Thank you Giuseppe for your answer. Best, Pascal
Le 29 juil. 2015 à 23:26, Giuseppe Mattioli <[email protected]> a écrit : > > Dear Pascal > If I remember well, you can obtain the cell dipole trajectory by > adding assume_isolated='mp' to your cp.x molecular dynamics input of a > system contained in a cubic cell (mp is defined for cubic cells only). > But the system should be really "isolated" (e.g., a molecule with its > center of mass always near to the center of the box) or you may have > jumps in the dipole due to PBC which should result in noise when you > FFT the dipole autocorrelation function. In my experience (an isolated > Co-oxo cluster), it was the only way to obtain an IR spectrum in a > DFT+U framework (DFPT still does not work together with DFT+U). It > should be also useful in the case of vdw corrections implemented in > cp.x. > HTH > Giuseppe > > Quoting Pascal Boulet <[email protected]>: > >> Thank you Paolo and Nicola for your answer. >> >> Best >> Pascal >> >> Le 29 juil. 2015 à 18:16, Paolo Giannozzi <[email protected]> a écrit : >> >>> From the FFTs of the atomic velocity autocorrelation function you >>> can extract phonon frequencies, but you do not get "true" spectra >>> >>> Paolo >>> >>> On Wed, Jul 29, 2015 at 6:08 PM, Pascal Boulet >>> <[email protected]> wrote: >>> Hello, >>> >>> Isn’t it possible to get IR spectra from the FFTs of the atomic >>> velocity autocorrelation function? >>> >>> Pascal >>> >>> Le 29 juil. 2015 à 17:58, Nicola Marzari <[email protected]> a écrit : >>> >>>> >>>> Dear Yin, >>>> >>>> >>>> you need to calculate at every time step the total dipole in the unit >>>> cell, and then do the fourier transform of the autocorrelation - see e.g. >>>> here: http://journals.aps.org/prl/pdf/10.1103/PhysRevLett.81.1235 or many >>>> other papers published on the topic. >>>> >>>> Note that if you do Car-Parrinello MD, rather than Born-Oppenhimer MD, >>>> the vibrational frequencies can be slightly softened due to the fact >>>> that the ions are dressed (and slowed down) by the coefficients of the >>>> plane waves. The smaller the fictitious mass, the small the effect. >>>> >>>> Now, I'm not sure how to write the polarization at every time step - >>>> maybe others can comment or add to the documentation. For PWSCF >>>> you'd switch on lberry, but I'm not sure if you can do it during an >>>> md (if now, maybe switch on lelfield, and then keep the applied field >>>> equal to zero). >>>> >>>> In CP I suppose you could switch tefield on, but still have zero >>>> applied field. >>>> >>>> Any other suggestion? Also, I think that tefield in CP and in PWSCF >>>> mean different things - shall we switch the name in CP to lelfield? >>>> >>>> nicola >>>> >>>> >>>> >>>> On 29/07/2015 15:56, [email protected] wrote: >>>>> Dear Quantum Espresso developers, >>>>> >>>>> I want to obtain IR spectra of crystals at room temperature. Considering >>>>> the temperature effect, I decided to use CPMD. I wonder whether it is >>>>> possible to get IR spectra from CPMD trajectory in Quantum Espresso? >>>>> What's more, can I involve vdw-correction in CPMD? If yes, can IR >>>>> spectra be calculated in the presence of vdw-correction? >>>>> >>>>> Thank you very much! >>>>> >>>>> Best Regards, >>>>> ------------------------------------------------------------------------ >>>>> Dr. Yin Li >>>>> Department of Biophysics,Medical School, University of Pecs, >>>>> No.12 Szigeti Street, Pecs, H-7624, HUNGARY >>>>> Phone: +36-72-535271/36271 >>>>> >>>>> >>>>> _______________________________________________ >>>>> Pw_forum mailing list >>>>> [email protected] >>>>> http://pwscf.org/mailman/listinfo/pw_forum >>>>> >>>> >>>> -- >>>> ---------------------------------------------------------------------- >>>> Prof Nicola Marzari, Chair of Theory and Simulation of Materials, EPFL >>>> Director, National Centre for Competence in Research NCCR MARVEL, EPFL >>>> http://theossrv1.epfl.ch/Main/Contact http://nccr-marvel.ch/en/project >>>> _______________________________________________ >>>> Pw_forum mailing list >>>> [email protected] >>>> http://pwscf.org/mailman/listinfo/pw_forum >>> >>> -- >>> Pascal Boulet - MCF HDR, Resp. L1 MPCI - DEPARTEMENT CHIMIE >>> Aix-Marseille Université - ST JEROME - Avenue Escadrille Normandie >>> Niemen - 13013 Marseille >>> Tél: +33(0)4 13 55 18 10 - Fax : +33(0)4 13 55 18 50 >>> Site : http://allos.up.univ-mrs.fr/pascal - Email : >>> [email protected] >>> Afin de respecter l'environnement, merci de n'imprimer cet email >>> que si nécessaire. >>> >>> >>> _______________________________________________ >>> Pw_forum mailing list >>> [email protected] >>> http://pwscf.org/mailman/listinfo/pw_forum >>> >>> >>> >>> -- >>> Paolo Giannozzi, Dept. Chemistry&Physics&Environment, >>> Univ. Udine, via delle Scienze 208, 33100 Udine, Italy >>> Phone +39-0432-558216, fax +39-0432-558222 >>> _______________________________________________ >>> Pw_forum mailing list >>> [email protected] >>> http://pwscf.org/mailman/listinfo/pw_forum >> >> -- >> Pascal Boulet - MCF HDR, Resp. L1 MPCI - DEPARTEMENT CHIMIE >> Aix-Marseille Université - ST JEROME - Avenue Escadrille Normandie >> Niemen - 13013 Marseille >> Tél: +33(0)4 13 55 18 10 - Fax : +33(0)4 13 55 18 50 >> Site : http://allos.up.univ-mrs.fr/pascal - Email : [email protected] >> Afin de respecter l'environnement, merci de n'imprimer cet email que >> si nécessaire. > > > -- > ******************************************************** > - Article premier - Les hommes naissent et demeurent > libres et ègaux en droits. Les distinctions sociales > ne peuvent être fondèes que sur l'utilitè commune > - Article 2 - Le but de toute association politique > est la conservation des droits naturels et > imprescriptibles de l'homme. Ces droits sont la libertè, > la propriètè, la sùretè et la rèsistance 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]> > > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum -- Pascal Boulet - MCF HDR, Resp. L1 MPCI - DEPARTEMENT CHIMIE Aix-Marseille Université - ST JEROME - Avenue Escadrille Normandie Niemen - 13013 Marseille Tél: +33(0)4 13 55 18 10 - Fax : +33(0)4 13 55 18 50 Site : http://allos.up.univ-mrs.fr/pascal - Email : [email protected] Afin de respecter l'environnement, merci de n'imprimer cet email que si nécessaire.
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