[Wien] another space group question : hexagonal to orthorhombic

[Gilles Hug]

Dear all,

In order to make deformations, I have built an orthorhombic structure 
file (#63 Cmcm) which is equivalent to an hexagonal one (#194 P63/mmc).
The orthorhombic cell has double volume and is centered. The hex cell 
basis is (a, b=a, c) and the ortho (a, a+2b, c)/
I have extensively checked both structures and can't find difference.
They both have same volume, atoms are in same positions and all other 
parameters are identical (kpts, RMT, RKM,...).
In both cases the calculation runs smoothly.
However I get 0.1 Ryd difference in total energy between the two 
structures, which seems to me way too large.
I am puzzled.
I would appreciate if anyone has suggestions on which point to further 
check.
Cheers

Dr. Gilles Hug
LEM ONERA-CNRS
BP 72
92322 Châtillon
France
+33 1 46 73 45 42
gilles.hug at onera.fr