[Pw_forum] Question on stress in a system with constraints

Nicola Marzari marzari at MIT.EDU
Sat Oct 29 12:48:39 CEST 2005


Stefano de Gironcoli wrote:

> 
> Dear Nicola and Kostya,
> I did not think deeply about the question, so I may be wrong, but I agree
> with Kostya.
> 
> Stress is a first order derivative and as such only GS properties should
> be needed.
> 

Yes - apologies I forgot to correct this. For some reason I was
thinking at elastic constants, thus at second derivatives of the
energy. Bottom line - all my previous emails would be correct if you
were looking at an elastic constant. For stress, what Stefano and
Kostya said was right.

				nicola

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Prof Nicola Marzari   Department of Materials Science and Engineering
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