Dear Dr. Daniele, Thank you very much for your detailed reply to my question regarding Fourier interpolation for DFPT.
I am trying to replicate the results of your article, "Thermoelastic properties of alpha-iron from first-principles" published in PRB 91, 104105, in 2015. I used the pseudo potential Fe.pbe-spn-rrkjus psl.0.2.1.UPF, and other values of parameter (e.g. wavefunction kinetic-energy cut off of 90 Ry etc.) as mentioned in the first two paragraphs of the section : III. COMPUTATIONAL DETAILS AND PSEUDOPOTENTIAL SELECTION. I have coupled thermo_pw.0.8.0 with QE-6.2. The script file I used is: cat > thermo_control << EOF &INPUT_THERMO what='scf_disp', nq1_d=128, nq2_d=128, nq3_d=128, / EOF cat > fe.scf_disp.in << EOF &control calculation = 'scf' prefix='fe', pseudo_dir = '$PSEUDO_DIR/', outdir='$TMP_DIR/' / &system ibrav = 3, celldm(1) =5.217, nat= 1, ntyp= 1, ecutwfc = 90.0,ecutrho = 1080.0, occupations='smearing', smearing='marzari-vanderbilt', degauss=0.005 nspin = 2 starting_magnetization(1) = 0.5 / &electrons conv_thr = 1.0e-16, mixing_beta = 0.2 / ATOMIC_SPECIES Fe 55.847 Fe.pbe-spn-rrkjus_psl.0.2.1.UPF ATOMIC_POSITIONS (alat) Fe 0.0 0.0 0.0 K_POINTS {automatic} 24 24 24 1 1 1 EOF cat > ph_control << EOF &inputph tr2_ph = 1.0e-16, prefix='fe', fildyn='fe.dyn', ldisp=.TRUE. nq1=4, nq2=4, nq3=4, / EOF With the above input the generated fe.dyn.g1.1 dynamic matrix has negative values of frequencies. I guess I am not using the correct value of nspin. as according to pw.x input description, nspin = 2, is for: spin-polarized calculation, LSDA (manetization along z axis) However, for the GGA functional (Fe.pbe-spn-rrkjus_psl.0.2.1.UPF) I do not know what is the value of nspin I should be using. So, my question is kindly let me know the value of nspin I should use. Also, if possible, please let me know if any other parameters I have input has incorrect values or needs improvement. Thanking you, Best regards, Krishnendu ------------------------------------------------------------------------------------------------------------------ Date: Fri, 5 Jan 2018 13:42:57 +0000 From: Dragoni Daniele <daniele.drag...@epfl.ch> Subject: Re: [Pw_forum] Fourier interpolation for DFPT To: PWSCF Forum <pw_forum@pwscf.org> Message-ID: <1515159777313.75...@epfl.ch> Content-Type: text/plain; charset="iso-8859-1" Dear Krishnendu, in order to perform the so-called Fourier-interpolation you need first to compute phonon frequencies with DPTF on a proper grid of q-points using ph.x. From the dynamical matrix produced by the phonon code you can then compute the interatomic force constants (IFC) in real space using the q2r.x code. From there, it is possible to recompute the phonon frequencies at any arbitrary q-point by means of the matdyn.x code. At this stage, you can specify the q-mesh (or a list of specific q-points) that is required for calculating converged values of the quantities you are interested in (in our case a 21x21x21 mesh was sufficient). For more specific information, try to have a look at this very useful document by Paolo Giannozzi http://www.fisica.uniud.it/~giannozz/QE-Tutorial/tutorial_disp.html Both q2r.x and matdyn.x should be automatically compiled by typing "make ph" from the main quantum Espresso directory, as stated (for example) here http://www.afs.enea.it/software/qu_esp/Doc/ph_6.0.0.pdf Examples of q2r and matdyn input files can be found here http://www.fisica.uniud.it/~giannozz/QE-Tutorial/examples_disp.tgz Have also a look at this tutorial (Exercise 2 in particular) http://www.tcl.t.u-tokyo.ac.jp/pdf/2014_lm/3rd_day_pm.pdf In particular you can read: ##q2r input template &INPUT fildyn = ***, flfrc = ***, zasr = ***, (we use crystal) / ## ## matdyn input template &INPUT ntyp = ***, (we have 1 atom type) flvec = ***, flfrc = ***, asr = ***, (we use crystal) amass(1) = ***, / *** (integer # of q points for which you want compute phonon frequencies) x1 x2 x3 0 (here goes a list of q points coordinates followed by a growing integer number N counting the q-points. In our case, this list should correspond to a 21x21x21 MP grid) x1 x2 x3 1 x1 x2 x3 2 ... ... ## Replace *** with the correct input card. An exhaustive description of the input cards available for the two codes can be found in the header of the source codes q2r.f90 and matdyn.f90 in /yourQEfolder/PHonon/PH directory. Hope this helps! Best regards, Daniele __________________________________________ Daniele Francesco Dragoni Laboratoire de th?orie et simulation des mat?riaux Swiss Federal Institute of Technology EPFL STI IMX THEOS ME D2 1020 Station 9 CH-1015, Lausanne +41 21 69 31956 <tel:+41216931956> ________________________________ From: pw_forum-boun...@pwscf.org <pw_forum-boun...@pwscf.org> on behalf of Krishnendu Mukherjee <krishnendu.mukherjee...@gmail.com> Sent: Tuesday, January 2, 2018 10:31 AM To: pw_forum@pwscf.org Subject: [Pw_forum] Fourier interpolation for DFPT Dear experts, I am interested in calculating the phonon calculation of bcc iron ferrite. I am following the article titled "Thermoelastic properties of alpha-iron from first-principles" authored by Daniele Dragoni, Davide Ceresoli and Nicola Marzari, published in PRB 91, 104105. In that article it is mentioned that, "Phonon calculations were carried out for each deformation within DFPT. The dynamical matrix and its eigenvalues are calculated on an 4x4x4 mesh of special points in the BZ and Fourier-interpolated on an extended 21x21x21 grid for integration of thermodynamic quantities." Now I gave the nq1=4, nq2=4, nq3=4 at fe.ph.in<http://fe.ph.in> according to the values mentioned in the article. But I do not know the parameter for which I have to set the values 21x21x21. Can you kindly let me know the parameter where I have to put the values to set the Fourier-interpolation extension grid for integration of thermodynamic quantities. -- Dr. Krishnendu Mukherjee, Principal Scientist, CSIR-NML, Jamshedpur.
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