Dear all,
I try to use Elastic and quantum-espresso to calculate wurtzite structure of AlN. the input file is :
&SYSTEM
ibrav= 4, celldm(1)= 5.9090, nat= 4, ntyp= 2,
celldm(3) = 1.6034
ecutwfc = 120
ATOMIC_POSITIONS crystal
Al 0.00 0.00 0.00
Al 0.3333 0.6666 0.5
N 0.00 0.00 0.345
N 0.3333 0.6666 0.845
run Elastic_Setup_ESPRESSO then get that :
Number and name of space group: 36 (C m c 21)
Orthorhombic structure in the Laue classification.
This structure has 9 independent second-order elastic constants.
…. Oops ERROR: ibrav = 4, It means "Hexagonal" structure.
But this structure can be represented by "Orthorhombic" system.
THEY ARE NOT COMPATIBLE. Please Look at sgroup.out
I found that when I change the ATOMIC_POSITIONS to
Al 0.00 0.00 0.00
Al 0.0 0.0 0.5
N 0.00 0.00 0.345
N 0.0 0.0 0.845
the output will be right like:
Number and name of space group: 183 (P 6 m m)
Hexagonal I structure in the Laue classification.
This structure has 5 independent second-order elastic constants.
How can i get the right structure with Elastic?
Thank you!!!!!!