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<p><font face="Helvetica, Arial, sans-serif">Hi,</font></p>
<p><font face="Helvetica, Arial, sans-serif">Using qe-6.2.1 I was puzzled
by some </font><font face="Helvetica, Arial, sans-serif"><font
face="Helvetica, Arial, sans-serif">pw.x </font>results
obtained when using an input file containing these lines:</font></p>
<p><font face="Helvetica, Arial, sans-serif">....</font></p>
<p><font face="Helvetica, Arial, sans-serif"> &system<br>
ibrav=-13,uniqueb=.true.<br>
space_group=12<br>
A=14.3100,B=6.3383,C=10.1995<br>
cosAC=-0.70644<br>
...</font></p>
<p><font face="Helvetica, Arial, sans-serif">until I realized that
the corresponding output contained these lines:</font></p>
<p><font face="Helvetica, Arial, sans-serif"> celldm(1)=
27.041981 celldm(2)= 0.442928 celldm(3)= 0.712753<br>
celldm(4)= 0.000000 celldm(5)= 0.000000 celldm(6)=
0.000000<br>
</font></p>
<p><font face="Helvetica, Arial, sans-serif">That is, the monoclinic
angle was not taken into account. Giving the angle parameter
with cosAB or cos BC changed nothing. I only could obtain the
correct resullts using an input file with these lines:<br>
</font></p>
<p>.....<br>
<font face="Helvetica, Arial, sans-serif"><font face="Helvetica,
Arial, sans-serif"> &system<br>
ibrav=-13,uniqueb=.true.<br>
space_group=12<br>
A=14.3100,B=6.3383,C=10.1995<br>
celldm(5)=-0.70644</font></font></p>
<p><font face="Helvetica, Arial, sans-serif"><font face="Helvetica,
Arial, sans-serif">.....<br>
</font></font></p>
<p><font face="Helvetica, Arial, sans-serif"><font face="Helvetica,
Arial, sans-serif">Then I get in output, as expected:</font></font></p>
<p><font face="Helvetica, Arial, sans-serif"><font face="Helvetica,
Arial, sans-serif"> celldm(1)= 27.041981 celldm(2)=
0.442928 celldm(3)= 0.712753<br>
celldm(4)= 0.000000 celldm(5)= -0.706440
celldm(6)= 0.000000</font></font></p>
<p><font face="Helvetica, Arial, sans-serif"><font face="Helvetica,
Arial, sans-serif">If I change the unit cell definition so
that the unique axis is c, and use </font></font><font
face="Helvetica, Arial, sans-serif"><font face="Helvetica,
Arial, sans-serif"><font face="Helvetica, Arial, sans-serif"><font
face="Helvetica, Arial, sans-serif">ibrav=13 (with the
default </font></font></font></font><font
face="Helvetica, Arial, sans-serif"><font face="Helvetica,
Arial, sans-serif"><font face="Helvetica, Arial, sans-serif"><font
face="Helvetica, Arial, sans-serif"><font face="Helvetica,
Arial, sans-serif">uniqueb=.false.</font></font></font>)
then cosAB is read correctly. Not reading cosAC when </font></font><font
face="Helvetica, Arial, sans-serif"><font face="Helvetica,
Arial, sans-serif"><font face="Helvetica, Arial, sans-serif">ibrav=-13
is obviously a bug that should be corrected. I did not
verify (yet) if the same problem occurs with ibrav=-12, but
I suspect it may occur also. If some problem occurs also for
other negative ibrav values, I do not know.</font></font></font></p>
<p><font face="Helvetica, Arial, sans-serif"><font face="Helvetica,
Arial, sans-serif"><font face="Helvetica, Arial, sans-serif">By
the way, when explaining the different ibrav values the
manual should include a mention (now absent) to the
possibility of having ibrav=-13, and when explaining both
ibrav=-12 and ibrav=-13 it should be said, at that same
place, that one must add uniqueb=.true. (although actually
specifying uniqueb should not be necessary, it might be
adopted automatically by the program when these two negative
ibrav values are detected).</font></font></font></p>
<p><font face="Helvetica, Arial, sans-serif"><font face="Helvetica,
Arial, sans-serif"><font face="Helvetica, Arial, sans-serif">Regards,<br>
</font></font></font></p>
<pre class="moz-signature" cols="72">--
José C. Conesa
Instituto de Catálisis y Petroleoquímica, CSIC
Marie Curie 2, Cantoblanco
28049 Madrid, Spain
Tel. (+34)915854766</pre>
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