<div dir="ltr"><div><div><div><div><div><div><div><div><div><div><div><br></div>Dear Dr. Daniele,<br><br></div> Thank you very much for your detailed reply to my question regarding Fourier interpolation for DFPT.<br><br></div> 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.<br><br></div> 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.<br><br></div>I have coupled thermo_pw.0.8.0 with QE-6.2. The script file I used is:<br><br>cat > thermo_control << EOF<br> &INPUT_THERMO<br> what='scf_disp',<br> nq1_d=128, <br> nq2_d=128, <br> nq3_d=128,<br> /<br>EOF<br>cat > <a href="http://fe.scf_disp.in">fe.scf_disp.in</a> << EOF<br> &control<br> calculation = 'scf'<br> prefix='fe',<br> pseudo_dir = '$PSEUDO_DIR/',<br> outdir='$TMP_DIR/'<br> /<br> &system<br><br>ibrav = 3, celldm(1) =5.217, nat= 1, ntyp= 1,<br> ecutwfc = 90.0,ecutrho = 1080.0,<br> occupations='smearing', smearing='marzari-vanderbilt', degauss=0.005<br> nspin = 2<br> starting_magnetization(1) = 0.5<br> /<br> &electrons<br> conv_thr = 1.0e-16,<br> mixing_beta = 0.2<br> /<br>ATOMIC_SPECIES<br> Fe 55.847 Fe.pbe-spn-rrkjus_psl.0.2.1.UPF<br>ATOMIC_POSITIONS (alat)<br> Fe 0.0 0.0 0.0<br>K_POINTS {automatic}<br> 24 24 24 1 1 1<br>EOF<br>cat > ph_control << EOF<br><br> &inputph<br> tr2_ph = 1.0e-16, <br> prefix='fe',<br> fildyn='fe.dyn',<br> ldisp=.TRUE.<br> nq1=4, nq2=4, nq3=4,<br><br>/<br>EOF<br><br></div><font size="2">With the above input the generated fe.dyn.g1.1 dynamic matrix has negative values of frequencies.<br><br></font></div><font size="2"> <span style="font-family:arial,helvetica,sans-serif">I guess I am not using the correct value of nspin. as according to pw.x input description, nspin = 2, is for:<br><br></span></font></div><font size="2"><span style="font-family:arial,helvetica,sans-serif"> spin-polarized calculation, LSDA<br></span></font></div><font size="2"><span style="font-family:arial,helvetica,sans-serif"> (manetization along z axis) <br><br></span></font></div><font size="2"><span style="font-family:arial,helvetica,sans-serif">However, for the GGA functional (</span></font><font size="2"><span style="font-family:arial,helvetica,sans-serif">Fe.pbe-spn-rrkjus_psl.0.2.1.UPF) I do not know what is the value of nspin I should be using.<br><br></span></font></div><font size="2"><span style="font-family:arial,helvetica,sans-serif">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.</span></font><br><div><div><div><div><div><div><div><div><div><div><div><div><div><br></div><div>Thanking you,<br></div><div>Best regards,<br></div><div>Krishnendu<br></div><div><br><br><br>------------------------------------------------------------------------------------------------------------------<br><br>Date: Fri, 5 Jan 2018 13:42:57 +0000<br>
From: Dragoni Daniele <<a href="mailto:daniele.dragoni@epfl.ch">daniele.dragoni@epfl.ch</a>><br>
Subject: Re: [Pw_forum] Fourier interpolation for DFPT<br>
To: PWSCF Forum <<a href="mailto:pw_forum@pwscf.org">pw_forum@pwscf.org</a>><br>
Message-ID: <<a href="mailto:1515159777313.75745@epfl.ch">1515159777313.75745@epfl.ch</a>><br>
Content-Type: text/plain; charset="iso-8859-1"<br>
<br>
Dear Krishnendu,<br>
<br>
<br>
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 <a href="http://www.fisica.uniud.it/%7Egiannozz/QE-Tutorial/tutorial_disp.html" rel="noreferrer" target="_blank">http://www.fisica.uniud.it/~<wbr>giannozz/QE-Tutorial/tutorial_<wbr>disp.html</a><br>
<br>
<br>
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 <a href="http://www.afs.enea.it/software/qu_esp/Doc/ph_6.0.0.pdf" rel="noreferrer" target="_blank">http://www.afs.enea.it/<wbr>software/qu_esp/Doc/ph_6.0.0.<wbr>pdf</a><br>
<br>
<br>
Examples of q2r and matdyn input files can be found here<br>
<br>
<a href="http://www.fisica.uniud.it/%7Egiannozz/QE-Tutorial/examples_disp.tgz" rel="noreferrer" target="_blank">http://www.fisica.uniud.it/~<wbr>giannozz/QE-Tutorial/examples_<wbr>disp.tgz</a><br>
<br>
Have also a look at this tutorial (Exercise 2 in particular)<br>
<br>
<a href="http://www.tcl.t.u-tokyo.ac.jp/pdf/2014_lm/3rd_day_pm.pdf" rel="noreferrer" target="_blank">http://www.tcl.t.u-tokyo.ac.<wbr>jp/pdf/2014_lm/3rd_day_pm.pdf</a><br>
<br>
<br>
In particular you can read:<br>
<br>
##q2r input template<br>
<br>
&INPUT<br>
fildyn = ***,<br>
flfrc = ***,<br>
zasr = ***, (we use crystal)<br>
/<br>
<br>
##<br>
<br>
<br>
## matdyn input template<br>
<br>
&INPUT<br>
ntyp = ***, (we have 1 atom type)<br>
flvec = ***,<br>
flfrc = ***,<br>
asr = ***, (we use crystal)<br>
amass(1) = ***,<br>
/<br>
*** (integer # of q points for which you want compute phonon frequencies)<br>
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)<br>
<br>
x1 x2 x3 1<br>
x1 x2 x3 2<br>
<br>
...<br>
<br>
...<br>
<br>
##<br>
<br>
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.<br>
<br>
<br>
Hope this helps!<br>
<br>
Best regards,<br>
<br>
Daniele<br>
<br>
______________________________<wbr>____________<br>
<br>
Daniele Francesco Dragoni<br>
Laboratoire de th?orie et simulation des mat?riaux<br>
Swiss Federal Institute of Technology<br>
EPFL STI IMX THEOS<br>
ME D2 1020<br>
Station 9<br>
CH-1015, Lausanne<br>
+41 21 69 31956<br>
<tel:+41216931956><br>
<br>
______________________________<wbr>__<br>
From: <a href="mailto:pw_forum-bounces@pwscf.org">pw_forum-bounces@pwscf.org</a> <<a href="mailto:pw_forum-bounces@pwscf.org">pw_forum-bounces@pwscf.org</a>> on behalf of Krishnendu Mukherjee <<a href="mailto:krishnendu.mukherjee789@gmail.com">krishnendu.mukherjee789@<wbr>gmail.com</a>><br>
Sent: Tuesday, January 2, 2018 10:31 AM<br>
To: <a href="mailto:pw_forum@pwscf.org">pw_forum@pwscf.org</a><br>
Subject: [Pw_forum] Fourier interpolation for DFPT<br>
<br>
<br>
Dear experts,<br>
<br>
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,<br>
<br>
"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."<br>
<br>
Now I gave the nq1=4, nq2=4, nq3=4 at <a href="http://fe.ph.in" rel="noreferrer" target="_blank">fe.ph.in</a><<a href="http://fe.ph.in" rel="noreferrer" target="_blank">http://fe.ph.in</a>> according to the values mentioned in the article.<br>
<br>
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.<br clear="all"><br>-- <br><div class="gmail_signature"><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div dir="ltr"><div><div>Dr. Krishnendu Mukherjee,</div></div><div><br></div><div>Principal Scientist,</div><div>CSIR-NML,</div><div>Jamshedpur.</div></div></div></div></div></div></div></div></div>
</div></div></div></div></div></div></div></div></div></div></div></div></div></div>