[Pw_forum] lattice constant from unit cell vs. from supercell

[Paolo Giannozzi]

Chad Junkermeier wrote:

> If I do this using the unit cell, everything seems to 
> work correctly, and the equilibrium lattice constant for the system 
> seems to be correct.  If, instead, I use a 2x2 supercell I find that 
> the equilibrium lattice constant is not the same (or even close) to the 
> unit cell result.

your data are for fixed-cell structural optimization: what do you mean
by "the equilibrium lattice constant is not the same"? You choose the
lattice constant

P.
-- 
Paolo Giannozzi, Democritos and University of Udine, Italy