[Pw_forum] Access to 2nd order derivatives

[Paolo Giannozzi]

On Mar 14, 2007, at 22:00 , Marcel Mohr wrote:

> I wonder if it is possible to obtain the 2nd derivative of the  
> total energy
> for a user defined set of atomic coordinates (not a real but  
> infinitely
> small displacement from the ground state).

in principle, it is, and once upon a time it was possible.
Now there is the 'single mode calculation' (example 02),
in which you can choose a specific displacement pattern,
but only among those automatically computed by the code.

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