur l'utilité commune - Article 2 - Le but de toute association politique est la conservation des droits naturels et imprescriptibles de l'homme. Ces droits sont la liberté, la propriété, la sûreté et la résistance à l'oppression. ******************************************************** Giuseppe Mattioli CNR - ISTITUTO DI STRUTTURA DELLA MATERIA v. Salaria Km 29,300 - C.P. 10 I 00015 - Monterotondo Stazione (RM) Tel + 39 06 90672836 - Fax +39 06 90672316 E-mail: <[email protected]> http://www.ism.cnr.it/en/staff/giuseppe-mattioli/ ResearcherID: F-6308-2012 _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
