Hi,
Using qe-6.2.1 I was puzzled by some pw.x results obtained when using an
input file containing these lines:
....
&system
ibrav=-13,uniqueb=.true.
space_group=12
A=14.3100,B=6.3383,C=10.1995
cosAC=-0.70644
...
until I realized that the corresponding output contained these lines:
celldm(1)= 27.041981 celldm(2)= 0.442928 celldm(3)= 0.712753
celldm(4)= 0.000000 celldm(5)= 0.000000 celldm(6)= 0.000000
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:
.....
&system
ibrav=-13,uniqueb=.true.
space_group=12
A=14.3100,B=6.3383,C=10.1995
celldm(5)=-0.70644
.....
Then I get in output, as expected:
celldm(1)= 27.041981 celldm(2)= 0.442928 celldm(3)= 0.712753
celldm(4)= 0.000000 celldm(5)= -0.706440 celldm(6)= 0.000000
If I change the unit cell definition so that the unique axis is c, and
use ibrav=13 (with the default uniqueb=.false.) then cosAB is read
correctly. Not reading cosAC when 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.
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).
Regards,
--
José C. Conesa
Instituto de Catálisis y Petroleoquímica, CSIC
Marie Curie 2, Cantoblanco
28049 Madrid, Spain
Tel. (+34)915854766
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