<div dir="ltr">Dear David, <div>the value of a is definitely in Angstrom (<a href="https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm258">https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm258</a>).</div><div>If with 12 A it works and with 6 A it does not work, this means that maybe your unit cell with 6 A side is not able</div><div>to accommodate the atoms (this could be inferred only if you provided the whole input).</div><div><br></div><div>Let me also point out that, as far as the CELL_PARAMETERS card is concerned, you should (maybe) find in the output</div><div>(at the beginning) a message saying that it has been ignored. Indeed, if you DO specify ibrav >0, the unit cell vectors</div><div>are chosen by the code with the parameters given in input (<a href="https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm224">https://www.quantum-espresso.org/Doc/INPUT_PW.html#idm224</a>),</div><div>whereas the input from the CELL_PARAMETERS ard is allowed only with ibrav = 0.</div><div><br></div><div>Generally speaking, it is worth visualizing the input (using for example XCrysDen able to directly open QE input files) before</div><div>attempting any calculation.</div><div><br></div><div>Giovanni</div><div><br clear="all"><div><div dir="ltr" class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><span style="color:rgb(0,0,0)">-- <br><br>Giovanni Cantele, PhD<br>CNR-SPIN<br>c/o Dipartimento di Fisica<br>Universita' di Napoli "Federico II"<br>Complesso Universitario M. S. Angelo - Ed. 6<br>Via Cintia, I-80126, Napoli, Italy<br><a href="mailto:giovanni.cantele@spin.cnr.it" style="color:rgb(17,85,204)" target="_blank">e-mail: giovanni.cantele@spin.cnr.it</a><br>Phone: +39 081 676910<br>Skype contact: giocan74<br><br>ResearcherID: <a href="http://www.researcherid.com/rid/A-1951-2009" style="color:rgb(17,85,204)" target="_blank">http://www.researcherid.com/rid/A-1951-2009</a><br>Web page: </span><a href="https://sites.google.com/view/giovanni-cantele/home" style="color:rgb(17,85,204)" target="_blank">https://sites.google.com/view/giovanni-cantele/home</a><br></div></div></div><br></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Il giorno sab 8 lug 2023 alle ore 13:28 <<a href="mailto:dlduran@uco.es">dlduran@uco.es</a>> ha scritto:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">Dear all,<br>
<br>
I'm starting to study a perovskite and I am a bit confused about the <br>
parameter "a" of the SYSTEM card.<br>
<br>
According to the pw.x input page of QE this parameter must be in <br>
angstroms. I have a calculation in which, apparently, this parameter <br>
is in bohr:<br>
<br>
&SYSTEM<br>
ibrav = 2<br>
a = 12.1616<br>
<br>
With these numbers, the calculation starts and finshes well.<br>
<br>
I have done the simple check of changing "a" to 6.0808. This last <br>
value should be angstroms and it should work, according to the webpage:<br>
<br>
&SYSTEM<br>
ibrav = 2<br>
a = 6.0808<br>
<br>
But, this new calculation does not finish and blows up just after starting.<br>
<br>
For both of them, I have used:<br>
<br>
CELL_PARAMETERS angstrom<br>
6.08 -4.10 0.00<br>
6.08 -4.10 0.00<br>
-0.46 0.00 31.37<br>
<br>
...<br>
<br>
ATOMIC_POSITIONS crystal<br>
Pb 0.45 0.06 0.04<br>
Pb 0.06 0.45 0.54<br>
<br>
...<br>
<br>
<br>
I don't know what is going on. The parameter "a" is in bohr or in angstroms?<br>
<br>
Thanks for your help, David.<br>
<br>
<br>
<br>
--------------------------<br>
David López Durán<br>
Department of Physics<br>
University of Córdoba, Spain<br>
Phone: +34 957 21 20 32<br>
<a href="https://es.linkedin.com/in/davidlopezduran" rel="noreferrer" target="_blank">https://es.linkedin.com/in/davidlopezduran</a><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 href="http://www.max-centre.eu" rel="noreferrer" target="_blank">www.max-centre.eu</a>)<br>
users mailing list <a href="mailto:users@lists.quantum-espresso.org" target="_blank">users@lists.quantum-espresso.org</a><br>
<a href="https://lists.quantum-espresso.org/mailman/listinfo/users" rel="noreferrer" target="_blank">https://lists.quantum-espresso.org/mailman/listinfo/users</a><br>
</blockquote></div>