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<p>Hello,</p>
<p>first thing, I would plot the phonon dispersion sat each volume
to verify that they are actually nice and positive. If you have
internal degrees of freedom, and you did not relax them, it is
likely that you got negative phonons, which definitely breaks QHA
(more or less catastrophically, depending on how you do it).<br>
</p>
<p>cheers<br>
</p>
<div class="moz-cite-prefix">On 06/11/2022 16:40, Jakob Kraus wrote:<br>
</div>
<blockquote type="cite"
cite="mid:82fdeeb6-d97e-bdeb-910c-06d63eb85010@physik.tu-freiberg.de">Dear
QE users,
<br>
<br>
<br>
thank you very much for your comments.
<br>
<br>
To clarify: I am indeed trying to work with the QHA, and the
diagrams with the oscillations I talked about show F(V,T) + pV as
a function of V for a given temperature.
<br>
<br>
The system in the input files is a cubic insulator, and I
calculate the phonon contributions in F(V,T) with the help of the
phonon DOS as generated by successive application of
<br>
<br>
ph.x, q2r.x, and matdyn.x. The combination of total energy and
phononic contributions is done with the help of the ASE
CrystalThermo functionality.
<br>
<br>
The calculations for the series of volumes currently use the same
rescaled cubic unit cell, with matching rescaled atomic positions.
<br>
<br>
I will try the cell_dofree='shape' option and keep you updated. If
you have further suggestions, feel free to add!
<br>
<br>
<br>
Best regards,
<br>
<br>
<br>
Jakob
<br>
<br>
<br>
Am 06.11.2022 um 12:00 schrieb
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Today's Topics:
<br>
<br>
1. oscillations in G(V) diagrams (Jakob Kraus)
<br>
2. Re: oscillations in G(V) diagrams (Lorenzo Bastonero)
<br>
3. Re: oscillations in G(V) diagrams (Lorenzo Paulatto)
<br>
<br>
<br>
----------------------------------------------------------------------
<br>
<br>
Message: 1
<br>
Date: Fri, 4 Nov 2022 09:20:27 +0100
<br>
From: Jakob Kraus <a class="moz-txt-link-rfc2396E" href="mailto:jakob.kraus@physik.tu-freiberg.de"><jakob.kraus@physik.tu-freiberg.de></a>
<br>
To: <a class="moz-txt-link-abbreviated" href="mailto:users@lists.quantum-espresso.org">users@lists.quantum-espresso.org</a>
<br>
Subject: [QE-users] oscillations in G(V) diagrams
<br>
Message-ID:
<br>
<a class="moz-txt-link-rfc2396E" href="mailto:68c7ecda-68e4-bf8b-68af-ea7d030635f8@physik.tu-freiberg.de"><68c7ecda-68e4-bf8b-68af-ea7d030635f8@physik.tu-freiberg.de></a>
<br>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
<br>
<br>
Dear QE users,
<br>
<br>
<br>
I am trying to calculate heat capacities, and to this end, I
have
<br>
calculated the Gibbs energy as a function of volume
<br>
<br>
at several temperatures in a range of 0-700 K.
<br>
<br>
However, the functions that result from this do not show a
single
<br>
minimum, but rather a whole lot of oscillations, which
<br>
<br>
seem to originate from the phonons, since the E(V) diagram at 0
K shows
<br>
a single minimum as expected.
<br>
<br>
I am thankful for any help you can offer with getting rid of
these
<br>
oscillations.
<br>
<br>
I have attached input files and some plots to showcase the
problem.
<br>
<br>
<br>
Best regards,
<br>
<br>
<br>
Jakob Kraus, TU Freiberg
<br>
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<br>
&input
<br>
fildyn = 'matdyn'
<br>
zasr = 'crystal'
<br>
flfrc = 'force.fc'
<br>
/
<br>
-------------- next part --------------
<br>
&CONTROL
<br>
calculation = 'scf'
<br>
title = 'Zr_BH4_4_v95'
<br>
verbosity = 'high'
<br>
restart_mode = 'from_scratch'
<br>
tstress = .true.
<br>
tprnfor = .true.
<br>
outdir = './'
<br>
prefix = 'espresso'
<br>
pseudo_dir = '/home/kraus/pslibrary_pp/PBE_PAW'
<br>
/
<br>
&SYSTEM
<br>
ibrav = 1
<br>
ecutwfc = 120
<br>
ecutrho = 960
<br>
occupations = 'fixed'
<br>
nspin = 1
<br>
ntyp = 3
<br>
nat = 21
<br>
celldm(1) = 11.718963054402725
<br>
/
<br>
&ELECTRONS
<br>
electron_maxstep = 300
<br>
conv_thr = 1e-10
<br>
mixing_beta = 0.7
<br>
/
<br>
<br>
ATOMIC_SPECIES
<br>
Zr 91.224 Zr.pbe-spn-kjpaw_psl.1.0.0.UPF
<br>
B 10.81 B.pbe-n-kjpaw_psl.1.0.0.UPF
<br>
H 1.008 H.pbe-kjpaw_psl.1.0.0.UPF
<br>
<br>
K_POINTS automatic
<br>
2 2 2 0 0 0
<br>
<br>
ATOMIC_POSITIONS angstrom
<br>
Zr 3.1007040770 3.1007040770 3.1007040770
<br>
B 4.4131080846 1.7883000693 1.7883000693
<br>
B 1.7883000693 4.4131080846 1.7883000693
<br>
B 1.7883000693 1.7883000693 4.4131080846
<br>
B 4.4131080846 4.4131080846 4.4131080846
<br>
H 3.2091046915 1.6105056976 1.6105056976
<br>
H 2.9923034624 4.5909024564 1.6105056976
<br>
H 2.9923034624 1.6105056976 4.5909024564
<br>
H 3.2091046915 4.5909024564 4.5909024564
<br>
H 1.6105056976 3.2091046915 1.6105056976
<br>
H 1.6105056976 2.9923034624 4.5909024564
<br>
H 4.5909024564 2.9923034624 1.6105056976
<br>
H 4.5909024564 3.2091046915 4.5909024564
<br>
H 1.6105056976 1.6105056976 3.2091046915
<br>
H 4.5909024564 1.6105056976 2.9923034624
<br>
H 1.6105056976 4.5909024564 2.9923034624
<br>
H 4.5909024564 4.5909024564 3.2091046915
<br>
H 5.0910460240 1.1103621300 1.1103621300
<br>
H 1.1103621300 5.0910460240 1.1103621300
<br>
H 1.1103621300 1.1103621300 5.0910460240
<br>
H 5.0910460240 5.0910460240 5.0910460240
<br>
<br>
-------------- next part --------------
<br>
phdos Zr_BH4_4
<br>
&INPUTPH
<br>
tr2_ph = 1.D-14
<br>
prefix = 'espresso'
<br>
outdir = './'
<br>
fildyn = 'matdyn'
<br>
ldisp = .true.
<br>
nq1 = 3
<br>
nq2 = 3
<br>
nq3 = 3
<br>
/
<br>
-------------- next part --------------
<br>
&input
<br>
asr = 'crystal'
<br>
flfrc = 'force.fc'
<br>
dos = .true.
<br>
fldos = 'matdyn.dos'
<br>
deltaE = 1
<br>
nk1 = 20
<br>
nk2 = 20
<br>
nk3 = 20
<br>
/
<br>
<br>
------------------------------
<br>
<br>
Message: 2
<br>
Date: Sat, 5 Nov 2022 16:55:49 +0100
<br>
From: Lorenzo Bastonero <a class="moz-txt-link-rfc2396E" href="mailto:lbastone@uni-bremen.de"><lbastone@uni-bremen.de></a>
<br>
To: Quantum ESPRESSO users Forum
<a class="moz-txt-link-rfc2396E" href="mailto:users@lists.quantum-espresso.org"><users@lists.quantum-espresso.org></a>
<br>
Subject: Re: [QE-users] oscillations in G(V) diagrams
<br>
Message-ID:
<a class="moz-txt-link-rfc2396E" href="mailto:1FAE10D0-D7D7-442A-937C-A5ADD90C107B@uni-bremen.de"><1FAE10D0-D7D7-442A-937C-A5ADD90C107B@uni-bremen.de></a>
<br>
Content-Type: text/plain; charset="us-ascii"
<br>
<br>
Dear Jakob,
<br>
<br>
Do you mean the Helmoltz free energy (F)?
<br>
<br>
As by definition, the Gibbs free energy (G) does not depend upon
volume, but on pressure and temperature.
<br>
At p=0, then they are the same, but notice always that:
<br>
<br>
G(p,T) = min_{V}[F(V, T)+pV]
<br>
<br>
Thus, at p=0, you still need to take the minimum of F at the
fixed temperature.
<br>
<br>
Moreover, I guess you are using the quasi-harmonic
approximation. There exist several flavours. Unless your system
is isotropic, scaling the volume isotropically can be a source
of error (due to a physical assumption, not due to the
numerics).
<br>
<br>
Best,
<br>
Lorenzo Bastonero
<br>
<br>
********************************
<br>
Lorenzo Bastonero
<br>
<br>
PhD Student
<br>
U Bremen Excellence Chair,
<br>
Bremen Center for Computational Materials Science,
<br>
and MAPEX Center for Materials and Processes
<br>
<br>
University of Bremen
<br>
Faculty of Production Engineering
<br>
TAB-Building, Room 3.32
<br>
Am Fallturm 1
<br>
28359 Bremen, DE
<br>
<br>
<a class="moz-txt-link-freetext" href="http://www.hmi.uni-bremen.de/">http://www.hmi.uni-bremen.de/</a>
<br>
<br>
<blockquote type="cite">Il giorno 4 nov 2022, alle ore 09:20,
Jakob Kraus <a class="moz-txt-link-rfc2396E" href="mailto:jakob.kraus@physik.tu-freiberg.de"><jakob.kraus@physik.tu-freiberg.de></a> ha
scritto:
<br>
<br>
Dear QE users,
<br>
<br>
<br>
I am trying to calculate heat capacities, and to this end, I
have calculated the Gibbs energy as a function of volume
<br>
<br>
at several temperatures in a range of 0-700 K.
<br>
<br>
However, the functions that result from this do not show a
single minimum, but rather a whole lot of oscillations, which
<br>
<br>
seem to originate from the phonons, since the E(V) diagram at
0 K shows a single minimum as expected.
<br>
<br>
I am thankful for any help you can offer with getting rid of
these oscillations.
<br>
<br>
I have attached input files and some plots to showcase the
problem.
<br>
<br>
<br>
Best regards,
<br>
<br>
<br>
Jakob Kraus, TU Freiberg
<br>
<G_Zr_BH4_0.0.png><E_Zr_BH4.png><espresso.qi><espresso.pwi><espresso.phi><espresso.mdi>_______________________________________________
<br>
The Quantum ESPRESSO community stands by the Ukrainian
<br>
people and expresses its concerns about the devastating
<br>
effects that the Russian military offensive has on their
<br>
country and on the free and peaceful scientific, cultural,
<br>
and economic cooperation amongst peoples
<br>
_______________________________________________
<br>
Quantum ESPRESSO is supported by MaX (<a class="moz-txt-link-abbreviated" href="http://www.max-centre.eu">www.max-centre.eu</a>)
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users mailing list <a class="moz-txt-link-abbreviated" href="mailto:users@lists.quantum-espresso.org">users@lists.quantum-espresso.org</a>
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<br>
------------------------------
<br>
<br>
Message: 3
<br>
Date: Sat, 5 Nov 2022 22:09:31 +0100
<br>
From: Lorenzo Paulatto <a class="moz-txt-link-rfc2396E" href="mailto:lorenzo.paulatto@cnrs.fr"><lorenzo.paulatto@cnrs.fr></a>
<br>
To: <a class="moz-txt-link-rfc2396E" href="mailto:users@lists.quantum-espresso.org"><users@lists.quantum-espresso.org></a>
<br>
Subject: Re: [QE-users] oscillations in G(V) diagrams
<br>
Message-ID: <a class="moz-txt-link-rfc2396E" href="mailto:76693ba3-d502-65e2-005a-5a9b9aab1922@cnrs.fr"><76693ba3-d502-65e2-005a-5a9b9aab1922@cnrs.fr></a>
<br>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
<br>
<br>
Hello Jakob,
<br>
<br>
you do not give much detail about what you are doing. As said,
QHA is
<br>
effective when dealing with one degree of freedom (i.e. cubic
<br>
semiconductor) but harder to use in any other case. Are you
doing a
<br>
constant-volume variable-cell relax (aka cell_dofree='shape')
for a
<br>
series of volumes? And then computing for each volume the
Helmholtz free
<br>
energy (from the phonons directly or from the dos)? Are you
doing this
<br>
your self by hand or using one of the available QHA software
packages?
<br>
<br>
The oscillations could be an honest bug, or a difficult
integration of
<br>
the DOS.
<br>
<br>
cheers
<br>
<br>
<br>
On 04/11/2022 09:20, Jakob Kraus wrote:
<br>
<blockquote type="cite">Dear QE users,
<br>
<br>
<br>
I am trying to calculate heat capacities, and to this end, I
have
<br>
calculated the Gibbs energy as a function of volume
<br>
<br>
at several temperatures in a range of 0-700 K.
<br>
<br>
However, the functions that result from this do not show a
single
<br>
minimum, but rather a whole lot of oscillations, which
<br>
<br>
seem to originate from the phonons, since the E(V) diagram at
0 K
<br>
shows a single minimum as expected.
<br>
<br>
I am thankful for any help you can offer with getting rid of
these
<br>
oscillations.
<br>
<br>
I have attached input files and some plots to showcase the
problem.
<br>
<br>
<br>
Best regards,
<br>
<br>
<br>
Jakob Kraus, TU Freiberg
<br>
<br>
_______________________________________________
<br>
The Quantum ESPRESSO community stands by the Ukrainian
<br>
people and expresses its concerns about the devastating
<br>
effects that the Russian military offensive has on their
<br>
country and on the free and peaceful scientific, cultural,
<br>
and economic cooperation amongst peoples
<br>
_______________________________________________
<br>
Quantum ESPRESSO is supported by MaX (<a class="moz-txt-link-abbreviated" href="http://www.max-centre.eu">www.max-centre.eu</a>)
<br>
users mailing <a class="moz-txt-link-abbreviated" href="mailto:listusers@lists.quantum-espresso.org">listusers@lists.quantum-espresso.org</a>
<br>
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<br>
</blockquote>
</blockquote>
_______________________________________________
<br>
The Quantum ESPRESSO community stands by the Ukrainian
<br>
people and expresses its concerns about the devastating
<br>
effects that the Russian military offensive has on their
<br>
country and on the free and peaceful scientific, cultural,
<br>
and economic cooperation amongst peoples
<br>
_______________________________________________
<br>
Quantum ESPRESSO is supported by MaX (<a class="moz-txt-link-abbreviated" href="http://www.max-centre.eu">www.max-centre.eu</a>)
<br>
users mailing list <a class="moz-txt-link-abbreviated" href="mailto:users@lists.quantum-espresso.org">users@lists.quantum-espresso.org</a>
<br>
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<br>
</blockquote>
<div class="moz-signature">-- <br>
<small>Dr. Lorenzo Paulatto<br>
IdR @ IMPMC - CNRS UMR 7590 & Sorbonne Université<br>
phone: +33 (0)1 442 79822 / skype: paulatz<br>
<a href="http://www.impmc.upmc.fr/~paulatto/"
class="moz-txt-link-freetext">http://www.impmc.upmc.fr/~paulatto/</a>
- <a href="https://anharmonic.github.io/"
class="moz-txt-link-freetext">https://anharmonic.github.io/</a><br>
23-24/423 B115, 4 place Jussieu 75252 Paris CX 05<small></small></small></div>
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