[Pw_forum] Supercell totlal energy

Stefano de Gironcoli degironc at sissa.it
Fri Apr 29 08:58:36 CEST 2011

Dear Padmaja Patnaik
  if your cell contains 54 [=2*(3^3)] atoms it is likely a cell with an 
"a" constant three times the original one.
   then you should divide by 27 and if you want good matching with the 
original calculation your k-point grid should also be reduced by a 
factor of three.


On 04/28/2011 10:23 PM, Padmaja Patnaik wrote:
> Dear All
> My calculation involves a zinc blend structure . To generate a supercell I have expanded the lattice constant 'a' twice in all direction. This I have done using Exciting code (also known as Elk code). Which gives the primitive cell involving 54 atoms out of this expanded cell. The scf calculation in Quantum Espresso gives the total energy for this cell. If I want total energy/unit cell then dividing the value with 8 (since supercell has 8 unit cells) will give the correct total energy per unit cell. Am I right?
> Thanking you in advance,
> Regards
> Padmaja Patnaik
> Research Scholar
> Dept of Physics
> IIT Bombay
> Mumbai, India
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