[Pw_forum] Crash in routine set_sym_bl

Paolo Giannozzi paolo.giannozzi at uniud.it
Fri Feb 13 14:38:15 CET 2015

On Fri, 2015-02-13 at 11:23 +0100, Sergi Vela wrote:

> "Error in routine set_sym_bl (1): Symmetry group not a group!

this is the error

>  Use standard orientations for axis"

and this is a hint. One known case in which this happens is for
hexagonal lattices with a basal crystal axis rotated of 15 degrees
wrt to the cartesian axis.
In your case, it happens (I think) because you choose these axis:

  0.85244126841036916        0.0000000000000000        0.000000
 -0.42622032521263958       0.73823597207445180        0.000000
  3.13916478650538062E-007  5.43719027573123104E-007   1.000000

that are very close but not exactly equal to what you wanted:
 a 0 0 
-a/2 2a/sqrt(3)
 0 0 c
so some symmetry operations that should be there, aren't found

> One piece of information: I am running it with QE v.5.1.1. When I run
> it using version 4.2.1 I don't get any error. 

because v.4.2.1 didn't check if the group is a group. It is not needed
in most cases, but for some calculations it is


> Any help is appreciated. Thanks!
> Sergi Vela, 
> University of Strasbourg
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