[Pw_forum] lattice instability and local minimum energy postion

[Paolo Giannozzi]

> [...]  I displaced atoms in the cell according 
> to the eigen-displacements shown above,and got a cubic cell containg 8 
> atoms. But I found the energy rised with the increase of atom 
> displacements, which was totally contrary to what I expected.

have you tried the same operation on a simpler system, such as e.g.
GaAs? You should get the phonon frequencies. If you don't, you
may have made a mistake

Paolo
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Paolo Giannozzi, Democritos and University of Udine, Italy