[Wien] another space group question : hexagonal to orthorhombic

Gilles Hug gilles.hug at onera.fr
Wed Jan 21 17:37:27 CET 2004

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 

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

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