[Pw_forum] change of crystal symmetry during vc-relax calculations with pressure

[saqib javed]

Dear PWSCF users,

I have a question regarding vc-relaxation with bfgs. I am trying to optimize lattice parameters and atomic positions of unit cell at high pressures. while initial symmetry of unit cell is tetragonal (a=b), the optimized cell parameters at P=25 GPa seems to be in orthorhombic symmetry i.e., a and b lattice parameters are no more equal. Final cell paramteres are:

CELL_PARAMETER

0.9958000   0.0000000   0.000000
0.0000000   0.9929000   0.000000
0.0000000   0.0000000   1.405800 

Can vc-relaxation at a given pressure with bfgs method allows for change of crystal symmetry ?? I would appreciate a clarification

with best regards

Saqib Javaid
NCP, Pakistan. 
 		 	   		  
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