[QE-users] "a" parameter in SYSTEM card

[dlduran at uco.es]

Dear all,

  I'm starting to study a perovskite and I am a bit confused about the  
parameter "a" of the SYSTEM card.

  According to the pw.x input page of QE this parameter must be in  
angstroms. I have a calculation in which, apparently, this parameter  
is in bohr:

&SYSTEM
  ibrav = 2
  a = 12.1616

  With these numbers, the calculation starts and finshes well.

  I have done the simple check of changing "a" to 6.0808. This last  
value should be angstroms and it should work, according to the webpage:

&SYSTEM
  ibrav = 2
  a = 6.0808

  But, this new calculation does not finish and blows up just after starting.

  For both of them, I have used:

CELL_PARAMETERS angstrom
  6.08 -4.10  0.00
  6.08 -4.10  0.00
-0.46  0.00 31.37

  ...

ATOMIC_POSITIONS crystal
Pb 0.45 0.06 0.04
Pb 0.06 0.45 0.54

  ...


  I don't know what is going on. The parameter "a" is in bohr or in angstroms?

  Thanks for your help, David.



--------------------------
David López Durán
Department of Physics
University of Córdoba, Spain
Phone: +34 957 21 20 32
https://es.linkedin.com/in/davidlopezduran