thank you very much for your answer. are you explicitly using the space group and Wyckoff positions? and are you getting wrong positions? or just a funny set of alpha beta gamma angles?
I used the crystal axes explicitly to reconstruct the primitive crystal from the output file only and I got this strange behavior of alpha and beta angles being the complementary of the expected ones, i.e.70.53 instead of 180-70.53=109.74 deg. kind regards, Mihalis Kavousanakis On 25/1/2017 3:58 μμ, Paolo Giannozzi wrote: > On Wed, Jan 25, 2017 at 8:48 AM, Mihalis Kavousanakis > <[email protected]> wrote: >> Dear all, >> >> I have a question regarding ibrav=3 crystal axes, which are reported as >> v1=(a/2)(1,1,1), v2=(a/2)(-1,1,1), v3=(a2/2)(-1,-1,1) >> >> Should these be rather: >> v1=(a/2)(-1,1,1), v2=(a/2)(1-,1,1), v3=(a2/2)(1,1,-1) ? > they should, but they aren't, for reasons nobody knows any longer > since many years (that part of the code likely dates back to the > 70's). Unfortunately it is not possible to change it without breaking > existing input data. The only thing one might do is to add a > "ibrav=-3" case with a more sensible choice of axis. > >> I encountered this problem when I performed an scf simulation on a >> Molybdenum Im-3m crystal in its primitive form. >> The crystal's dimensions are a=b=c=2.725Angstrom, and >> alpha=beta=gamma=109.47 deg. >> >> The crystal axes as reported in the output file however would give: >> a=b=c=2.725Angstrom, and alpha=beta=70.53deg, beta=109.47 deg. > are you explicitly using the space group and Wyckoff positions? and > are you getting wrong positions? or just a funny set of alpha beta > gamma angles? > > Paolo > >> I am runnning on QE 5.2.1 >> >> >> kind regards, >> Mihalis Kavousanakis >> >> _______________________________________________ >> Pw_forum mailing list >> [email protected] >> http://pwscf.org/mailman/listinfo/pw_forum > > _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
