<div dir="ltr"><div><p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">Dear developer, </p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"> </p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">I have vc-relaxed Hf7O8N4 (hafnium oxynitride) assuming the
crystal to be rhombohedra with a=b, alpha=beta=90 deg, and gamma=120 deg. So, I
used ibrav=4 and gave A,B,C, cosAB, cosAC and cosBC values. Part of the input
looks as follows:</p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"> </p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i>&system</i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i> ibrav=
4
</i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i> A=9.4851, B=9.4851, C=8.7867,
cosAB=-0.5, cosAC=0.0, cosBC=0.0</i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i> nat=19 , ntyp= 3,</i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i> ecutwfc =70, ecutrho= 840, </i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i> occupations= 'fixed', </i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i> nbnd= 100 </i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"> </p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">The vc-relax ran successfully and I got the following
output:</p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"> </p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i>Final enthalpy = -5322.7186767755 Ry</i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i>Begin final coordinates</i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i> new unit-cell volume
= 1536.19292 a.u.^3 ( 227.64030 Ang^3 )</i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i> </i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i>CELL_PARAMETERS (alat= 17.92424134)</i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i> 0.638651125 0.103631841
-0.047929083</i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i> -0.235833337 0.630643088
-0.049740867</i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"><i> -0.043220738 -0.085864416
0.635634338</i></p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"> </p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">Here, the output cell_parameter values are not consistent
with the input. I assumed it as ibrav=4 (hex or rhombohedra), but if I use the
output cell_parameter and calculated the final value (using the vector formulas
for ibrav=4 from pw.x documentation) for lattice constant ‘a’, I will get
different values from different vectors. So, my question is how do we analyse
such a system in which we give certain crystal structure as an input and the
vc-relax runs successfully (<b><i>does not crash</i></b>) and give an output
which isn’t consistent with the input crystal system? Can I accept the results
and carry on further because the vc-relax did not crash meaning that everything
is fine?</p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"> </p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">Please help me in this regard.</p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"> </p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">Kind regards,</p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif"> </p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">Bharat Thapa</p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">PhD student</p>
<p class="MsoNormal" style="margin:0cm 0cm 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif">UNSW</p></div></div>